NCHurricane2009's Blog

2012 Atlantic Hurricane Season Birdseye Discussion #67

By: NCHurricane2009, 7:48 AM GMT on July 31, 2012

...JULY 31 2012...3:50 AM EDT...
Disturbance in eastern tropical Atlantic has been upgraded to Invest 99-L...but is slowly organizing (see paragraph P8).

Elsewhere...new frontal disturbance offshore of Carolinas showing no signs of tropical development (see end of paragraph P1). Both tropical waves currently in the Caribbean Sea have become more impressive...but neither are showing signs of tropical development (paragraphs P6 and P7).

Of side note...if no Atlantic tropical cyclone develops in the next 24 hours...this will be the first July since 2009 with no July Atlantic tropical cyclone activity.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...

This chart is generated based on surface analysis from the National Hurricane Center TAFB at 1800Z, and the 1919Z-released HPC analysis.

In light blue is upper air analysis, with 200 mb wind barbs calculated by GOES satellite imagery showing the upper-level wind direction. Based on the 200 mb wind barbs, blue-dashed lines are locations of upper troughs, blue-zig-zag lines are locations of upper ridges. Blue Ls are locations of upper lows, blue Hs are locations of upper ridges.

In red is surface analysis, with solid lines indicating locations of surface fronts, dashed lines indicating locations of surface troughs, and zig-zag lines indicating surface ridge axes. Ls indicate surface lows, Hs indicate surface highs.

...THERMODYNAMICS BIRDSEYE CHART...

This chart is generated using GOES water vapor satellite imagery. Brown indicates dry air. White, blue, and purple indicates moist air. An increase in moisture indicates slower air parcel lapse rates with elevation and hence an increase toward instability.

Sea-surface temperatures are overlaid with light blue isotherms. The 26 deg C isotherm is highlighted in red. Waters at and south of the 26 deg C isotherm indicate low-level warmth and hence faster environmental lapse rates with elevation (more instability). Waters north of the 26 deg C isotherm indicate slower environmental lapse rates with elevation (less instability).

...MID-LATITUDES DISCUSSION...
P1...Longwave upper trough regime across eastern North America is spreading into the high seas of the Atlantic...with low-level warm air advection ahead supporting a west Atlantic upper ridge...while another upper ridge builds behind over the SW US. Hudson Bay surface cyclone has diminished while its upper trough is in E Canada. Another upper trough is swinging in from Hudson Bay...supporting a new 1004 to 1006 mb frontal depression just south of Hudson Bay. Convergence between this longwave upper trough regime and SW US upper ridge supports a 1020 to 1018 mb west US surface ridge...while a 1020 mb surface ridge from NE US to Atlantic Canada is supported by upper convergence on the back sides of embedded shortwave upper troughs. Accelerationally divergent westerly jet on north side of SW US upper ridge appears to support a disorganized 1010 mb frontal depression over the central US. Frontal depression S of Greenland is heading ENE to Europe...and frontal depression offshore of Massachusetts is now offshore of Newfoundland. S Greenland frontal depression has weakened to 1010 mb without support of a shortwave upper trough. Finally...shortwave upper trough over SE US supports frontal depression activity along the coast of the Carolinas...which showed impressive t-storms ventilating into the W lobe of W Atlantic upper ridge. This activity is not as impressive this early morning...resembling more of a non-tropical system heading NE toward cooler waters and NE US shoreline.

P2...Upper trough east of Greenland has moved into Europe. It leaves behind fractures east of W Atlantic upper ridge...including upper vortex just SE of the Azores...and mid-ocean upper vortex. Divergence east of the upper vortex SE of the Azores supports surface troughing over Spain...marked with a surface low and trough as of 1800Z TAFB.

P3...Cut-off upper vorticity in the Caribbean Sea consists of an upper vortex over Cuba with upper trough extending to the southeast.

P4...Atlantic surface ridge of 1019 to 1022 mb centers is supported by a few upper convergent sources while stretching from the Gulf of Mexico to the waters offshore of west Europe....including convergence SE of the of the SW US and west Atlantic upper ridges in paragraph P1. South side of this surface ridge is helping to waft Africa desert dry air westward across the Atlantic tropics. However...this dry air appears to be reducing due to enhancement of tropical waves as described in paragraphs P5....P7....and P8. Within this surface ridge...a mid-ocean surface 1016 mb low has popped up with supportive upper divergence between mid-ocean upper vortex in paragraph P2 and W Atlantic upper ridge in paragraph P1. A 1022 mb low has popped up S of the Azores with supportive divergence between the two cut-off upper vortices mentioned in paragraph P2.

...TROPICAL BELT DISCUSSION...
P5...East tropical Atlantic upper ridge has shifted southward over the tropical waves in paragraphs P7 and P8. This shift is due to southward dig of upper fractures mentioned in paragraph P2. The tropical wave t-storm activity has locally inflated the upper ridge into cells of upper anticyclonic outflow. Upper vortex N of the Lesser Antilles...once embedded in this upper ridge...has tracked NW to waters SW of Bermuda while orbiting W Atlantic upper ridge in paragraph P1. Upper vorticity west of the upper ridge...located in the south Gulf of Mexico...is weakening to the south of the SW US upper ridge in paragraph P1. South-central Caribbean upper ridge continues enhancing Central America area t-storms and t-storms associated with the tropical wave in paragraph P6...and struggles to link with this east Atlantic upper ridge due to upper vorticity in paragraph P3.

P6...Tropical wave moving across central Caribbean is pushing into central America. It has seen a tremendous increase in t-storm activity in the last 24 hours thanks to boosted outflow from south-central Caribbean upper ridge in paragraph P5. The tropical wave is currently speeding westward away from the t-storm activity...and no signs of tropical cyclone development are occurring in this area. No current computer models are suggesting tropical development.

P7...Tropical wave nearing the Lesser Antilles has crossed the islands into the eastern Caribbean Sea. Associated t-storm activity continues to increase as it has established upper anticyclonic outflow as mentioned in paragraph P5. No signs of tropical cyclone development are occurring in this area. No current computer models are suggesting tropical development.

P8...Tropical wave southwest of the Cape Verde Islands has been upgraded to Invest 99-L. Its surface low pressure is marked at 1009 mb as of 1800Z NHC TAFB. This surface low and t-storms has favorable conditions thanks to established upper anticyclonic outflow as mentioned in paragraph P5. National Hurricane Center Outlook suggests 20% chance of tropical cyclone formation here in next 48 hours. The CMC model still shows a stronger tropical cyclone tracking more WNW toward northern Lesser Antilles and passing near or north of the Bahamas. The GFS model still shows a weaker tropical cyclone tracking more W into the Lesser Antilles and Caribbean. The faster this develops...the more deep-layered the system becomes such that SW-retrograding upper vorticity (paragraph P2) pulls this system more north (like the CMC model). I am leaning toward a more southern solution straight toward the Lesser Antilles (like the GFS) due to the rather slow rate of organization of the disturbance currently observed. I am not yet upgrading this to a special feature on this blog until the disturbance shows a more imminent trend of becoming a tropical cyclone.

P9...Based on satellite...tropical wave rolling off of Africa in the previous discussion I now estimate to be south of the Cape Verde Islands. This tropical wave has not yet been acknowledged by NHC TAFB. Satellite imagery suggests the tropical wave is under northerly shear thanks to upper anticyclonic outflow of neighboring wave in paragraph P8.

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2012 Atlantic Hurricane Season Birdseye Discussion #66

By: NCHurricane2009, 9:45 PM GMT on July 29, 2012

...JULY 29 2012...5:50 PM EDT...
Watching tropical disturbance in the eastern tropical Atlantic (see paragraph P9). This is the last chance of a July Atlantic tropical cyclone this year.

Of side note...if no Atlantic tropical cyclone develops before August 1...this will be the first July since 2009 with no July Atlantic tropical cyclone activity.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...

This chart is generated based on surface analysis from the National Hurricane Center TAFB at 1200Z, and the 1332Z-released HPC analysis.

In light blue is upper air analysis, with 200 mb wind barbs calculated by GOES satellite imagery showing the upper-level wind direction. Based on the 200 mb wind barbs, blue-dashed lines are locations of upper troughs, blue-zig-zag lines are locations of upper ridges. Blue Ls are locations of upper lows, blue Hs are locations of upper ridges.

In red is surface analysis, with solid lines indicating locations of surface fronts, dashed lines indicating locations of surface troughs, and zig-zag lines indicating surface ridge axes. Ls indicate surface lows, Hs indicate surface highs.

...THERMODYNAMICS BIRDSEYE CHART...

This chart is generated using GOES water vapor satellite imagery. Brown indicates dry air. White, blue, and purple indicates moist air. An increase in moisture indicates slower air parcel lapse rates with elevation and hence an increase toward instability.

Sea-surface temperatures are overlaid with light blue isotherms. The 26 deg C isotherm is highlighted in red. Waters at and south of the 26 deg C isotherm indicate low-level warmth and hence faster environmental lapse rates with elevation (more instability). Waters north of the 26 deg C isotherm indicate slower environmental lapse rates with elevation (less instability).

...MID-LATITUDES DISCUSSION...
P1...Longwave upper trough regime persists across eastern North America...with low-level warm air advection ahead supporting a west Atlantic upper ridge...while another upper ridge builds behind over the SW US. Hudson Bay surface cyclone and north Canada upper trough are gradually shifting east. Convergence between this north Canada upper trough and SW US upper ridge supports a 1021 mb west US surface ridge...while a 1020 to 1021 mb surface ridge from the Great Lakes to east Canada is supported by upper convergence on the back side of this longwave upper trough regime. Accelerationally divergent westerly jet on north side of SW US upper ridge appears to support a disorganized 1009 to 1011 mb frontal depression near the Dakotas and Manitoba. Newfoundland frontal depression has moved NE to waters S of Greenland...and NE US frontal depression has moved to waters offshore of Massachusetts. S Greenland frontal depression intensified from 1006 to 1003 mb in last 24 hrs while taking advantage of eastern divergence of a shortwave upper trough impulse in the longwave.

P2...Upper trough east of Greenland is approaching western Europe. Divergence east of this upper trough supports surface troughing over Spain...marked with a 1012 mb low pressure center as of 1200Z NHC TAFB map. South end of upper trough is fracturing to the east of the W Atlantic upper ridge in paragraph P1. Fracture includes upper vortex just SE of the Azores...and shortwave upper troughs WNW of the Cape Verde Islands.

P3...Cut-off upper vorticity in the central Caribbean Sea consists of an upper vortex over Cuba and upper vortex just SW of Jamaica.

P4...Atlantic surface ridge of 1019 to 1025 mb centers is supported by a few upper convergent sources while stretching from the Gulf of Mexico/SE US to the waters offshore of west Europe....including convergence SE of the of the SW US and west Atlantic upper ridges in paragraph P1. In conjunction with the south side of the upper ridge in paragraph P6...south side of this surface ridge is helping to waft Africa desert dry air westward across the Atlantic tropics.

...TROPICAL BELT DISCUSSION...
P5...Texas inverted upper trough had dissipated.

P6...East tropical Atlantic upper ridge persists...spanning from west Africa to the east Caribbean. Upper vorticity west of the upper ridge...located in the Gulf of Mexico...is weakening to the south of the SW US upper ridge in paragraph P1. South-central Caribbean upper ridge continues enhancing Central America area t-storms...and struggles to link with this east Atlantic upper ridge due to upper vorticity in paragraph P3. Upper vorticity remains embedded in this east Atlantic upper ridge with a series of inverted upper troughs. Upper vortex just north of the Lesser Antilles is retrograding westward about W Atlantic upper ridge in paragraph P1...and inverted upper trough SW of the Cape Verde Islands is now midway between the Cape Verdes and Lesser Antilles. Yet another inverted upper trough has developed just SE of the Lesser Antilles (see paragraph P8 for details).

P7...Tropical wave in the eastern Caribbean remains suppressed by dry air as it heads into the central Caribbean. Source of dry air mentioned in paragraph P4.

P8...Tropical wave midway between the Cape Verde Islands and Lesser Antilles is now nearing the Lesser Antilles. Surface low pressure spin evident in past days had dissipated...but associated t-storm activity has increased. This is due to upper divergence on the west flank of inverted upper trough midway between Cape Verdes and Lesser Antilles (paragraph P6). Increase in t-storms is also due to upper ridge axis in paragraph P6 shifting southward over the tropical wave and enhancing its upper outflow. Recent shift in upper ridge axis is due to southward dig of upper fractures mentioned in paragraph P2. Latent heat release of t-storms is locally inflating the upper ridge axis...creating an inverted upper trough just SE of the Lesser Antilles which is a manifestation of relatively lower upper atmo pressures west of the latent-heat-release driven upper ridge inflation.

P9...Suspect tropical wave is marked with a 1011 mb ITCZ low southwest of the Cape Verde Islands. This feature is still not designated an official tropical wave in NHC tropical weather discussion. Easterly vertical shear over the tropical wave has diminished as the upper ridge axis in paragraph P6 has shifted southward over the tropical wave (shift due to southward dig of upper fractures mentioned in paragraph P2). This has allowed the low pressure spin of the tropical wave to receive enhanced upper outflow from the upper ridge axis...and this disturbance became intermittently organized. CMC and GFS computer models are beginning to suggest tropical cyclone formation from this system. Other than adjacent dry air mentioned in paragraph P4...this system is in favorable conditions. Coupled with developing computer model support...this system bears watching as it heads toward the Lesser Antilles this week.

P10...Satellite imagery suggests the next tropical wave is emerging from Africa (see lower-right corner of above atmo birdseye chart).

Updated: 5:46 AM GMT on July 30, 2012

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2012 Atlantic Hurricane Season Birdseye Discussion #65

By: NCHurricane2009, 11:19 PM GMT on July 28, 2012

...JULY 28 2012...7:30 PM EDT...
Although tropical wave activity is gradually becoming more impressive (paragraphs P9 and P10)...none are showing signs of development. Atlantic tropics remain quiet as we head into the month of July's end.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...

This chart is generated based on surface analysis from the National Hurricane Center TAFB at 1200Z, and the 1327Z-released HPC analysis.

In light blue is upper air analysis, with 200 mb wind barbs calculated by GOES satellite imagery showing the upper-level wind direction. Based on the 200 mb wind barbs, blue-dashed lines are locations of upper troughs, blue-zig-zag lines are locations of upper ridges. Blue Ls are locations of upper lows, blue Hs are locations of upper ridges.

In red is surface analysis, with solid lines indicating locations of surface fronts, dashed lines indicating locations of surface troughs, and zig-zag lines indicating surface ridge axes. Ls indicate surface lows, Hs indicate surface highs.

...THERMODYNAMICS BIRDSEYE CHART...

This chart is generated using GOES water vapor satellite imagery. Brown indicates dry air. White, blue, and purple indicates moist air. An increase in moisture indicates slower air parcel lapse rates with elevation and hence an increase toward instability.

Sea-surface temperatures are overlaid with light blue isotherms. The 26 deg C isotherm is highlighted in red. Waters at and south of the 26 deg C isotherm indicate low-level warmth and hence faster environmental lapse rates with elevation (more instability). Waters north of the 26 deg C isotherm indicate slower environmental lapse rates with elevation (less instability).

...MID-LATITUDES DISCUSSION...
P1...Frontal systems and associated upper troughs mentioned in paragraphs P1...P2...and P3 of the previous discussion have merged into a longwave North America upper trough regime. Low-level warm air advection ahead has pushed the SE US upper ridge into the west Atlantic...while another upper ridge builds behind over the SW US. 3-day Animation of HPC maps suggests an upper trough and associated surface cyclones have been spinning over northern Canada...one such 1004 mb cyclone entering the picture from Hudson Bay. Convergence between this north Canada upper trough and SW US upper ridge supports a 1020 mb west US surface ridge...while a 1023 mb surface ridge from the Great Lakes to east Canada is supported by upper convergence on the back side of this longwave upper trough regime. Accelerationally divergent westerly jet on north side of SW US upper ridge appears to support a disorganized 1011 mb frontal depression near the Dakotas. NE US frontal depression (paragraph P1 of prev discussion) has split into two impulses...one traveling from New York State to Newfoundland and weakening from 1002 to 1009 mb in last 36 hours...second developing over the Great Lakes and currently 1011 mb in NE US. E Newfoundland surface frontal cyclone (paragraph P2 of prev discussion) has weakened to 1006 mb and moved north into S Greenland in last 36 hrs...while the frontal depression it left behind E of Bermuda had dissipated expect for a surface trough SW of Bermuda showing t-storm activity supported by directional divergence on the SW quad of W Atlantic upper ridge. Finally...surface cyclone near NE Hudson Bay coast (paragraph P3 of prev discussion) was absorbed by west side of aforementioned 1006 mb cyclone in last 36 hrs.

P2...Upper trough is still east of Greenland and amplified...thanks to amplified North Atlantic upper ridge to its west which continues to get support from low-level southerly warm air advection ahead of various frontal depressions/cyclones mentioned in paragraph P1 above. Divergence east of this upper trough supports surface troughing over Spain...marked with a 1010 mb low pressure center as of 1200Z NHC TAFB map. Satellite imagery suggests a cold front from the north is digging southward in this upper trough (see above-right corner of above atmo birdseye chart).

P3...Cut-off upper vorticity in the central Caribbean Sea has retrograded NW into Cuba as an upper vortex in the last 36 hours...steered by large west Atlantic upper ridge mentioned in paragraph P1.

P4...Atlantic surface ridge of 1019 to 1026 mb centers is supported by a few upper convergent sources while stretching from the Gulf of Mexico/SE US to the waters offshore of west Europe....including convergence SE of the of the SW US and west Atlantic upper ridges in paragraph P1...and convergence east of North Atlantic upper ridge (paragraph P2). In conjunction with the south side of the upper ridge in paragraph P6...south side of this surface ridge is helping to waft Africa desert dry air westward across the Atlantic tropics.

...TROPICAL BELT DISCUSSION...
P5...Cut-off upper vortex over south Texas has weakened into an inverted upper trough on the south side of SW US upper ridge mentioned in paragraph P1.

P6...East tropical Atlantic upper ridge persists...now spanning from west Africa to the east Caribbean. Upper vorticity west of the upper ridge...located in the SE Gulf of Mexico...now dominates most of the Gulf. In the wake of this upper vorticity...a south-central Caribbean upper ridge is enhancing t-storms over the Panama area...and an east-west upper trough left behind by Cuba upper vortex (paragraph P3) is struggling to allow the south-central Caribbean upper ridge to link with this east Atlantic upper ridge. Upper vorticity SW of the Canary Islands has merged with upper trough in paragraph P2...but upper vorticity remains embedded in this east Atlantic upper ridge with a series of inverted upper troughs on its south side. Inverted upper trough nearing the Lesser Antilles in prev discussion is now an upper vortex just NE of those islands...while inverted upper trough west of the Cape Verde Islands is now a dissipating upper vortex midway between the Cape Verdes and Lesser Antilles. Yet another inverted upper trough has developed SW of the Cape Verde Islands (see paragraph P10 for details).

P7...Tropical wave over SE Mexico is exiting the picture into the eastern Pacific while still suppressed by Gulf of Mexico upper vorticity mentioned in paragraph P6. Therefore...this is the last statement on this tropical wave on this blog.

P8...Tropical wave nearing the Lesser Antilles in the previous discussion is now crossing those islands into the eastern Caribbean. The tropical wave remains suppressed by dry air mentioned in paragraph P4. NHC TAFB maps suggest the north end of this tropical wave is fracturing into a surface trough.

P9...Tropical wave west of the Cape Verde Islands in the prev discussion is now midway between the Cape Verdes and Lesser Antilles. Satellite animation still suggests a surface low pressure spin...but the wave continues to struggle with dry air mentioned in paragraph P4. The inverted upper trough over the tropical wave has become a dissipating upper vortex just to its west (see paragraph P6)...which allowed for a slight increase in t-storms over the low pressure spin...especially due to upper divergence on the west flank of new inverted upper trough SW of the Cape Verde Islands (see paragraphs P6 and P10 for details on new inverted upper trough).

P10...During the previous discussion...satellite imagery suggested the next tropical wave was rolling off of Africa...and satellite imagery now suggests this tropical wave should now be SSW of the Cape Verde Islands. The NHC TAFB maps added a 1014 mb ITCZ low at 1200Z today...located south of the Cape Verde Islands...but the NHC tropical weather discussion still is not calling this a tropical wave. Extesnive t-storm activity from the tropical wave has generated latent heat release that is trying to inflate the east end of the upper ridge in paragraph P6. Because most of this release has been south of the upper ridge axis...this has accelerated the speed of easterly upper winds in the area...hence increasing the easterly vertical shear over the tropical wave. An inverted upper trough has formed SW of the Cape Verde Islands...a manifestation of relatively lower upper atmo pressures west of the latent-heat-release driven upper ridge inflation.

Updated: 5:21 AM GMT on October 08, 2012

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2012 Atlantic Hurricane Season Birdseye Discussion #64

By: NCHurricane2009, 10:33 AM GMT on July 27, 2012

...JULY 27 2012...6:35 AM EDT...
Atlantic tropics all clear as we head into the end of July.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...

This chart is generated based on surface analysis from the National Hurricane Center TAFB at 0600Z, and the 0725Z-released HPC analysis.

In light blue is upper air analysis, with 200 mb wind barbs calculated by GOES satellite imagery showing the upper-level wind direction. Based on the 200 mb wind barbs, blue-dashed lines are locations of upper troughs, blue-zig-zag lines are locations of upper ridges. Blue Ls are locations of upper lows, blue Hs are locations of upper ridges.

In red is surface analysis, with solid lines indicating locations of surface fronts, dashed lines indicating locations of surface troughs, and zig-zag lines indicating surface ridge axes. Ls indicate surface lows, Hs indicate surface highs.

...THERMODYNAMICS BIRDSEYE CHART...

This chart is generated using GOES water vapor satellite imagery. Brown indicates dry air. White, blue, and purple indicates moist air. An increase in moisture indicates slower air parcel lapse rates with elevation and hence an increase toward instability.

Sea-surface temperatures are overlaid with light blue isotherms. The 26 deg C isotherm is highlighted in red. Waters at and south of the 26 deg C isotherm indicate low-level warmth and hence faster environmental lapse rates with elevation (more instability). Waters north of the 26 deg C isotherm indicate slower environmental lapse rates with elevation (less instability).

...MID-LATITUDES DISCUSSION...
P1...Survace frontal system and its upper trough over the central US and central Canada are merging with upper trough and frontal system in paragragph P2. Lowest surface pressure of this system...supported by eastern divergence of this upper trough...has risen from 999 mb to 1002 mb while traveling from the Great Lakes to New York state. Upper convergence behind this upper trough supports a 1020 mb surface ridge near NE Montana. Low-level westerly warm air advection south of this system has spread the SE US upper ridge into the west Alantic. This upper ridge is split into two cells (one over the W Atlantic...the other over the NW Gulf of Mexico) thanks to Caribbean upper vorticity mentioned in paragraph P8.

P2...Surface frontal system and upper trough over eastern Canada persists. 996 mb frontal cyclone south of Newfoundland...supported by eastern divergence of the upper trough...has slightly weakened to 997 mb while traveling northward across E Newfoundland. Cool air advection behind this cyclone has amplified the upper trough into the NW Atlantic. This cyclone has also driven its front southward such that its tail end is E of Bermuda...where a new 1015 mb depression appears to have formed from split flow upper divergence at the boundary between the upper trough mentioned in this paragraph and upper ridge mentioned in paragraph P1. However...upper convergence east of this upper ridge may cause this surface frontal depression to dissipate. On the other hand...if the upper ridge continues spreading eastward...it could overspread the frontal depression and enhance its upper outflow similar to a tropical system. But dry air beneath this upper ridge seen in the above thermo chart would inhibit tropical development.

P3...Surface frontal cyclone near the NE coast of Hudson Bay continues at 997 mb. It is still located beneath the axis of the upper trough mentioned in paragraph P2.

P4...Upper trough is still east of Greenland...and the system's trailing surface front had fizzled. The western end of the trailing front became absorbed into the east side of the systems mentioned in paragraphs P2 and P3. What was left of the eastern end of this trailing front was associated with a surface depression tracking south from the Azores...but that depression had dissipated thanks to upper convergence E of the North Atlantic upper ridge. The North Atlantic upper ridge remains amplified thanks to low-level warm air advection ahead of the systems in paragraphs P2 and P3. As this North Atlantic upper ridge stays amplified...so has the upper trough east of Greenland such that its south end still reaches the NW coast of Africa. Divergence east of this upper trough supports surface troughing over Spain...which has matured into a surface low and front over Spain and NW Africa.

P5...Cut-off upper vorticity south of Bermuda has pushed into the central Caribbean Sea from Hispaniola while retrograding around the upper ridge mentioned in paragraph P1.

P6...Atlantic surface ridge of 1017 to greater-than-1024 mb centers is supported by a few upper convergent sources while stretching from the Gulf of Mexico to the waters offshore of west Europe....including convergence SE of the two upper ridge cells mentioned in paragraph P1...and convergence east of North Atlantic upper ridge (paragraph P4). In conjunction with the south side of the upper ridge in paragraph P8...south side of this surface ridge is helping to waft Africa desert dry air westward across the Atlantic tropics.

...TROPICAL BELT DISCUSSION...
P7...Inverted upper trough over Texas did not fully merge with the upper trough mentioned in paragraph P1. What is left is a cut-off upper vortex over south Texas.

P8...East Atlantic upper ridge persists. Upper vorticity west of the upper ridge...located in the Caribbean Sea...has retrograded NW about the upper ridge in paragraph P1...and into the SE Gulf of Mexico. In the wake of this upper vorticity...a south-central Caribbean upper ridge is building. However...the south-central Caribbean upper ridge is struggling to link with this east Atlantic upper ridge as upper vorticity in paragraph P5 digs southward. Also...upper vorticity remains embedded in this east Atlantic upper ridge...which has moved southwestward from the Canary Islands while retrograding about the amplified North Atlantic upper ridge in paragraph P4. This upper vorticity is splitting this east Atlantic upper ridge in half such that the upper vorticity has developed an inverted upper trough reflection west of the Cape Verde Islands...the reflection building where the east Atlantic upper ridge is splitting. Finally...inverted upper trough midway between the Cape Verdes and Lesser Antilles in the previous discussion is retrograding westward on south side of this east Atlantic upper ridge...and nearing the Lesser Antilles.

P9...Florida Panhandle surface trough has dissipated.

P10...Tropical wave in the western Caribbean in the previous discussion has moved into SE Mexico and Guatemala. It is largely suppressed by Caribbean upper vorticity mentioned in paragraph P8 that has moved into the SE Gulf of Mexico...although split flow divergence between the south-central Caribbean upper ridge (also mentioned in paragraph P8) and the upper vorticity is helping some of its t-storm activity located over the Gulf of Honduras.

P11...The tropical wave midway between the Cape Verde Islands and Lesser Antilles in the previous discussion is nearing the Lesser Antilles. The tropical wave remains suppressed by dry air mentioned in paragraph P6...and by inverted upper trough nearing the Lesser Antilles mentioned toward the end of paragraph P8.

P12...Tropical wave SW of the Cape Verde Islands in the previous discussion is now west of those islands. Although satellite animations still shows a surface low pressure spin...NHC TAFB in last 24 hrs has stopped analyzing this tropical wave as a tropical surface low. As expected during the previous discussion...tropical development has been stopped by dry air ingestion (source of dry air mentioned in paragraph P6). It was also speculated that SW-retrograding upper vorticity from Canary Islands (paragraph P8) would become vertically stacked with this tropical wave and suppress its upper outflow. This process has begun...with the development of an inverted upper trough reflection west of the Cape Verde Islands and over this tropical wave described in more detail in paragraph P8.

P13...Based on satellite imagery...the next tropical wave to roll off of Africa is entering the picture from the lower-right corner of the above atmo birdseye chart.

Updated: 10:33 AM GMT on July 27, 2012

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2012 Atlantic Hurricane Season Birdseye Discussion #63

By: NCHurricane2009, 7:14 AM GMT on July 26, 2012

...JULY 26 2012...3:15 AM EDT...
Atlantic tropics are quiet as strong eastern Atlantic tropical wave will soon encounter unfavorable conditions (see paragraph P12).

...ATMOSPHERIC FEATURES BIRDSEYE CHART...

This chart is generated based on surface analysis from the National Hurricane Center TAFB at 0000Z, and the 0129Z-released HPC analysis.

In light blue is upper air analysis, with 200 mb wind barbs calculated by GOES satellite imagery showing the upper-level wind direction. Based on the 200 mb wind barbs, blue-dashed lines are locations of upper troughs, blue-zig-zag lines are locations of upper ridges. Blue Ls are locations of upper lows, blue Hs are locations of upper ridges.

In red is surface analysis, with solid lines indicating locations of surface fronts, dashed lines indicating locations of surface troughs, and zig-zag lines indicating surface ridge axes. Ls indicate surface lows, Hs indicate surface highs.

...THERMODYNAMICS BIRDSEYE CHART...

This chart is generated using GOES water vapor satellite imagery. Brown indicates dry air. White, blue, and purple indicates moist air. An increase in moisture indicates slower air parcel lapse rates with elevation and hence an increase toward instability.

Sea-surface temperatures are overlaid with light blue isotherms. The 26 deg C isotherm is highlighted in red. Waters at and south of the 26 deg C isotherm indicate low-level warmth and hence faster environmental lapse rates with elevation (more instability). Waters north of the 26 deg C isotherm indicate slower environmental lapse rates with elevation (less instability).

...MID-LATITUDES DISCUSSION...
P1...Next surface frontal and its upper trough arriving from the NW US and SW Canada are pushing into the central US and central Canada this early morning. Its upper trough is merging with Texas upper trough mentioned in paragraph P7. Divergence east of this upper trough supports a broad 999 mb depression along this front. Low-level warm air advection ahead of this system is supporting SE US upper ridge mentioned in paragraph P4.

P2...Surface frontal system and upper trough over eastern Canada persists. After losing its first frontal cyclone to the dominating one in paragraph P3....it has re-established a new 996 mb frontal cyclone south of Newfoundland with the support of eastern divergence of the upper trough. Upper convergence on the back side of this upper trough supports a surface 1015 mb ridge that has moved from Michigan to the coast of NC in the past 24 hours.

P3...Surface frontal cyclone near the NE coast of Hudson Bay has weakened from 990 to 997 mb in the past 24 hours...thanks to the less divergent axis of the upper trough in paragraph P2 moving directly overhead of it. Cold front swinging SE on the back side of this 997 mb frontal cyclone has arrived from Hudson Bay into SE Canada.

P4...Upper trough is still east of Greenland...and the system's trailing front is strewn across the north Atlantic. Upper ridge over the central US behind this system has moved into the SE US while becoming associated with the warm air advection ahead of the system in paragraph P1...and hence this upper ridge is moved to that paragraph. The western end of the trailing front...including frontal depression Invest 98-L and its supporting NW Atlantic upper trough...are becoming absorbed into the east sides of the systems in paragraphs P2 and P3. The North Atlantic upper ridge has greatly amplified thanks to low-level warm air advection ahead of Invest 98-L...and ahead of the systems in paragraphs P2 and P3. As this North Atlantic upper ridge amplifies...so has the upper trough east of Greenland such that its south end now reaches the NW coast of Africa. Divergence east of this upper trough supports surface troughing over Spain. There remains another surface frontal depression over the Azores once supported by this upper trough. As the north Atlantic upper ridge amplifies...eastern convergence of the upper ridge will intensify the surface ridge in paragraph P6 to the west...and this surface ridge will hence steer the Azores surface depression southward. Expect no tropical development of this south-tracking Azores frontal depression as it is in highly unfavorable upper convergence east of the north Atlantic upper ridge...and as it tracks into the dry air mentioned in paragraph P6.

P5...Cut-off upper vorticity south of Bermuda persists...and now extends toward Hispaniola (Haiti and the Dominican Republic).

P6...Atlantic surface ridge of 1018 to greater-than-1024 mb centers is supported by a few upper convergent sources while stretching from the Gulf of Mexico to the waters offshore of west Europe....including convergence southeast of the SE US upper ridge (paragraphs P1 and P4)...and convergence east of North Atlantic upper ridge (paragraph P4). In conjunction with the south side of the upper ridge in paragraph P8...south side of this surface ridge is helping to waft Africa desert dry air westward across the Atlantic tropics.

...TROPICAL BELT DISCUSSION...
P7...Inverted upper trough over Texas is no longer inverted as it merges with mid-latitude upper trough mentioned in paragraph P1.

P8...East Atlantic upper ridge persists. Weakening upper vorticity is still west of the upper ridge...located in the Caribbean Sea. As this upper vorticity weakens...a south-central Caribbean upper ridge is building in its wake that could soon merge with the west end of this east Atlantic upper ridge. Also...upper vorticity remains embedded in this east Atlantic upper ridge...which has moved southwestward from the Canary Islands while retrograding about the amplifying North Atlantic upper ridge in paragraph P4. Inverted upper trough midway between the Cape Verdes and Lesser Antilles in the previous discussion is also retrograding westward.

P9...Florida Panhandle surface trough persists...stalled between the NW end of the surface ridge in paragraph P6 and SW end of the 1015 mb ridge mentioned in paragraph P2.

P10...Tropical waves in the western and central Caribbean in the previous discussion appear to have merged into a single tropical wave per latest NHC TAFB surface maps. It is largely suppressed by Caribbean upper vorticity mentioned in paragraph P8...although split flow divergence between the south-central Caribbean upper ridge (also mentioned in paragraph P8) and Caribbean upper vorticity is helping some of its t-storm activity.

P11...The tropical wave midway between the Cape Verde Islands and Lesser Antilles remains supressed by dry air mentioned in paragraph P6...and by upper convergece east of the inverted upper trough mentioned in paragraph P8.

P12...Tropical wave SE of the Cape Verde Islands in the previous discussion is now centered just SW of the islands with a well-organized 1012 mb surface low pressure spin. Latent heat release of the t-storms continues to inflate a portion of the east Atlantic upper ridge (paragraph P8) such that it is developing a fair upper outflow structure in this upper ridge. It may also get enhanced NW upper outflow from the upper vorticity retrograding SW from the Canary Islands (also see paragraph P8). Despite all this...tropical cyclone formation will soon be inhibited by dry air ingestion (source of dry air mentioned in paragraph P6)...which appears to be starting on the NW half of this tropical wave judging by above thermo chart. Tropical development also looks to be inhibited as the SW-retrograding upper vorticity is on track to become eventually vertically stacked with this tropical wave...in which case the upper vorticity would suppress upper outflow of the tropical wave.

Updated: 10:17 AM GMT on July 27, 2012

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2012 Atlantic Hurricane Season Birdseye Discussion #62

By: NCHurricane2009, 12:25 PM GMT on July 25, 2012

...JULY 25 2012...8:20 AM EDT...
I still expect no tropical cyclone formation from the frontal boundary low northeast of Bermuda and SE of Newfoundland (see paragraph P4 for details). Watching vigorous tropical wave in eastern tropical Atlantic (see paragraph P14 for details).

...ATMOSPHERIC FEATURES BIRDSEYE CHART...

This chart is generated based on surface analysis from the National Hurricane Center TAFB at 0600Z, and the 0741Z-released HPC analysis.

In light blue is upper air analysis, with 200 mb wind barbs calculated by GOES satellite imagery showing the upper-level wind direction. Based on the 200 mb wind barbs, blue-dashed lines are locations of upper troughs, blue-zig-zag lines are locations of upper ridges. Blue Ls are locations of upper lows, blue Hs are locations of upper ridges.

In red is surface analysis, with solid lines indicating locations of surface fronts, dashed lines indicating locations of surface troughs, and zig-zag lines indicating surface ridge axes. Ls indicate surface lows, Hs indicate surface highs.

...THERMODYNAMICS BIRDSEYE CHART...

This chart is generated using GOES water vapor satellite imagery. Brown indicates dry air. White, blue, and purple indicates moist air. An increase in moisture indicates slower air parcel lapse rates with elevation and hence an increase toward instability.

Sea-surface temperatures are overlaid with light blue isotherms. The 26 deg C isotherm is highlighted in red. Waters at and south of the 26 deg C isotherm indicate low-level warmth and hence faster environmental lapse rates with elevation (more instability). Waters north of the 26 deg C isotherm indicate slower environmental lapse rates with elevation (less instability).

...MID-LATITUDES DISCUSSION...
P1...Next surface frontal system in mid-latitude westerlies...and its supporting upper trough...are entering the picture from the NW US and SW Canada.

P2...Surface frontal system and upper trough over Hudson Bay in the previous discussion is now in eastern Canada. The associated 998 mb cyclone has been absorbed into the frontal cyclone discussed in paragraph P3. Upper convergence on the back side of this upper trough supports a surface 1015 mb ridge over Michigan.

P3...Surface frontal cyclone on the NE coast of Hudson Bay has shifted eastward and has intensified to 990 mb. Its intensfication is due to eastern divergence of the upper trough discussed in paragraph P2...and this cyclone has absorbed the frontal cyclone of the system in paragraph P2. Another surface frontal system is swinging SE across Hudson Bay on the back side of this 990 mb cyclone.

P4...While strong surface cyclone east of Greenland has left the picture...its upper trough is still east of Greenland...and its trailing front is strewn across the north Atlantic. Upper ridge over the central US behind this system persists. Along the trailing front...eastern divergence of a NW Atlantic upper trough was intensifying a frontal depression located NE of Bermuda...and in turn cool air advection behind the depression amplified the NW Atlantic upper trough...and warm air advection ahead of the depression amplfied the north Atlantic upper ridge to its east. As expected...the depression has accelerated NE toward cooler waters below 26 deg C while steered ahead of large-scale 990 mb cyclone mentioned in paragraph P3. Before hitting these cooler waters...this depression almost became a tropical cyclone with an increase in t-storms and loss in frontal air mass contrasts...and hence was upgraded to Invest 98-L. In addition to 98-L...there is another surface frontal depression over the Azores once supported by the upper trough E of Greenland. As the north Atlantic upper ridge amplifies...eastern convergence of the upper ridge will intensify the surface ridge in paragraph P6 to the SW...and this surface ridge will hence steer the Azores surface depression southeastward.

P5...Cut-off upper vorticity south of Bermuda persists...but is merging with NW Atlantic upper trough supporting Invest 98-L in paragraph P4.

P6...Atlantic surface ridge of 1019 to 1022 mb centers is supported by a few upper convergent sources while stretching from the Gulf of Mexico all the way toward western Europe....including convergence southeast of the central US upper ridge (paragraph P4)...convergence behind the Bermuda area upper vorticity in paragraph P5...and convergence SE of North Atlantic upper ridge (paragraph P4). In conjunction with the south side of the upper ridge in paragraph P9...south side of this surface ridge is helping to waft Africa desert dry air westward across the Atlantic tropics.

...TROPICAL BELT DISCUSSION...
P7...Upper ridge over Central America has dissipated as the Caribbean upper vorticity in paragraph P9 has retrograded westward about the central US upper ridge in paragraph P4. The westward displacement of this upper vorticity de-amplified the Central America upper ridge.

P8...Inverted upper trough in the Gulf of Mexico has retrograded westward into Texas and the SW US...about the central US upper ridge in paragraph P4.

P9...East Atlantic upper ridge persists. Upper vorticity is still west of the upper ridge...located in the Caribbean Sea. This Caribbean upper vorticity is gradually collapsing (as all cut-off upper vorticity features do)...and as a result a small upper ridge is building in its wake in the south-central Caribbean. Also...upper vorticity remains embedded in this east Atlantic upper ridge...currently positioned over the Canary Islands and waters west. Upper vorticity has also increased in this east Atlantic upper ridge with the formation of an inverted upper trough midway between the Cape Verdes and Lesser Antilles. This inverted upper trough is due to latent-heat-release-driven inflation of the upper ridge segment toward the coast of Africa...caused by vigorous tropical wave in paragraph P14. Finally...Warm air advection ahead of the frontal system mentioned in paragraph P4 extends this upper ridge into western Europe.

P10...Weak surface low in the NE Gulf of Mexico has made landfall on the Florida Panhandle and weakened to a surface trough as expected...as it gets steered by west side of surface ridge in paragraph P6. Its supportive divergent upper ridge...formerly created by its t-storms...has merged with the central US upper ridge in paragraph P4. The tropical wave from which this disturbance stemmed from appears to have left behind yet another surface trough in the W Bay of Campeche...which was added to 0600Z NHC TAFB analysis this morning.

P11...Tropical wave in the central Caribbean in the previous discussion is now located in the western Caribbean. It is suppressed by Caribbean upper vorticity mentioned in paragraph P9.

P12..Tropical wave in the southeast Caribbean in the previous discussion is now crossing the central Caribbean. It is suppressed by Caribbean upper vorticity mentioned in paragraph P9.

P13...The tropical wave west of the Cape Verde Islands in the previous discussion is now midway between the Cape Verdes and Lesser Antilles. The above thermo birdseye chart continues to suggest dry air ingestion is suppressing this tropical wave. The new inverted upper trough mentioned in paragraph P9 is also suppressing this tropical wave.

P14...Tropical wave rolling off of Africa in the previous discussion is now the most impressive of the season so far...featuring a well-organized and stormy 1010 mb low pressure spin SE of the Cape Verde Islands. Latent heat release of the t-storms has inflated a portion of the east Atlantic upper ridge (see paragraph P9) such that it is developing a fair upper outflow structure in this upper ridge. Moreover...the above thermo chart suggests its moisture is pushing out some of the dry air mentioned in paragraph P6..which has plauged the last several tropical waves. Despite all this...computer models runs this morning (specifically GFS and ECMWF) merely propagate this tropical wave as an inverted surface trough in their surface pressure animations. Perhaps the computer models pick up on the dry air in paragraph P6 preventing tropical cyclone development. However...if the moisture field of this tropical wave continues pushing out dry air...we will have to take the threat of tropical cyclone formation from this feature more seriously.

Updated: 3:27 AM GMT on July 26, 2012

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2012 Atlantic Hurricane Season Birdseye Discussion #61

By: NCHurricane2009, 8:11 AM GMT on July 24, 2012

...JULY 24 2012...4:20 AM EDT...
Pop-up tropical disturbance over Florida has diminished (see paragraph P9). Frontal boundary low east-northeast of Bermuda has been introduced into the National Hurricane Center Tropical Weather Outlook...but I expect no tropical cyclone formation from this system (see paragraph P3 for details).

...ATMOSPHERIC FEATURES BIRDSEYE CHART...

This chart is generated based on surface analysis from the National Hurricane Center TAFB at 0000Z, and the 0128Z-released HPC analysis.

In light blue is upper air analysis, with 200 mb wind barbs calculated by GOES satellite imagery showing the upper-level wind direction. Based on the 200 mb wind barbs, blue-dashed lines are locations of upper troughs, blue-zig-zag lines are locations of upper ridges. Blue Ls are locations of upper lows, blue Hs are locations of upper ridges.

In red is surface analysis, with solid lines indicating locations of surface fronts, dashed lines indicating locations of surface troughs, and zig-zag lines indicating surface ridge axes. Ls indicate surface lows, Hs indicate surface highs.

...THERMODYNAMICS BIRDSEYE CHART...

This chart is generated using GOES water vapor satellite imagery. Brown indicates dry air. White, blue, and purple indicates moist air. An increase in moisture indicates slower air parcel lapse rates with elevation and hence an increase toward instability.

Sea-surface temperatures are overlaid with light blue isotherms. The 26 deg C isotherm is highlighted in red. Waters at and south of the 26 deg C isotherm indicate low-level warmth and hence faster environmental lapse rates with elevation (more instability). Waters north of the 26 deg C isotherm indicate slower environmental lapse rates with elevation (less instability).

...MID-LATITUDES DISCUSSION...
P1...Surface frontal system and its supporting upper trough from SW Canada and the NW US in the previous discussion is now over Hudson Bay pushing quickly into eastern Canada. The associated 1004 mb surface frontal cyclone has intensified in the eastern divergence of the upper trough to 998 mb while now located in SE Canada. Upper convergence on the back side of this upper trough supports a surface 1016 mb ridge over Manitoba.

P2...Surface frontal system and its supporting upper trough over eastern Canada in the previous discussion has undergone complex changes in the last 24 hours. Its surface cyclone is now 997 mb on the NE coast of Hudson Bay while now becoming supported by the divergence east of the upper trough in paragraph P1. Meanwhile...its original upper trough has merged with the Ohio Valley upper trough in paragraph P3.

P3...Strong surface frontal cyclone southeast of Greenland has moved northeast out of the picture. Associated upper trough is still east of Greenland. Upper convergence behind this upper trough supports a 1018 mb ridge offshore of Nova Scotia. Upper anticyclone over the central US persists behind this system. Cold front trailing from the strong frontal cyclone has lost its frontal depression offshore of NC while the Ohio Valley upper trough has merged with the upper trough in paragraph P2. This merged upper trough is now in the NW Atlantic...with eastern divergence from this merger intensifying a 1015 mb frontal depression ENE of Bermuda that has been introduced into the National Hurricane Center Tropical Weather Outlook due to t-storm bands developing in its western semicircle. North Atlantic upper ridge in paragraph P7 is also just east of this frontal depression...which provides a means for this frontal depression to have tropical-like upper outflow in its eastern semicircle. Based on computer model runs...expect the NW Atlantic upper trough to merge with upper trough in paragraph P1...and all this upper troughing is going to significantly amplify due to cool air advection on the back side of this intensifying frontal depression. Warm air advection ahead of this same depression will significantly amplify the North Atlantic upper ridge...and eastern convergence of the amplifying upper ridge will intensify the surface ridge in paragraph P5. As the surface ridge intensifies to its east and upper troughing amplifies to the NW...this will coax the frontal depression into a rapid acceleration to the NE and quickly toward waters well below 26 deg C...which is why I do not expect tropical cyclone formation from this frontal depression. Even if cold de-stabilizing temps of upper troughing arrive over the frontal depression...I do not see enough time for transition into a tropical system in waters in the low 20s of deg C...as the depression will have little time over those water temps. I will write a special update later today if this situation changes.

P4...Cut-off upper vorticity south of Bermuda persists...wedged between the North Atlantic upper ridge (paragraphs P7 and P3)...east Atlantic upper ridge in paragraph P8....and warm core upper ridge over the Florida disturbance in paragraph P9. While this upper vorticity is enhancing the southern outflow of the special frontal depression in paragraph P3...still not expecting the frontal depression to become a tropical cyclone for reasons stated in paragraph P3.

P5...Atlantic surface ridge of 1020 to 1024 mb centers is supported by a few upper convergent sources while stretching from the SE US all the way toward western Europe....including convergence southeast of the central US upper anticyclone (paragraph P3)...convergence behind the Bermuda area upper vorticity in paragraph P4...and convergence SE of North Atlantic upper ridge (paragraphs P7 and P3). The west extent of this surface ridge has eroded some in the last 24 hours due to the frontal systems in paragraphs P2 and P3. In conjunction with the south side of the upper ridge in paragraph P8...south side of this surface ridge is helping to waft Africa desert dry air westward across the Atlantic tropics.

...TROPICAL BELT DISCUSSION...
P6...Upper ridge over Central America has re-amplified as the Caribbean upper vorticity mentioned in paragraph P8 weakens. Divergence from this upper ridge has enhanced t-storm activity over Central America.

P7...Inverted upper trough in the southern Gulf of Mexico remains amplified due to sharp definitions of warm core upper ridge of Florida disturbance to its east and central US upper anticyclone (paragraph P3) to its NW. Bermuda-area upper ridge has been spread eastward into the north Atlantic thanks to westerly warm air advection south of the frontal system in paragraph P3....and this North Atlantic upper ridge has been moved to the mid-latitudes discussion in that paragraph.

P8...East Atlantic upper ridge persists. Upper vorticity is still west of the upper ridge...located in the Caribbean Sea. Upper vorticity remains embedded in this upper ridge...originating over Canary Islands days ago and now over the Azores and waters SW. Warm air advection ahead of the strong frontal cyclone mentioned in paragraph P3 extends this upper ridge into western Europe.

P9...Surface tropical wave fragment over Florida has tracked NW into the NE Gulf of Mexico as expected...thanks to the slight western erosion of of the surface ridge described in paragraph P5. Under the outflow of the warm core upper ridge generated by its t-storms yesterday...the tropical wave fragment intensified into a weak 1018 mb surface low. Afterwards...it seems the 1018 mb low advected in the air properties to its west...including the increased upper vorticity of the inverted upper trough mentioned in paragraph P7. As the upper vorticity increased over the surface low...upper outflow directly above it shut off...which is why this disturbance has failed to develop into a tropical cyclone. Meanwhile...the east side of the surface low was able to produce a round of t-storms over the Florida peninsula and SW Atlantic waters while supported by the outflow of the warm core upper ridge. The surface low will continue to round the west side of the paragraph P5 surface ridge...so expect it to continue north into the SE US from the Florida Panhandle.

P10...Tropical wave in the eastern Caribbean Sea in the previous discussion is moving into the central Caribbean. Its t-storm activity is limited by the fact it is still below non-divergent uniform easterly flow...on the south side of the warm core upper ridge in paragraph P9 and north side of Caribbean upper vorticity mentioned in paragraph P8. However...there is an area of directional upper divergence west of Jamaica between the upper vorticity and upper ridge that may allow this tropical wave to see an increase in t-storms in the next 24 hours. It will then potentially enhance pre-existing t-storm activity over Central America mentioned in paragraph P6.

P11..A surprise in the southeast Caribbean and southern Lesser Antilles...as a well-organized cluster of cyclonically turning t-storms developed in the last 24 hours...associated with a tropical wave that had been poorly defined earlier. The intensification of this surface tropical wave is due to enhance poleward upper outflow on the west flank of the upper ridge in paragraph P8....but the t-storms have now rapidly decreased as it heads into an environment of less upper divergence...the same environment that is currently capping the amount of t-storms for the tropical wave in paragraph P10 above. Looking back in time...I estimate this tropical wave emerged from Africa shortly after July 18...based on an extensive area of debris clouds that was observed east of the tropical wave in paragraph P10 from July 19 to 20.

P12...The tropical wave west of the Cape Verde Islands has lost its low pressure spin on NHC TAFB maps in the last 24 hours. The above thermo birdseye chart continues to suggest dry air ingestion into the tropical wave's north half...the source of this dry air mentioned in paragraph P5. Still watching to see if tropical wave will move directly beneath the axis upper ridge in paragraph P8...which would enhance its upper outflow like it did for the tropical wave described in paragraph P11.

P13...A respectable tropical wave is rolling off the coast of Africa this early morning...feature a large mass of t-storms and cyclonic turning. Unlike the previous tropical waves...the surface pressure animations in computer models define this tropical wave better as it propagates westward. However...I am skeptical of tropical cyclone development from this wave too...as the recent string of tropical waves have failed to develop due to dry air currently mentioned in paragraph P5.

Updated: 8:13 AM GMT on July 24, 2012

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2012 Atlantic Hurricane Season Birdseye Discussion #60

By: NCHurricane2009, 4:26 AM GMT on July 23, 2012

...JULY 23 2012...12:30 AM EDT...
Tropical wave that recently emerged from Africa no longer can develop in the short-term due to dry air ingestion (see paragraph P11). Disturbed weather in northern Gulf of Mexico...near Louisiana and Mississippi...has dissipated (paragraph P7).

A pop-up and strong tropical disturbance with tropical cyclone formation potential has developed over the western Bahamas and Florida. See special feature section for further details.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...

This chart is generated based on surface analysis from the National Hurricane Center TAFB at 1800Z, and the 1925Z-released HPC analysis.

In light blue is upper air analysis, with 200 mb wind barbs calculated by GOES satellite imagery showing the upper-level wind direction. Based on the 200 mb wind barbs, blue-dashed lines are locations of upper troughs, blue-zig-zag lines are locations of upper ridges. Blue Ls are locations of upper lows, blue Hs are locations of upper ridges.

In red is surface analysis, with solid lines indicating locations of surface fronts, dashed lines indicating locations of surface troughs, and zig-zag lines indicating surface ridge axes. Ls indicate surface lows, Hs indicate surface highs.

...THERMODYNAMICS BIRDSEYE CHART...

This chart is generated using GOES water vapor satellite imagery. Brown indicates dry air. White, blue, and purple indicates moist air. An increase in moisture indicates slower air parcel lapse rates with elevation and hence an increase toward instability.

Sea-surface temperatures are overlaid with light blue isotherms. The 26 deg C isotherm is highlighted in red. Waters at and south of the 26 deg C isotherm indicate low-level warmth and hence faster environmental lapse rates with elevation (more instability). Waters north of the 26 deg C isotherm indicate slower environmental lapse rates with elevation (less instability).

...SPECIAL FEATURE...TROPICAL WAVE DISTURBANCE...
A strong tropical disturbance over the west Bahamas and Florida...associated with the northern fracture of the tropical wave in paragraph P9...has rapidly developed during the last 24 hours. Special update #59A mentioned that the north fracture of the tropical wave found a very favorable upper divergence regime between the Caribbean upper vorticity (paragraph P8) and SW lobe of the east Atlantic upper ridge (also in paragraph P8). Special update #59B mentioned that the latent heat release of the t-storms has allowed the disturbance to develop a warm core upper anticyclonic ridge for good upper outflow. Therefore...the only unfavorable factor for development is high surface pressures associated with the surface ridge in paragraph P5. Miami obs reported 1021 mb at update #59A...down to 1019 mb at update #59B...and now back up to 1020 mb as of this writing. Key West has reported a 1018 mb pressure slowly rising to 1019 mb from update #59A to now. Mid-level pressure drops have been much more pronounced with the CIMSS 850 mb vorticity product locking on to an increase in the disturabance's mid-level vorticity...and a mid-level low pressure spin evident on satellite/radar over the south tip of Florida moving NW into the Gulf of Mexico. With a recent decrease in t-storm activity and the pressure drops only in the mid-levels...chances have just decreased (but not yet disappeared) for tropical cyclone formation...so this maybe the first and last time this disturbance gets a special feature section on this blog.

Paragraph P5 in the tropical belt discussion mentions erosion of the west end of the Atlantic surface ridge...which is why this disturbance is expected to continue NW into the NE Gulf of Mexico. This ridge erosion may allow for surface pressure drops needed for tropical cyclone formation. Regardless of development or not...gusty winds...heavy rains...and t-storms have already been reported across the west Bahamas and Florida...and the graphic in special update #59B shows the expected track of this weather thru Tuesday July 24 based on the forecast NW track.

...MID-LATITUDES DISCUSSION...
P1...Next surface frontal system and its supporting upper trough in the mid-latitudes has pushed in from SW Canada and the NW US. It has a 1004 mb surface frontal cyclone over Manitoba marked in the above atmo birdseye chart.

P2...Surface frontal system and its supporting upper trough over central Canada has pushed into eastern Canada. Upper convergence on the west side of the upper trough supports a 1018 mb ridge over the Great Lakes. Upper divergence on the east side of the upper trough supports a pre-frontal surface trough over Newfoundland marked in the 1925Z HPC analysis. Warm air advection ahead of this frontal system supports an upper ridge moving into the Atlantic high seas toward Greenland.

P3...Strong deep-layered 966 mb frontal cyclone southeast of Greenland has moved northeast while weakening beneath its less divergent parent upper vortex. The parent upper vortex has weakened into an upper trough east of Greenland. Upper convergence behind this upper trough supports a 1022 mb ridge offshore of Nova Scotia. Upper anticyclone over the central US persists behind this system. Cold front trailing from the 966 mb cyclone has a frontal depression that has moved offshore from North Carolina while its supporting upper trough is still over the Ohio Valley. Convergence on the back side of the Ohio Valley upper trough supports a 1023 mb ridge over West Virginia. There are also a few North Atlantic frontal depressions along this trailing front...supported by divergence between northerlies flowing around the Bermuda-area upper ridge (paragraph P7) and westerlies flowing into upper trough east of Greenland.

P4...Cut-off upper vorticity south of Bermuda persists...wedged between the Bermuda-area upper ridge in paragraph P7...east Atlantic upper ridge in paragraph P8....and newly-formed warm core upper ridge over the disturbance in the special feature section.

P5...Atlantic surface ridge of 1020 to 1026 mb centers is supported by a few upper convergent sources while strecthing from the SW US all the way toward western Europe....including convergence south of the central US upper anticyclone (paragraph P3)...convergence behind the Bermuda area upper vorticity in paragraph P4...and convergence SE of Bermuda-area upper ridge which is being spread eastward into the north Atlantic (paragraph P7). The west extent of this surface ridge may become eroded by the tailings of the frontal systems in paragraphs P1...P2...and P3...which is why the disturbance in the special feature section should track NW into the NE Gulf of Mexico. In conjunction with the south side of the upper ridge in paragraph P8...south side of this surface ridge is helping to waft Africa desert dry air westward across the Atlantic tropics.

...TROPICAL BELT DISCUSSION...
P6...Upper ridge over Central America remains de-amplified into a strong westerly jet as the Caribbean upper vorticity mentioned in paragraph P8 dominates. This upper ridge has an anticyclonic center in the eastern Pacific whose divergence is enhancing the tropical wave in paragraph P9 as it moves into the eastern Pacific.

P7...Upper vorticity in the southern Gulf of Mexico has transitioned into an amplifying inverted upper trough across the Gulf...trapped between the warm core upper ridge of special feature disturbance to its east and central US upper anticyclone (paragraph P3) to its NW. The inverted upper trough's amplfication is due to the amplification of warm core upper ridge assocaited with the special feature disturbance to its east. Bermuda-area upper ridge has been spread eastward into the north Atlantic thanks to westerly warm air advection south of the frontal system in paragraph P3. Northern Gulf t-storm activity near the MS/LA area has dissipated...and the surface trough of this disturbed weather has merged with a surface trough over the SE US...a breakage of the trailing cold front mentioned in paragraph P3.

P8...East Atlantic upper ridge persists. Upper vorticity is still west of the upper ridge...located across the Caribbean Sea. This east Atlantic upper ridge remains split into three cells thanks to embedded upper vorticity originating from Canary Islands and now partially over the Azores. The northern cell is moving into west Europe while associated with warm air advection ahead of the strong frontal cyclone mentioned in paragraph P3...the SW cell has an anticylonic center just N of the Lesser Antilles...and the SE cell is located toward Africa.

P9...Tropical wave pushing into central America/SE Mexico in the previous discussion has moved into the eastern Pacific...where the anticyclonic center of upper ridge in paragrah P6 is enhancing it. Westerly jet also mentioned in paragraph P6 looks directionally divergent based on the 200 mb wind barbs shown in the above atmo birdseye chart...this divergence supporting persistent t-storms over Central America and east of this tropical wave. Today...it is now apparent the tropical wave left behind a north fracture tracking across the west Bahamas and Florida. This north fracture contributed to a rapidly developing tropical disturbance as described in the above special feature section. See the special feature section for further details.

P10...Tropical wave approaching crossing the Lesser Antilles in the previous discussion is now in the eastern Caribbean Sea. Its t-storm activity is limited by the fact it is still below non-divergent uniform easterly flow on the southwest side of the upper ridge in paragraph P8.

P11...The tropical wave (with t-storms and low pressure spin) over the Cape Verde Islands in the previous discussion is now just west of those islands. Low pressure spin is analyzed at 1014 mb per 1800Z NHC TAFB map. Satellite shows a decrease in t-storm activity across the north half of the tropical wave as it ingests dry air (mentioned in paragraph P5)...so chances for this wave's development have decreased for the short term. However...still watching to see if tropical wave will move directly beneath the SE cell of the upper ridge in paragraph P8. If this were to occurr...the cell directly overhead and upper vorticity to the northwest (also mentioned in paragraph P8) would enhance the upper outflow of this tropical wave.

Updated: 8:44 AM GMT on July 24, 2012

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2012 Atlantic Hurricane Season Birdseye Discussion #59B (Special Update)

By: NCHurricane2009, 8:37 PM GMT on July 22, 2012

...JULY 22 2012...4:37 PM EDT...
See special update #59A concerning how the strong disturbance over Florida and the west Bahamas materialized. This special update is written as tropical cyclone formation opportunity appears to be increasing by the hour...and is written to update the impact forecast based on radar data seen after update #59A.

Concerning tropical cyclone formation opportunity...update #59A stated that this would not occur unless...

(1) The disturbance's latent heat release builds a divergent warm core upper anticyclone that can push out the upper convergence that lies ahead in the Gulf of Mexico

(2) Surface pressures begin falling.

Criteria 1 is met per latest GOES satellite-derived 200 mb wind barbs.

Concerning criteria 2...CIMSS 850 mb (mid-level) vorticity product suggest pressures have dropped at the mid-levels as the vorticity has increased. A mid-level spin is also evident on very recent satellite and radar animation...near the south tip of south Florida. At the very surface...Miami obs have seen pressures drop from 1021 to 1019 mb since update #59A. All current observations show a more NW track (rather than WNW track mentioned in update #59A). When looking at the GFS model's forecast for the next two days...it is not readily apparent what is causing the northward turn as the central US upper anticyclone (paragraph P2...discussion #59) stays in place due north of this disturbance. However for the steering on a shallow tropical disturbance like this...one has to look at the surface rather than upper-levels...and the GFS shows the west end of the Atlantic surface ridge (paragraph P4...discussion #59) eroding due to the tail end of the front in paragraph P2 discussion 59...re-enforced by the tail end of the front in paragraph P1 discussion 59...up thru the first half of Tuesday July 24. This surface ridge erosion may also allow surface pressures to drop...and is what is causing the northward turn. Forecasting a northward turn is also in alignment with the NHC tropical weather outlook written earlier at 2 PM EDT.

Photobucket
Figure 1: Updated radar image and impact forecast for tropical disturbance presently over south Florida and west Bahamas.

With the forecast northward turn...Figure 1 above is an updated radar-based impact forecast for this disturbance. Due to the above two criteria becoming increasingly met...I will be considering this a special feature on my next full discussion...which will probably be released very late this evening or in the hours just after midnight EDT.

Updated: 8:40 PM GMT on July 22, 2012

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2012 Atlantic Hurricane Season Birdseye Discussion #59A (Special Update)

By: NCHurricane2009, 5:38 PM GMT on July 22, 2012

...JULY 22 2012...1:37 PM EDT...
Widely scattered thunderstorms from Jamaica...east Cuba...and the east Bahamas...supported by split flow divergence between the SW lobe of the east Atlantic upper ridge and Caribbean upper vorticity...have tremendously increased over the last 12 hours while moving into the west Bahamas and south Florida. Due to measured gusty winds over south Florida and impressive satellite presentation...the National Hurricane Center (NHC) has given this a 10% chance of developing in the next 48 hours. This activity was previously mentioned in paragraph P7 of full discussion #59. The Caribbean upper vorticity is shown by blue-dashed line in Figure 1...while the blue-zig-zag line shows the SW lobe of the east Atlantic upper ridge.

At the surface...tropical wave mentioned in paragraph P8 of discussion #59 had been previously associated with this t-storm activity...but it is possible that it left behind a surface trough (red-dashed line in Figure 1) that had not been previously analyzed until today. Surface convergence from the surface trough is certainly enhancing this t-storm activity...and expect the surface trough to track WNW into the Gulf of Mexico while steered by the Atlantic surface ridge (paragraph P4...discussion #59 and red-zig-zag line of Figure 1). This steering forecast is certainly supported by looking at the latest CIMSS steering products. Gusty winds observed in south Florida are due to pressure gradient between the surface trough and surface ridge.

With sea-surface temps at 29 to 30 deg C...split flow upper divergence shown in Figure 1...and surface convergence from surface trough...it would seem conditions are very favorable for tropical cyclone formation...and indeed I believe they are in the very short term. However...I am not forecasting tropical cyclone formation for two reasons. Atlantic surface ridge (paragraph P4...discussion #59 and red-zig-zag line of Figure 1) is keeping surface pressures high...for example the latest Miami surface obs shows 1021 mb of pressure. A look at Figure 1 shows this disturbance heading toward unfavorable upper convergence in the Gulf of Mexico...as the northerly flow from central US upper anticyclone (paragraph P2 of discussion #59) converges with easterly flow from the Caribbean upper vorticity (paragraph P7...discussion #59....blue-dashed line in Figure 1).

Until surface pressures start significantly falling over the west Bahamas/south Florida...and until this disturbance's latent heat release builds a divergent warm core upper anticyclone that can push out the upper convergence that lies ahead...I expect no tropical cyclone formation out of this system.


Figure 1: Meteorological analysis of surface and upper winds around the pop-up disturbance over the west Bahamas and south Florida.

Even with no tropical cyclone formation...impacts are already being felt. Using the latest radar animation...my forecast impacts are shown in Figure 2 below.


Figure 2: Radar imagery of pop-up disturbance over the west Bahamas and south Florida.

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2012 Atlantic Hurricane Season Birdseye Discussion #59

By: NCHurricane2009, 1:36 AM GMT on July 22, 2012

...JULY 21 2012...9:40 PM EDT...
Still monitoring the next tropical wave that has emerged from Africa (see paragraph P10). Disturbed weather in northern Gulf of Mexico...near Louisiana and Mississippi...still does not appear to have tropical development potential (paragraph P6).

...ATMOSPHERIC FEATURES BIRDSEYE CHART...

This chart is generated based on surface analysis from the National Hurricane Center TAFB at 1800Z, and the 1922Z-released HPC analysis.

In light blue is upper air analysis, with 200 mb wind barbs calculated by GOES satellite imagery showing the upper-level wind direction. Based on the 200 mb wind barbs, blue-dashed lines are locations of upper troughs, blue-zig-zag lines are locations of upper ridges. Blue Ls are locations of upper lows, blue Hs are locations of upper ridges.

In red is surface analysis, with solid lines indicating locations of surface fronts, dashed lines indicating locations of surface troughs, and zig-zag lines indicating surface ridge axes. Ls indicate surface lows, Hs indicate surface highs.

...THERMODYNAMICS BIRDSEYE CHART...

This chart is generated using GOES water vapor satellite imagery. Brown indicates dry air. White, blue, and purple indicates moist air. An increase in moisture indicates slower air parcel lapse rates with elevation and hence an increase toward instability.

Sea-surface temperatures are overlaid with light blue isotherms. The 26 deg C isotherm is highlighted in red. Waters at and south of the 26 deg C isotherm indicate low-level warmth and hence faster environmental lapse rates with elevation (more instability). Waters north of the 26 deg C isotherm indicate slower environmental lapse rates with elevation (less instability).

...MID-LATITUDES DISCUSSION...
P1...Surface frontal system and its supporting upper trough over central Canada continues pushing east. Upper convergence on the west side of the upper trough supports a 1019 mb ridge near the North Dakota/Minnesota border. Warm air advection ahead of this frontal system has supports an upper ridge over eastern Canada.

P2...Strong frontal cyclone southeast of Greenland has rapidly intensified to 966 mb...thanks to strong upper divergence on the east side of its supporting upper trough moving offshore from E Canada. Cool air advection behind the surface cyclone has amplified the upper trough into an upper vortex directly aligned with the 966 mb center...and now we have a deep-layered vortex SE of Greenland. The 966 mb center should now begin weakening with a much less divergent environment beneath the upper vortex. Upper convergence behind the deep-layered vortex supports a 1026 to 1019 mb ridge over SE Canada. Upper anticyclone over the west US has grown into the central US. Cold front trailing from the 966 mb cyclone has a frontal depression and its supporting upper trough over the Ohio Valley. There are also several NW Atlantic frontal depressions along this trailing front...supported by divergence between northerlies flowing around the Bermuda-area upper ridge (paragraph P6) and westerlies flowing into the 966 mb deep-layered vortex.

P3...Cut-off upper trough south of Bermuda persists...and has an east-west extent while compressed between the Bermuda-area upper ridge in paragraph P6 and east Atlantic upper ridge in paragraph P7.

P4...Open Atlantic surface ridge is supported by a few upper convergent sources this evening. Convergence south of the central US upper anticyclone (paragraph P2) supports 1020 mb centers over the SW US and Gulf of Mexico. Convergence SE of Bermuda-area upper ridge (paragraph P6) supports a 1025 mb center east of Bermuda. Convergence east of the north cell of the upper ridge in paragraph P7 supports a 1026 mb center just south of the Azores. In conjunction with the south side of the upper ridge in paragraph P7...south side of this surface ridge is helping to waft Africa desert dry air westward across the Atlantic tropics.

...TROPICAL BELT DISCUSSION...
P5...Upper ridge over Central America has de-amplified further into a strong westerly jet as the westward-retrograding Caribbean upper vorticity mentioned in paragraph P7 pushes in.

P6...Upper vorticity in the southern Gulf of Mexico is weakening over the Yucatan and SE Mexico....and the SE US upper trough it left behind has been absorbed by the Ohio Valley upper trough mentioned in paragraph P2. Bermuda-area upper ridge persists east of all this upper vorticity...and westerly advection of warm air associated with the upper ridge...ahead of the NW Atlantic frontal depressions in paragraph P2...has spread this upper ridge eastward. T-storm activity continues persisting over the MS/LA area with associated surface trough. Continued latent heat release from the t-storm clouds continues inflating the south lobe of the central US upper anticyclone (paragraph P2) such that the disturbance has upper anticyclonic outflow that is allowing the disturbance to survive. However...land interaction and high surface pressures from the paragraph P4 ridge continue to limit tropical development potential. If at any time this disturbed weather loses aforementioned latent heat release driven upper outflow...it will then quickly succumb to upper convergence on the south side of central US upper anticyclone and dissipate. Just like last night...there is potential for an impulse of this disturbed weather to shift SW into the SE corner of Texas. The surface trough of this disturbance may soon get absorbed into adjacent 1013 mb low...which is a breakage of the trailing cold front discussed in paragraph P2.

P7...East Atlantic upper ridge persists. Upper vorticity is still west of the upper ridge...located across the Caribbean Sea. A NW Caribbean upper vortex from this vorticity is retrograding westward about the SW lobe of this east Atlantic upper ridge. Although the tropical wave in paragraph P8 has moved out of the area...t-storms persist over the Jamaica...east-Cuba...east-Bahamas area thanks to split flow divergence between the SW lobe of this east Atlantic upper ridge and Caribbean upper vorticity. This east Atlantic upper ridge is now split into three cells thanks to embedded upper trough originating from Canary Islands (which is now breaking into a few upper vortices). The northern cell is near west Europe while associated with warm air advection ahead of the 966 mb cyclone in paragraph P2...the SW cell has an anticylonic center just N of the Lesser Antilles...and the SE cell is located toward Africa.

P8...Tropical wave in the central Caribbean Sea in the previous discussion is now in the western Caribbean and pushing into Central America/SE Mexico. It is in a hositle westerly vertical shear environment thanks to jet mentioned in paragraph P5..although the jet looks directionally divergent based on the 200 mb wind barbs shown in the above atmo birdseye chart. This divergence supports t-storm activity over Panama/Costa Rica and 1008 mb surface low in the ITCZ. Normally I do not mark ITCZ features in the above charts...but this time I have in case it is associated with this tropical wave's south end.

P9...Tropical wave approaching the Lesser Antilles in the previous discussion is now crossing those islands into the eastern Caribbean Sea. It has produced some scattered t-storm clouds...but the expanse of its t-storm activity is limited by the fact it is below non-divergent uniform easterly flow on the south side of the upper ridge in paragraph P7.

P10...The tropical wave (with t-storms and low pressure spin) that rolled off of Africa in the previous discussion is now over the Cape Verde Islands. Low pressure spin is analyzed at 1011 mb per 1800Z NHC TAFB map. Satellite shows yet another spin with this tropical wave that just rolled off of Africa...so either this is the far east extent of this tropical wave or perhaps a highly-amplified mid-level AEJ (African Easterly Jet) trough whose western divergence spawned the tropical wave while it was over Africa. Satellite also shows a decrease in t-storm activity in the last 24 hours...so it may seem the dry air (mentioned in paragraph P4) is affecting this tropical wave. However...the above thermo charts shows moisture with this tropical wave is pushing out some of this dry air...so instead the decrease in t-storms may be from recently moving over the relatively cooler (more stable) low-level marine air as opposed to the hotter low-level (and more unstable) air over African land it was recently over. As the GFS model has been predicting...amplified Canary Islands upper trough in paragraph P7 is breaking into SW retrograding upper vortices. The tropical wave could soon move directly beneath the SE cell of the upper ridge in paragraph P7...the cell directly overhead and upper vortices to the northwest enhancing the upper outflow of this tropical wave. It is also still possible that dry air in paragraph P4 stops this tropical wave from developing altogether.

Updated: 1:41 AM GMT on July 22, 2012

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2012 Atlantic Hurricane Season Birdseye Discussion #58

By: NCHurricane2009, 6:05 AM GMT on July 21, 2012

...JULY 21 2012...2:08 AM EDT...
Watching the next tropical wave emerging from Africa (see paragraph P11). Pop-up disturbance in northern Gulf of Mexico...near Louisiana and Mississippi...does not appear to have tropical development potential (paragraph P6).

...ATMOSPHERIC FEATURES BIRDSEYE CHART...

This chart is generated based on surface analysis from the National Hurricane Center TAFB at 1800Z, and the 1934Z-released HPC analysis.

In light blue is upper air analysis, with 200 mb wind barbs calculated by GOES satellite imagery showing the upper-level wind direction. Based on the 200 mb wind barbs, blue-dashed lines are locations of upper troughs, blue-zig-zag lines are locations of upper ridges. Blue Ls are locations of upper lows, blue Hs are locations of upper ridges.

In red is surface analysis, with solid lines indicating locations of surface fronts, dashed lines indicating locations of surface troughs, and zig-zag lines indicating surface ridge axes. Ls indicate surface lows, Hs indicate surface highs.

...THERMODYNAMICS BIRDSEYE CHART...

This chart is generated using GOES water vapor satellite imagery. Brown indicates dry air. White, blue, and purple indicates moist air. An increase in moisture indicates slower air parcel lapse rates with elevation and hence an increase toward instability.

Sea-surface temperatures are overlaid with light blue isotherms. The 26 deg C isotherm is highlighted in red. Waters at and south of the 26 deg C isotherm indicate low-level warmth and hence faster environmental lapse rates with elevation (more instability). Waters north of the 26 deg C isotherm indicate slower environmental lapse rates with elevation (less instability).

...MID-LATITUDES DISCUSSION...
P1...Next surface frontal system and upper trough in mid-latitude westerlies is entering the birdseye charts from the upper-left corner...moving into central Canada. Warm air advection ahead of this frontal system has created an upper ridge over eastern Canada.

P2...Vigorous frontal cyclone south of Greenland is maintained by divergence east of a sharp upper trough pushing offshore from eastern Canada...and is 987 mb as of 1934Z. Upper convergence behind the sharp E Canada upper trough supports a 1022 mb ridge over the Great Lakes and E Canada. Upper anticyclone over the SW US has grown into the western US behind the sharp E Canada upper trough. Cold front trailing from the 987 mb cyclone has a frontal depression and its supporting upper trough embedded...which has traveled from Michigan into the Ohio Valley in the last 24 hours.

P3...Cut-off upper vortex south of Bermuda has weakened into an upper trough in the last 24 hours...compressed between the Bermuda-area upper ridge in paragraph P6 and east Atlantic upper ridge in paragraph P7.

P4...Open Atlantic surface ridge is supported by a few upper convergent sources this early morning. Convergence south of the western US upper anticyclone (paragraph P2) supports 1020 to 1021 mb centers over the SW US and Gulf of Mexico. Convergence SE of Bermuda-area upper ridge (paragraph P6) supports a 1024 mb center east of Bermuda. Convergence behind the Canary Islands upper trough (paragraph P7) supports a 1027 mb center just south of the Azores. In conjunction with the south side of the upper ridge in paragraph P7...south side of this surface ridge is helping to waft Africa desert dry air westward across the Atlantic tropics.

...TROPICAL BELT DISCUSSION...
P5...Upper ridge over the south Caribbean Sea currently covers Central America as a wave. Divergence west of this upper ridge wave supports t-storm activity over Panama and Costa Rica.

P6...Upper vorticity in the southern Gulf of Mexico is weakening over the Yucatan and SE Mexico....and leaves behind upper vortex over the SC/GA border that has recently weakened into a SE US upper trough. Bermuda-area upper ridge persists east of all this upper vorticity. T-storm activity continues to flourish over the MS/LA area with surface trough formation...all supported by split flow divergence at the boundary between the SE US upper trough and west US upper anticyclone (paragraph P2). Latent heat release from the t-storm clouds appears to be inflating the south lobe of the west US upper anticyclone such that the disturbance is developing upper anticyclonic outflow similar to a tropical system. However...land interaction and high surface pressures from the paragraph P4 ridge limit tropical development potential. Expect SE US upper trough to merge with Ohio valley upper trough in paragraph P2...reducing the split flow upper divergence between the SE US upper trough and west US upper anticyclone supporting this weather. Therefore...if this disturbed weather loses aforementioned latent heat release driven upper outflow...it will then quickly succumb to upper convergence on the south side of west US upper anticyclone and dissipate. In the meantime...radar shows rainfall pushing out of MS/LA and toward SE Texas...while S MS and SE LA have flood advisories due to previous rainfall from this system.

P7...East Atlantic upper ridge persists. Upper vorticity is still west of the upper ridge...located in the central Caribbean Sea. This upper ridge remains dwarfed in half by Canary Islands upper trough...the western half amplifying via warm air advection ahead of paragraph P2 frontal system...the east half located toward Africa. Amplification of west half of this upper ridge is causing amplification of the Canary Islands upper trough.

P8...Tropical wave moving across SE Mexico in the previous discussion has moved into the eastern Pacific and outside the scope of the above charts. This is the last statement on this tropical wave on this blog.

P9...Tropical wave in the eastern Caribbean Sea in the previous discussion is pushing into the central Caribbean. Surface convergence east of this tropical wave axis...coupled with split flow upper divergence between the east side of the central Caribbean upper vortex and east Atlantic upper ridge (paragraph P7)...has caused t-storm activity to develop across Puerto Rico...Hispaniola...and Jamaica in the last 24 hours.

P10...Tropical wave midway between the Cape Verde Islands and Lesser Antilles in the previous discussion is approaching the Lesser Antilles. This tropical wave still has an impressive structure with a cyclonic turning of faint clouds still visible on satellite...but its t-storm activity is limited by the fact it is below non-divergent uniform easterly flow on the south side of the upper ridge in paragraph P7. The above thermo birdseye chart suggests the NW half of its cyclonic flow has ingested dry air mentioned in paragraph P4...while the SE half still has moisture.

P11...Satellite imagery suggests an impressive tropical wave (with t-storms and organized low pressure spin) has rolled off of Africa. Dry air (mentioned in paragraph P4) has been a problem for the past several tropical waves...so it is uncertain if this tropical wave will develop despite an impressive structure. GFS computer model shows no development with this tropical wave...but a study of its upper wind forecast suggests potentially favorable conditions for development. Canary Islands upper trough is currently amplifying as described in paragraph P7...and the GFS model breaks off an upper vortex from the amplifying trough that retrogrades westward about the west half of the upper ridge in paragraph P7. If this tropical wave phases properly with the forecast upper vortex...the upper vortex could enhance the northwestern upper outflow of this tropical wave in the coming days. The upper vortex is later forecast to stall while merging with the upper trough in paragraph P1...and also is forecast to leave behind upper vorticity in the Caribbean Sea and ahead of the tropical wave. Therefore...if the tropical wave does not develop east of the Caribbean Sea due to dry air...it will later encounter unfavorable upper winds as it catches up to the stalling upper vorticity.

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2012 Atlantic Hurricane Season Birdseye Discussion #57

By: NCHurricane2009, 7:26 AM GMT on July 20, 2012

...JULY 20 2012...3:35 AM EDT...
Atlantic tropics still quiet. However...watching the next tropical wave about to emerge from Africa (see paragraph P11).

...ATMOSPHERIC FEATURES BIRDSEYE CHART...

This chart is generated based on surface analysis from the National Hurricane Center TAFB at 1800Z, and the 1922Z-released HPC analysis.

In light blue is upper air analysis, with 200 mb wind barbs calculated by GOES satellite imagery showing the upper-level wind direction. Based on the 200 mb wind barbs, blue-dashed lines are locations of upper troughs, blue-zig-zag lines are locations of upper ridges. Blue Ls are locations of upper lows, blue Hs are locations of upper ridges.

In red is surface analysis, with solid lines indicating locations of surface fronts, dashed lines indicating locations of surface troughs, and zig-zag lines indicating surface ridge axes. Ls indicate surface lows, Hs indicate surface highs.

...THERMODYNAMICS BIRDSEYE CHART...

This chart is generated using GOES water vapor satellite imagery. Brown indicates dry air. White, blue, and purple indicates moist air. An increase in moisture indicates slower air parcel lapse rates with elevation and hence an increase toward instability.

Sea-surface temperatures are overlaid with light blue isotherms. The 26 deg C isotherm is highlighted in red. Waters at and south of the 26 deg C isotherm indicate low-level warmth and hence faster environmental lapse rates with elevation (more instability). Waters north of the 26 deg C isotherm indicate slower environmental lapse rates with elevation (less instability).

...MID-LATITUDES DISCUSSION...
P1...Next surface frontal system and upper trough in mid-latitude westerlies is entering the birdseye charts from the upper-left corner of the above birdseye charts...located over western Canada.

P2...In the last 24 hours...995 mb frontal cyclone over Newfoundland has intensified further to 988 mb while entering the Atlantic S of Greenland. Its supporting E Canada upper vortex follows behind....and is now a sharp upper trough whose eastern divergence intensified the surface cyclone. Shortwave upper trough from this system ejecting toward Europe 24 hrs ago is now making landfall in Europe. Upper convergence behind the sharp E Canada upper trough supports a 1022 mb ridge over Hudson Bay. The central US upper anticyclone has been split by the sharp E Canada upper trough...with one anticyclone over the SW US...and another over the SE US. Texas cut-off upper vortex left behind by this system days ago is retrograding westward into N Mexico around the SW US anticyclone. SW US surface ridge once supported by convergence on the back side of the Texas cut-off upper vortex is now supported by convergence SE of the SW US upper anticyclone...and is currently at 1021 mb. Cold front trailing from the 988 mb cyclone has a frontal depression and its supporting upper trough embedded...which has traveled from E Iowa to Michigan in the last 24 hours.

P3...What is left of the Upper trough fragment E of Bermuda is now a cut-off upper vortex just south of Bermuda. The upper trough fragment over the Azores has merged with a Canary Islands upper trough (see paragraph P7 for details on the merger).

P4...Open Atlantic surface ridge is supported by a few upper convergent sources this morning. Convergence SE of the SE US upper anticyclone (paragraph P2) and convergence SE of Bermuda-area upper ridge (paragraph P6) supports the west lobe of this surface ridge extending all the way into the Gulf of Mexico. Convergence behind the Canary Islands upper trough (paragraph P7) supports a 1028 mb center SW of the Azores. In conjunction with the south side of the upper ridge in paragraph P7...south side of this surface ridge is helping to waft Africa desert dry air westward across the Atlantic tropics.

...TROPICAL BELT DISCUSSION...
P5...Upper ridge covering the south Caribbean Sea has re-flourished in the last 24 hours as it recovers real estate in the wake of the weakening upper vorticity in paragraph P6. Its divergent anticyclonic center is supporting increased t-storms over the Panama area.

P6...Upper vorticity in the southern Gulf of Mexico is weakening....but still extends to an upper vortex at the FL/GA border that has recently drifted to the SC/GA border. T-storm activity has flourished over the MS/LA area...supported by split flow divergence at the boundary between the SC/GA upper vortex and SE US upper anticyclone in paragraph P2. Bermuda-area upper ridge persists east of all this upper vorticity...but is weakening as the sharp E Canada upper trough in paragraph P2 pushes in.

P7...East Atlantic upper ridge persists. Upper vorticity is still west of the upper ridge...located in the central Caribbean Sea. The anticyclonic center of this upper ridge has continued drifting westward while becoming associated with warm air advection ahead of the complex frontal system in paragraph P2. The westward migration of this anticyclonic center has split this upper ridge from the upper ridge extending from Africa's desert. In between the two upper ridges...an upper trough formed over the Canary Islands...and the Azores upper trough in paragraph P3 has merged with it. The anticyclonic center of this upper ridge is amplifying from aforementioned warm air advection...which is causing the Canary Islands upper trough to also amplify.

P8...Tropical wave moving across SE Mexico in the previous discussion continues to do so...and is still suppressed by the south Gulf of Mexico upper vorticity discussed in paragraph P6.

P9...Tropical wave approaching the Lesser Antilles in the previous discussion has crossed those islands into the eastern Caribbean Sea. Its t-storm activity expanded thanks to enhanced poleward upper outflow on the west flank of the E Atlantic upper ridge in paragraph P7. Its t-storm activity has recently dwindled...as it heads into a less favorable environment directly below the central Caribbean upper vortex mentioned in paragraph P7.

P10...Tropical wave west of the Cape Verde Islands in the previous discussion is now midway between the Cape Verdes and Lesser Antilles. This tropical wave has an impressive structure with a swirl of clouds still visible on satellite...but its t-storm activity is limited by the fact it is below non-divergent uniform easterly flow on the south side of the upper ridge in paragraph P7. The above thermo birdseye chart suggests moisture associated with the tropical wave continues pushing out some of the dry air mentioned in paragraph P4...although the same chart suggests the north half of its swirl is now ingesting this dry air.

P11...Satellite imagery suggests an impressive tropical wave (with t-storms and low pressure spin) is about to roll off of Africa. Dry air (mentioned in paragraph P4) has been a problem for the past several tropical waves...but this one may be protected by the moisture shield associated with the tropical wave in paragraph P10. GFS computer model shows no development with this tropical wave...but a study of its upper wind forecast suggests potentially favorable conditions for development. A Canary Islands upper trough is currently amplifying to the east of an anticyclonic upper ridge as described in paragraph P7...and the GFS model breaks off an upper vortex from the amplifying trough that retrogrades westward about the upper anticyclone. If this tropical wave phases properly with the forecast upper vortex...the upper vortex could enhance the northern or northwestern upper outflow of this tropical wave in the coming days.

Updated: 7:37 AM GMT on July 20, 2012

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2012 Atlantic Hurricane Season Birdseye Discussion #56

By: NCHurricane2009, 7:34 AM GMT on July 19, 2012

...JULY 19 2012...3:45 AM EDT...
Atlantic tropics still quiet.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...

This chart is generated based on surface analysis from the National Hurricane Center TAFB at 0000Z, and the 0124Z-released HPC analysis.

In light blue is upper air analysis, with 200 mb wind barbs calculated by GOES satellite imagery showing the upper-level wind direction. Based on the 200 mb wind barbs, blue-dashed lines are locations of upper troughs, blue-zig-zag lines are locations of upper ridges. Blue Ls are locations of upper lows, blue Hs are locations of upper ridges.

In red is surface analysis, with solid lines indicating locations of surface fronts, dashed lines indicating locations of surface troughs, and zig-zag lines indicating surface ridge axes. Ls indicate surface lows, Hs indicate surface highs.

...THERMODYNAMICS BIRDSEYE CHART...

This chart is generated using GOES water vapor satellite imagery. Brown indicates dry air. White, blue, and purple indicates moist air. An increase in moisture indicates slower air parcel lapse rates with elevation and hence an increase toward instability.

Sea-surface temperatures are overlaid with light blue isotherms. The 26 deg C isotherm is highlighted in red. Waters at and south of the 26 deg C isotherm indicate low-level warmth and hence faster environmental lapse rates with elevation (more instability). Waters north of the 26 deg C isotherm indicate slower environmental lapse rates with elevation (less instability).

...MID-LATITUDES DISCUSSION...
P1...1003 mb frontal cyclone ejecting east from Hudson Bay has intensified to 995 mb in the last 24 hours...and is now over Newfoundland. Its supporting upper trough amplified into an E Canada upper vortex due to cool air advection behind the intensifying cyclone. The 995 mb cyclone has absorbed the 1006 mb cyclone SW of Greeland in the last 24 hours...but that cyclone's upper trough is ejecting eastward into the system that made landfall in Europe (paragraph P2). Upper convergence behind the E Canada upper vortex supports a 1020 mb ridge SW of Hudson Bay. Cut-off upper vortex over Texas left behind by this system days ago persists...while the central US upper anticyclone also persists. Upper convergence behind the Texas cut-off upper vortex supports a 1016 mb ridge over the SW US. Cold front trailing from what is now the 995 mb Newfoundland cyclone has been on the north side of what is now the central US uppper anticyclone...and since July 15 I have noticed a depression along this front originating from E Montana...which is now 1008 mb over E Iowa. Perhaps the depression originated from accelerational divergence beneath a westerly jet on the north side of the central US upper anticyclone...but now the depression's cool air advection has carved out its own upper trough whose eastern divergence continues supporting this surface depression. Because this supporting upper trough is heading east into the E Canada upper vortex...expect the surface depression to follow suit.

P2...Surface frontal system and associated upper trough has made landfall in Europe...with the convergent back side of this European upper trough supporting a 1020 mb surface ridge SE of Greenland. Upper trough fragment E of Bermuda that originated from this system days ago persists. This upper trough fragment has split into two areas...an inverted upper trough SE of Bermuda...and regular upper trough SE of Newfoundland. The upper trough fragment west of the Azores...also left behind by this system (but only 24 hrs ago)...is now over the Azores.

P3...Open Atlantic surface ridge is supported by a few upper convergent sources this morning. Convergence south of the central US upper anticyclone (paragraph P1) and convergence SE of Bermuda-area upper ridge (paragraph P5) supports the west lobe of this surface ridge extending all the way into the Gulf of Mexico. Convergence behind the Azores upper trough fragment (paragraph P2) and developing upper trough over the Canary Islands (paragraph P6) supports a 1030 mb center SW of the Azores. In conjunction with the south side of the upper ridge in paragraph P6...south side of this surface ridge is helping to waft Africa desert dry air westward across the Atlantic tropics.

...TROPICAL BELT DISCUSSION...
P4...Upper ridge covering the south Caribbean Sea is de-amplifying...becoming squeezed between the E Caribbean upper vorticity in paragraph P6 that is migrating westward toward the upper vorticity in paragraph P5. It appears that accelerational divergence from a westerly jet on the north side of this upper ridge and south side of the upper vorticity in paragraph P5 has been increasing the t-storm activity across SE Mexico and Central America in the last 48 hours.

P5...Upper vorticity in the southern Gulf of Mexico persists...and still extends to another upper vortex at the FL/GA border. Florida surface trough once supported by divergence between the S Gulf vortex and FL/GA vortex has dissipated. Bermuda-area upper ridge perists east of all this upper vorticity.

P6...East Atlantic upper ridge persists. Upper vorticity is still west of the upper ridge...located toward the E Caribbean Sea and migrating westward into the central Caribbean while retrograding about the Bermuda-area upper ridge in paragraph P5. Weakening inverted upper trough (midway between Cape Verdes and Lesser Antilles) on the south side of this upper ridge has dissipated. Meanwhile...the Azores upper trough in paragraph P2 has pushed the anticyclonic center of this upper ridge southwestward...seperating this upper ridge from the African desert upper ridge. In between the two upper ridges...an upper trough is forming over the Canary Islands and inverted upper trough is forming west of the Cape Verde Islands.

P7...Tropical wave moving across the west Caribbean and into the southern Gulf of Mexico and SE Mexico is suppressed by upper vorticity discussed in paragraph P5.

P8...Tropical wave approaching the Lesser Antilles is able to produce some t-storm activity while receiving enhanced poleward upper outflow on the west flank of the E Atlantic upper ridge in paragraph P6. Dry air mentioned in paragraph P3 is limiting the expanse of this new t-storm activity.

P9...Tropical wave over the Cape Verde Islands in the previous disucssion is now west of those islands. A somewhat organized low pressure spin and t-storms have developed on the south end of this tropical wave...perhaps enhanced by some equatorward upper outflow on the west flank of the new inverted upper trough mentioned in the last sentence of paragraph P6. The above thermo birdseye chart suggests moisture associated with the tropical wave continues pushing out some of the dry air mentioned in paragraph P3.

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2012 Atlantic Hurricane Season Birdseye Discussion #55

By: NCHurricane2009, 7:13 AM GMT on July 18, 2012

...JULY 18 2012...3:15 AM EDT...
Atlantic tropics remain quiet as we push into the second half of July.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...

This chart is generated based on surface analysis from the National Hurricane Center TAFB at 0000Z, and the 0124Z-released HPC analysis.

In light blue is upper air analysis, with 200 mb wind barbs calculated by GOES satellite imagery showing the upper-level wind direction. Based on the 200 mb wind barbs, blue-dashed lines are locations of upper troughs, blue-zig-zag lines are locations of upper ridges. Blue Ls are locations of upper lows, blue Hs are locations of upper ridges.

In red is surface analysis, with solid lines indicating locations of surface fronts, dashed lines indicating locations of surface troughs, and zig-zag lines indicating surface ridge axes. Ls indicate surface lows, Hs indicate surface highs.

...THERMODYNAMICS BIRDSEYE CHART...

This chart is generated using GOES water vapor satellite imagery. Brown indicates dry air. White, blue, and purple indicates moist air. An increase in moisture indicates slower air parcel lapse rates with elevation and hence an increase toward instability.

Sea-surface temperatures are overlaid with light blue isotherms. The 26 deg C isotherm is highlighted in red. Waters at and south of the 26 deg C isotherm indicate low-level warmth and hence faster environmental lapse rates with elevation (more instability). Waters north of the 26 deg C isotherm indicate slower environmental lapse rates with elevation (less instability).

...MID-LATITUDES DISCUSSION...
P1...Hudson Bay frontal cyclone and its supporting upper trough have split into two cyclones....one upper trough and surface 1006 mb cyclone SW of Greenland...and a second upper trough and surface 1003 mb cyclone just east of Hudson Bay. Cut-off upper vortex over Texas left behind by this system persists...while the Great Lakes upper anticyclone has shifted southwestard into the central US due to cool air advection behind the 1003 mb cyclone. Upper convergence behind the Texas cut-off upper vortex supports a 1014 mb ridge over the SW US.

P2...Surface cyclone south of Greenland and its upper trough are making landfall into western Europe. South fragment of the upper trough E of Bermuda persists...and the 1010 mb frontal depression ENE of Bermuda it supported merged with the surface trough disturbance ESE of Bermuda mentioned in paragraph P6 of the previous discussion. What is left of this surface feature is now a surface trough located well east of Bermuda. The upper trough has also left behind another fragment west of the Azores.

P3...Open Atlantic surface ridge has multiple centers this early morning. Convergence south of the central US upper anticyclone (paragraph P1) supports a 1016 mb center over US Gulf coast. Convergence SE of Bermuda-area upper ridge (paragraph P5) supports a 1021 mb center S of Bermuda. Convergence southwest of the upper trough moving into Europe (paragraph P2) supports a 1030 mb center near the Azores. In conjunction with the south side of the upper ridge in paragraph P6...south side of this surface ridge is helping to waft Africa desert dry air westward across the Atlantic tropics.

...TROPICAL BELT DISCUSSION...
P4...Upper ridge covering the south Caribbean Sea has an anticyclonic center over Panama.

P5...Upper vorticity in the southern Gulf of Mexico persists...and extends to another upper vortex at the FL/GA border. Gulf portion of surface trough has dissipated...while the Florida portion is still supported by divergence between the S Gulf vortex and FL/GA vortex. Bermuda-area upper ridge perists east of all this upper vorticity.

P6...East Atlantic upper ridge persists. Disorganized upper vorticity is still located west of the upper ridge...located toward the E Caribbean Sea. 24 hrs ago...this upper ridge was split in half by inverted upper trough over the Cape Verde Islands retrograding westward. This inverted upper trough is now weaker (located midway between the Cape Verdes and Lesser Antilles)...allowing the two cells of this upper ridge to re-merge into a single upper anticyclone located south of the Azores.

P7...Tropical wave in the central Caribbean is moving toward the west Caribbean and southern Gulf of Mexico...where it will become suppressed by upper vorticity discussed in paragraph P5.

P8...Tropical wave midway between the Cape Verde Islands and Lesser Antilles in the previous discussion is approaching the Lesser Antilles this early morning. Dry air mentioned in paragraph P3 is suppressing this tropical wave.

P9...Tropical wave that was rolling off of Africa in the previous discussion is now over the Cape Verde Islands per current NHC TAFB maps. Inverted upper trough in paragraph P6 is now weaker and too far away to enhance the western upper outflow of this tropical wave...so its storm activity is limited thanks to a non-divergent uniform easterly flow on the south side of the upper ridge in paragraph P6. Despite limited storm activity at this time...the above thermo birdseye chart suggests moisture associated with the tropical wave is pushing out some of the dry air mentioned in paragraph P3.

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2012 Atlantic Hurricane Season Birdseye Discussion #54

By: NCHurricane2009, 4:10 AM GMT on July 17, 2012

...JULY 17 2012...12:15 AM EDT...
Pop-up disturbance east-southeast of Bermuda still not expected to develop in the midst of high surface pressures (see paragraph P6). Pop-up weather east of Florida also not showing development in the midst of high surface pressures (also see paragraph P6).

...ATMOSPHERIC FEATURES BIRDSEYE CHART...

This chart is generated based on surface analysis from the National Hurricane Center TAFB at 1800Z, and the 1927Z-released HPC analysis.

In light blue is upper air analysis, with 200 mb wind barbs calculated by GOES satellite imagery showing the upper-level wind direction. Based on the 200 mb wind barbs, blue-dashed lines are locations of upper troughs, blue-zig-zag lines are locations of upper ridges. Blue Ls are locations of upper lows, blue Hs are locations of upper ridges.

In red is surface analysis, with solid lines indicating locations of surface fronts, dashed lines indicating locations of surface troughs, and zig-zag lines indicating surface ridge axes. Ls indicate surface lows, Hs indicate surface highs.

...THERMODYNAMICS BIRDSEYE CHART...

This chart is generated using GOES water vapor satellite imagery. Brown indicates dry air. White, blue, and purple indicates moist air. An increase in moisture indicates slower air parcel lapse rates with elevation and hence an increase toward instability.

Sea-surface temperatures are overlaid with light blue isotherms. The 26 deg C isotherm is highlighted in red. Waters at and south of the 26 deg C isotherm indicate low-level warmth and hence faster environmental lapse rates with elevation (more instability). Waters north of the 26 deg C isotherm indicate slower environmental lapse rates with elevation (less instability).

...MID-LATITUDES DISCUSSION...
P1...Hudson Bay frontal cyclone and its supporting upper trough are slowly shifting east. Likewise...the east North America upper ridge supported by warm air advection ahead of this frontal system has shifted east into the W Atlantic and merged with the Bermuda-Bahamas upper ridge in paragraph P6. Cut-off upper vortex over Texas left behind by this system persists...but the cut-off upper anticyclone over the SE US has merged with the next upper ridge in the mid-latitudes...resulting in a single upper anticyclone over the Great Lakes. Upper convergence behind the Texas cut-off upper vortex supports a 1016 mb ridge over the SW US.

P2...Surface 998 mb cyclone south of Greenland and its upper trough are beginning to shift eastward toward Europe while weakening to 1000 mb. Expect additional weakening to continue as the surface cyclone is beneath the less divergent axis of the upper trough. South fragment of the upper trough is fracturing E of Bermuda...its eastern divergence supporting a 1010 mb frontal depression ENE of Bermuda.

P3...Cut-off upper trough SW of the Azores is merging with the upper trough mentioned in paragraph P2.

P4...Open Atlantic surface ridge has dissolved into multiple centers from the eastern US all the way toward Europe without a clear-cut upper convergent source to support a dominant surface ridge center. Convergence south of the Great Lakes upper anticyclone (paragraph P1) supports a 1018 mb center over the SE US...and convergence SE of the Bahamas-Bermuda upper ridge (paragraph P6) supports a 1020 mb center S of Bermuda. This surface ridge is split in half by weak surface trough disturbance ESE of Bermuda mentioned in paragraph P6. In conjunction with the south side of the upper ridge in paragraph P7...south side of this surface ridge is helping to waft Africa desert dry air westward across the Atlantic tropics.

...TROPICAL BELT DISCUSSION...
P5...Upper ridge covering the south half of the Caribbean Sea persists.

P6...Upper vorticity in the southern Gulf of Mexico persists...and extends to another upper vortex offshore of the Carolinas. In the past 24 hours...the upper vortex offshore of Carolinas has shifted west into the FL/GA border while retrograding about the Great Lakes upper anticyclone in paragraph P1. Florida surface trough has merged with the south Gulf surface trough...the Florida portion still supported by divergence between the S Gulf vortex and FL/GA vortex...and the south Gulf portion still supported by divergence between the S Gulf vortex and Texas vortex in paragraph P1. Bahamas-Bermuda upper ridge perists east of all this upper vorticity...and directional divergence between the upper ridge and upper vorticity supported concentrated t-storm clouds east of Florida that show no signs of tropical development...thanks to high surface pressures of the surface ridge in paragraph P4. 24 hrs ago...the outflow of the Bahamas-Bermuda upper ridge created a surface trough disturbance ESE of Bermuda...but the Bahamas-Bermuda upper ridge has been pushed westward away from the disturbance as the south fragment of the upper trough in paragraph P2 digs in. Because the weak surface trough disturbance is in the midst of high surface pressures of the ridge in paragraph P4...and because of increased southwesterly vertical shear ahead of the upper trough fragment...I still do not expect tropical cyclone development here. It is possible the surface trough disturbance gets absorbed by the 1010 mb frontal depression mentioned in paragraph P2.

P7...East Atlantic upper ridge persists...still featuring an anticyclonic center WNW of the Cape Verde Islands. Disorganized upper vorticity is still located west of the anticyclonic center...toward the Lesser Antilles and E Caribbean Sea. Upper trough from over the Cape Verde Islands is now an inverted feature getting ready to turn west about the south side of the anticyclonic center.

P8...North end of tropical wave in the central Caribbean is producing a streak of t-storm clouds that was over Haiti as of 1800Z earlier this evening. This t-storm activity is assisted by a directionally divergent upper northwesterly jet between the S Caribbean upper ridge in paragraph P5 and disorganized E Caribbean upper vorticity in paragraph P7. As such...this t-storm activity is also in hositle northwesterly vertical shear. It appears in the next 24 hours...the north end of this tropical wave will be adding to the t-storms east of Florida mentioned in paragraph P6.

P9...Tropical wave nearing the Lesser Antilles has been dropped from NHC TAFB maps as if it dissipated.

P10...Finally...NHC TAFB has added the tropical wave SW of the Cape Verde Islands to their maps...this after three days of having to track the tropical wave without assistance from NHC TAFB. This tropical wave is now midway between the Cape Verde Islands and Lesser Antilles. Dry air in paragraph P4 is suppressing this tropical wave.

P11...Last night...suspicion was that a tropical wave was rolling off the coast of Africa based on satellite animation. This has proven correct...as the NHC TAFB have added it to thier maps. Although the inverted upper trough near the Cape Verde Islands in paragraph P7 is enhancing the western upper outflow of this tropical wave...dry air (in paragraph P4) appears to be suppressing its t-storm activity.

Updated: 4:14 AM GMT on July 17, 2012

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2012 Atlantic Hurricane Season Birdseye Discussion #53

By: NCHurricane2009, 3:34 AM GMT on July 16, 2012

...JULY 15 2012...11:35 PM EDT...
It appears tropical wave has lost its chances of developing east of the Lesser Antilles (see paragraph P10). New pop-up disturbance east-southeast of Bermuda showing no signs of developing in the midst of high surface pressures (see paragraph P6).

...ATMOSPHERIC FEATURES BIRDSEYE CHART...

This chart is generated based on surface analysis from the National Hurricane Center TAFB at 1800Z, and the 1930Z-released HPC analysis.

In light blue is upper air analysis, with 200 mb wind barbs calculated by GOES satellite imagery showing the upper-level wind direction. Based on the 200 mb wind barbs, blue-dashed lines are locations of upper troughs, blue-zig-zag lines are locations of upper ridges. Blue Ls are locations of upper lows, blue Hs are locations of upper ridges.

In red is surface analysis, with solid lines indicating locations of surface fronts, dashed lines indicating locations of surface troughs, and zig-zag lines indicating surface ridge axes. Ls indicate surface lows, Hs indicate surface highs.

...THERMODYNAMICS BIRDSEYE CHART...

This chart is generated using GOES water vapor satellite imagery. Brown indicates dry air. White, blue, and purple indicates moist air. An increase in moisture indicates slower air parcel lapse rates with elevation and hence an increase toward instability.

Sea-surface temperatures are overlaid with light blue isotherms. The 26 deg C isotherm is highlighted in red. Waters at and south of the 26 deg C isotherm indicate low-level warmth and hence faster environmental lapse rates with elevation (more instability). Waters north of the 26 deg C isotherm indicate slower environmental lapse rates with elevation (less instability).

...MID-LATITUDES DISCUSSION...
P1...Hudson Bay frontal system and its supporting upper trough are beginning to shift east. Likewise...the east North America upper ridge supported by warm air advection ahead of this frontal system is shifting east. Whatever of the upper trough and upper ridge that is not shifting east is now a cut-off upper vortex over Texas and cut-off upper anticyclone over the SE US. Upper convergence behind the upper trough supports a 1019 mb ridge over central Canada...and upper convergence behind the Texas cut-off upper vortex supports a 1019 mb ridge over the SW US.

P2...Surface 998 mb cyclone south of Greenland and its upper trough are beginning to shift eastward toward Europe. Although the surface cyclone has not yet weakened...expect this to happen any time now as it is beneath the less divergent axis of the upper trough. Upper convergence on the back side of this upper trough is supporting a 1019 mb ridge over Newfoundland.

P3...Cut-off upper vortex SW of the Azores has opened into an upper trough as it begins merging with upper trough mentioned in paragraph P2.

P4...Open Atlantic surface ridge has dissolved into multiple centers from the eastern US all the way toward Europe without a clear-cut upper convergent source to support a dominant surface ridge center. In conjunction with the south side of the upper ridge in paragraph P7...south side of this surface ridge is helping to waft Africa desert dry air westward across the Atlantic tropics.

...TROPICAL BELT DISCUSSION...
P5...Upper ridge covering the south half of the Caribbean Sea has produced a blow-up of t-storms over E Honduras...E Nicaragua...and Costa Rica with a divergent upper anticyclonic center.

P6...Caribbean area upper vorticity has all shifted into the southern Gulf of Mexico...and extends to a new upper vortex offshore of the Carolinas. The eastern inflow of this upper vorticity has been diverging heavily with the western inflow of the cut-off upper vortex in paragraph P3...the divergence resulting in widespread cloudiness from near Bermuda all the way to Florida...and resulting in a new surface trough over Bermuda and the waters SW that has now moved into Florida. This Florida surface trough is now supported by divergence between the upper vortex in the south Gulf and upper vortex offshore of the Carolinas. There is also a new upper ridge just NE of Bermuda that separates this upper vorticity from the upper vortex in paragraph P3...and this upper ridge has recently expanded into the Bahamas. The outflow of this upper ridge has created a circular t-storm burst ESE of Bermuda and weak surface trough. Because the weak surface trough is in the midst of high surface pressures of the ridge in paragraph P4...and because the surface trough is located east rather than under the circular storm burst...I do not expect tropical cyclone development. Louisiana coast surface trough has dissipated...but its southward west Caribbean extension that formed yesterday has moved into the southern Gulf of Mexico while now supported by divergence between the south Gulf upper vortex and cut-off Texas upper vortex in paragraph P1.

P7...East Atlantic upper ridge persists...still featuring an anticyclonic center WNW of the Cape Verde Islands that has begun a southwestward shift predicted by computer models...thanks to the merger between the paragraph P3 upper vortex and upper trough in paragraph P2 that is pushing the anticyclonic center. Disorganized upper vorticity is still located west of the anticyclonic center...toward the Lesser Antilles and E Caribbean Sea. Upper trough from Canary Islands has shifted southward to the Cape Verde Islands while orbiting the east side of the anticyclonic center.

P8...Tropical wave in the eastern Caribbean is moving into the central Caribbean. It is suppressed by southwesterly vertical shear induced by the upper vorticity mentioned in paragraph P6.

P9...Tropical wave midway between the Cape Verdes and Lesser Antilles is now nearing the Lesser Antilles. It is suppressed by dry air mentioned in paragraph P4.

P10...Satellite animation suggests there is still a possible tropical wave SW of the Cape Verde Islands. This is the third time I have analyzed this wave in the above birdseye charts while the NHC TAFB maps have yet to acknowledge it...so my confidence in the existence of this tropical wave is decreasing. If this tropical wave has existed...continued northerly shear on the east flank of the upper anticyclonic center in paragraph P7 has allowed the dry air in paragraph P4 to intrude from the north. Paragraph P7 explains that the upper anticyclonic center is shifting southwest as the models have been predicting...which would mean eventual vertical alignment with this tropical wave...and hence good upper outflow enhancement. However...the expanse of the dry air intrusion now tells me tropical cyclone development is out the window despite the potential for upper outflow enhancement in the future.

P11...Satellite imagery suggests yet another tropical wave is rolling off the coast of Africa. I am gun shy to add this possible tropical wave to the above birdseye charts until if/when NHC TAFB adds the tropical wave in paragraph P10 to their charts. The upper trough headed toward the Cape Verde Islands in paragraph P7 may enhance the western upper outflow of this possible tropical wave...but dry air (in paragraph P4) is likely to be a challenge as it has been for the past several tropical waves.

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2012 Atlantic Hurricane Season Birdseye Discussion #52

By: NCHurricane2009, 5:08 AM GMT on July 15, 2012

...JULY 15 2012...1:20 AM EDT...
Still watching to see if tropical wave develops in waters east of the Lesser Antilles...prior to reaching unfavorable upper winds (see paragraph P10). Otherwise...the Atlantic tropics remain calm.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...

This chart is generated based on surface analysis from the National Hurricane Center TAFB at 0000Z, and the 0129Z-released HPC analysis.

In light blue is upper air analysis, with 200 mb wind barbs calculated by GOES satellite imagery showing the upper-level wind direction. Based on the 200 mb wind barbs, blue-dashed lines are locations of upper troughs, blue-zig-zag lines are locations of upper ridges. Blue Ls are locations of upper lows, blue Hs are locations of upper ridges.

In red is surface analysis, with solid lines indicating locations of surface fronts, dashed lines indicating locations of surface troughs, and zig-zag lines indicating surface ridge axes. Ls indicate surface lows, Hs indicate surface highs.

...THERMODYNAMICS BIRDSEYE CHART...

This chart is generated using GOES water vapor satellite imagery. Brown indicates dry air. White, blue, and purple indicates moist air. An increase in moisture indicates slower air parcel lapse rates with elevation and hence an increase toward instability.

Sea-surface temperatures are overlaid with light blue isotherms. The 26 deg C isotherm is highlighted in red. Waters at and south of the 26 deg C isotherm indicate low-level warmth and hence faster environmental lapse rates with elevation (more instability). Waters north of the 26 deg C isotherm indicate slower environmental lapse rates with elevation (less instability).

...MID-LATITUDES DISCUSSION...
P1...Central US surface frontal system has dissipated...but leaves behind its supporting upper trough. Another frontal system diving SE from western Canada has arrived to central Canada via Hudson Bay...and its upper trough has merged with the central US upper trough. Upper convergence behind the central US upper trough supports a surface 1018 mb ridge over the western US. Finally...warm air advection ahead of the Hudson Bay frontal system supports an upper ridge covering the eastern US and eastern Canada.

P2...Complex frontal system stretching from the SE US all the way toward Europe has consolidated in the north Atlantic south of Greenland. Upper trough heading toward Europe has made landfall....no longer in the scope of this blog. Upper trough that moved offshore from eastern Canada yesterday is now south of Greenland while supporting the 998 mb surface cyclone in the area. This surface cyclone has maintained strength in the past 24 hours...but now that it is beneath the less divergent axis of the upper trough...expect it to begin decaying.

P3...Cut-off upper vortex SW of the Azores persists. Cut-off upper trough over the Canary Islands is digging southward while orbiting the anticyclonic center of the upper ridge in paragraph P7...and as such this feature has been moved to paragraph P7.

P4...Open Atlantic surface ridge center has weakened from 1030 mb to 1028 mb in the last 24 hours. I had expected this weakening yesterday as the ridge center was beneath upper divergence on the NE quad of the upper vortex in paragraph P4. Now that the surface ridge center has relocated westward beneath the upper convergence on the NW quad of this upper vortex...expect the surface ridge to maintain strength. South side of this surface ridge is helping to waft Africa desert dry air westward across the Atlantic tropics.

...TROPICAL BELT DISCUSSION...
P5...Central America upper ridge now covers the south half of the Caribbean Sea.

P6...Caribbean area upper vorticity is dominated by large scale upper vortex that was N of the Caribbean Islands 24 hrs ago. Now...this large upper vortex is entering the southern Gulf of Mexico while retrograding about the east US upper ridge in paragraph P1. The eastern inflow of this upper vorticity diverges heavily with the western inflow of the cut-off upper vortex in paragraph P3...the divergence resulting in widespread cloudiness from near Bermuda all the way to western Cuba...and resulting in a new surface trough over Bermuda and the waters SW. There is also a new upper ridge just NE of Bermuda that separates this upper vorticity from the upper vortex in paragraph P3. E Gulf of Mexico 1015 mb low is tracking WNW into Louisiana while weakening into a surface trough...steered about the SW quad of the open Atlantic surface ridge (paragraph P4). Recently...this surface trough has been extended southward into the western Caribbean...perhaps caused by the divergent westerly jet between the upper vorticity discussed in this paragraph and upper ridge in paragraph P5. Alternatively...the southward extension of this surface trough may be the tropical wave from which this surface trough originated.

P7...East Atlantic upper ridge persists...still featuring an anticyclonic center WNW of the Cape Verde Islands. The embedded inverted upper trough on the south side has ejected westward about the anticyclonic center...and is now disorganized upper vorticity located toward the Lesser Antilles. The Canary Islands upper trough on the northeast side (paragraph P3) is moving southward about the anticyclonic center and toward the Cape Verde Islands.

P8...Tropical wave approaching the Lesser Antilles in the previous discussion has crossed the islands into the eastern Caribbean. It is suppressed by westerly vertical shear induced by the upper vorticity mentioned in paragraph P6.

P9...Tropical wave midway between the Cape Verdes and Lesser Antilles is speeding westward toward the Lesser Antilles. The western side of the tropical wave is suppressed by dry air mentioned in paragraph P4. Surface convergence on the east side of the the tropical wave...coupled with enhanced poleward upper outflow (induced by west flank of upper anticyclonic center trough in paragraph P7)...is creating a moist air buffer seen in the above thermo birdseye chart.

P10...Satellite animation suggests the tropical wave SE of the Cape Verde Islands in the previous discussion is now SW of the islands. This is the second time I have analyzed this wave in the above birdseye charts while the NHC TAFB maps have yet to acknowledge it...but I am confident that the tropical wave exists. Satellite animation suggests the t-storms of the tropical wave have been squashed into its south half...and the t-storms have become less distinguishable within an east-west ITCZ band. This tells me the tropical wave has been affected by northerly shear on the east flank of the upper anticyclone in paragraph P7...and this shear has also allowed the dry air in paragraph P4 to intrude into the north half of the tropical wave. However...there is still a moisture buffer west of the tropical wave as explained at the end of paragraph P9...and the GFS model still suggests the upper anticyclone in paragraph P7 will be pushed southward by a merger between the cut-off upper vortex in paragraph P3 and upper trough in paragraph P2. The southward displacement of this upper anticyclone would enhance the upper outflow of the tropical wave. Moreover...the GFS model suggests this upper anticyclone should shift westward...thanks to Canary Islands upper trough (paragraphs P3 and P7) digging southward toward the Cape Verde Islands. Because model runs do not show this upper anticyclone expanding westward beyond the Lesser Antilles...I think this tropical wave has a chance to become a tropical disturbance (such as an "Invest" on the Navy NRL site)...or at most a weak tropical cyclone...while it is east of the Lesser Antilles. Beyond that...it looks like unfavorable upper winds will stop this wave from developing.

Updated: 5:08 AM GMT on July 15, 2012

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2012 Atlantic Hurricane Season Birdseye Discussion #51

By: NCHurricane2009, 4:48 AM GMT on July 14, 2012

...JULY 14 2012...12:50 AM EDT...
While tropical development is no longer expected in the eastern Gulf of Mexico (paragraph P7)...next tropical wave emerging from Africa has potential to develop (paragraph P11).

...ATMOSPHERIC FEATURES BIRDSEYE CHART...

This chart is generated based on surface analysis from the National Hurricane Center TAFB at 1800Z, and the 1930Z-released HPC analysis.

In light blue is upper air analysis, with 200 mb wind barbs calculated by GOES satellite imagery showing the upper-level wind direction. Based on the 200 mb wind barbs, blue-dashed lines are locations of upper troughs, blue-zig-zag lines are locations of upper ridges. Blue Ls are locations of upper lows, blue Hs are locations of upper ridges.

In red is surface analysis, with solid lines indicating locations of surface fronts, dashed lines indicating locations of surface troughs, and zig-zag lines indicating surface ridge axes. Ls indicate surface lows, Hs indicate surface highs.

...THERMODYNAMICS BIRDSEYE CHART...

This chart is generated using GOES water vapor satellite imagery. Brown indicates dry air. White, blue, and purple indicates moist air. An increase in moisture indicates slower air parcel lapse rates with elevation and hence an increase toward instability.

Sea-surface temperatures are overlaid with light blue isotherms. The 26 deg C isotherm is highlighted in red. Waters at and south of the 26 deg C isotherm indicate low-level warmth and hence faster environmental lapse rates with elevation (more instability). Waters north of the 26 deg C isotherm indicate slower environmental lapse rates with elevation (less instability).

...MID-LATITUDES DISCUSSION...
P1...Frontal system from central Canada has dived SE into the central US. Its supporting upper trough has merged with central US upper trough from paragraph P3...and the central US upper trough looks to be re-enforced by cool air advection from another frontal system diving SE from western Canada. Upper convergence behind the central US upper trough supports a surface 1017 mb ridge over the western US. Finally...warm air advection ahead of the central US frontal system supports an upper ridge wave that has moved into the eastern US and merged with Florida upper ridge in paragraph P7.

P2...North Atlantic upper ridge has merged with east tropical Atlantic upper ridge in paragraph P8.

P3...Complex frontal system stretching from the SE US all the way toward Europe persists. Upper trough heading toward Europe is approaching landfall. Upper trough over eastern Canada has moved offshore while its eastern divergence has strengthened the northwest Atlantic surface cyclone to 998 mb as of 1930Z...and its western convergence supports a 1019 mb ridge over E Hudson Bay and 1025 mb ridge over the NE US. The central US upper trough is now part of frontal system discussed in paragraph P1.

P4...Cut-off upper vortex SW of the Azores has stalled with the dissipation of the steering upper ridge in paragraph P2. Cut-off upper trough over the Canary Islands persists.

P5...Open Atlantic surface ridge still has a strong center...1031 mb SW of the Azores as of 1800Z. It is now beneath upper divergence on the NE quad of the upper vortex in pagragraph P4...so this surface ridge is likely to weaken some in the next 24 hours. South side of this surface ridge is helping to waft Africa desert dry air westward across the Atlantic tropics.

...TROPICAL BELT DISCUSSION...
P6...Central America upper ridge persists...with a divergent anticyclonic center over the Panama area enhancing t-storms below.

P7...Caribbean upper vorticity has merged with large upper vortex N of the Caribbean Islands in paragraph P8. The eastern inflow of this upper vorticity diverges heavily with the western inflow of the cut-off upper vortex in paragraph P4...the divergence resulting in widespread cloudiness south of Bermuda. This upper vorticity still extends to an upper low in the southern Gulf of Mexico. As the upper vortex N of the Caribbean Islands moves westward toward upper vortex in the south Gulf...the Florida upper ridge has been pushed northward such that it has merged with the upper ridge mentioned in paragraph P1. Surface tropical wave in the area has moved into the eastern Gulf of Mexico while maturing into a 1015 mb low thanks to upper divergence supplied by Florida upper ridge. The 1015 mb low is tracking WNW toward the US Gulf coast about the SW quad of the 1025 mb surface ridge (paragraph P3) and open Atlantic surface ridge (paragraph P5). With the 1015 mb low soon to move over land and moving away from the divergent core of the Florida upper ridge...tropical cyclone development is not possible.

P8...Large scale upper vortex north of the Caribbean Islands has merged with Caribbean area upper vorticity mentioned in paragraph P7. Behind this...the east Atlantic upper ridge has rebuilt from western Africa...now featuring an anticyclonic center present WNW of the Cape Verde Islands and embedded inverted upper trough west of the Cape Verde Islands.

P9...Tropical wave midway between the Cape Verde Islands and Lesser Antilles in previous discussion is approaching the Lesser Antilles. It still features a surface low on its south end that has weakened to 1010 mb. It has exited the unfavorable dry air mentioned in paragraph P5...but is now entering the unfavorable westerly vertical shear induced by the upper vorticity mentioned in paragraph P7. A southwesterly jet on the SE flank of this upper vorticity may enhance the poleward upper outflow of this tropical wave...so some shower or t-storm activity is possible as the tropical wave crosses the Lesser Antilles in the next 24 hours.

P10...Tropical wave over the Cape Verde Islands in the previous discussion has moved quickly west to the waters midway between the Cape Verdes and Lesser Antilles. The western side of the tropical wave is suppressed by dry air mentioned in paragraph P5. Surface convergence on the east side of the the tropical wave...coupled with enhanced poleward upper outflow (induced by east flank of inverted upper trough in paragraph P8)...has significantly increased t-storm activity SW of the Cape Verde Islands.

P11...Satellite imagery suggests the next tropical wave had just rolled off of Africa...and is currently SE of the Cape Verde Islands. It has a decent structure with good spin and t-storm bursts on satellite animation. The tropical wave in paragraph P10 is producing a large area of t-storms SW of the Cape Verde Islands that is protecting this tropical wave from the dry air in paragraph P5. Moreover..a gander at the GFS model suggests the upper winds could become favorable thru the next 72 hours...so this tropical wave appears to have potential to become a tropical cyclone. The GFS model suggests that the anticyclonic center of the paragraph P8 upper ridge will be pushed southward by a merger between the cut-off upper vortex in paragraph P4 and east Canada upper trough in paragraph P3. The southward displacement of this upper anticyclonic center would enhance the upper outflow of the tropical wave. Morover...the GFS model suggests this anticyclonic center should shift westward with the tropical wave...thanks to Canary Islands upper trough in paragraph P4 forecast to dig southward toward the Cape Verde Islands.

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2012 Atlantic Hurricane Season Birdseye Discussion #50

By: NCHurricane2009, 4:30 AM GMT on July 13, 2012

...JULY 13 2012...12:40 AM EDT...
Tropical cyclone development in the eastern Gulf of Mexico looking less likely. See paragraph P7 for details.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...

This chart is generated based on surface analysis from the National Hurricane Center TAFB at 1800Z, and the 1934Z-released HPC analysis.

In light blue is upper air analysis, with 200 mb wind barbs calculated by GOES satellite imagery showing the upper-level wind direction. Based on the 200 mb wind barbs, blue-dashed lines are locations of upper troughs, blue-zig-zag lines are locations of upper ridges. Blue Ls are locations of upper lows, blue Hs are locations of upper ridges.

In red is surface analysis, with solid lines indicating locations of surface fronts, dashed lines indicating locations of surface troughs, and zig-zag lines indicating surface ridge axes. Ls indicate surface lows, Hs indicate surface highs.

...THERMODYNAMICS BIRDSEYE CHART...

This chart is generated using GOES water vapor satellite imagery. Brown indicates dry air. White, blue, and purple indicates moist air. An increase in moisture indicates slower air parcel lapse rates with elevation and hence an increase toward instability.

Sea-surface temperatures are overlaid with light blue isotherms. The 26 deg C isotherm is highlighted in red. Waters at and south of the 26 deg C isotherm indicate low-level warmth and hence faster environmental lapse rates with elevation (more instability). Waters north of the 26 deg C isotherm indicate slower environmental lapse rates with elevation (less instability).

...MID-LATITUDES DISCUSSION...
P1...Frontal system from western Canada is moving into central Canada. Warm air advection ahead of this system supports an upper ridge wave over central Canada...while the upper ridge over the western US once supported by the same warm air advection is left behind.

P2...North Atlantic upper ridge persists via support of southwesterly warm air advection ahead of complex frontal system discussed in paragraph P3.

P3...Northwest Atlantic surface cyclone and its supporting longwave upper trough have degenerated into a less organized...complex frontal system stretching from the SE US all the way toward Europe. At the surface...the northwest Atlantic surface cyclone is diffuse with multiple low pressure centers on the east coast of Canada...in the vicinity of Greenland...and heading into western Europe. There are also surface frontal depressions in the western Atlantic and SE US supported by eastern divergence of the longwave upper troughing. The longwave upper troughing has decomposed into one trough heading toward Europe...another over east Canada...and a third over the central US. Upper convergence on the back side of the longwave upper troughing supports a 1017 mb surface ridge over E Hudson Bay...1022 mb ridge over the Great Lakes...and 1017 mb ridge over the SW US.

P4...Northeast Atlantic upper trough has moved into Europe...but leaves behind a cut-off upper vortex SW of the Azores retrograding westward about the upper ridge in paragraph P2...and a cut-off upper trough over the Canary Islands.

P5...Open Atlantic surface ridge still has a strong center...1032 mb SW of the Azores as of 1800Z...now supported by upper convergence between southerlies (on the NE flank of the cut-off upper vortex in paragraph P4) and easterlies (on the south side of the upper ridge in paragraph P2). In conjunction with upper ridge in paragraph P2...south side of this surface ridge is helping to waft Africa desert dry air westward across the Atlantic tropics.

...TROPICAL BELT DISCUSSION...
P6...Central America and northern South America upper ridge persists...with divergence on its southwest side supporting t-storm activity over the Panama area.

P7...Caribbean upper vorticity has elongated into a few features while wedged between the Central America upper ridge in paragraph P6 and North Atlantic upper ridge in paragraph P2. This upper vorticity still extends to an upper low in the southern Gulf of Mexico...while its upper trough near the Bahamas has been absorbed by incoming upper vortex mentioned in paragraph P8. There is still a divergent Florida upper ridge separating the south Gulf upper vortex from the incoming vortex in paragraph P8...but the mid-level low and tropical wave below have not taken much advantage of the upper ridge as they both push into the eastern Gulf of Mexico (sat imagery suggests the mid-level low is moving west over Tampa and heading into the Gulf). The tropical wave and mid-level low are now running out of time to develop beneath the Florida upper ridge before moving into the less favorable environment beneath the south Gulf upper vortex. NAM model still suggests tropical development...and tracks it WNW toward the Louisiana coast about the SW quad of the Great Lakes surface ridge (paragraph P3) and open Atlantic surface ridge (paragraph P5). GFS model still shows no tropical development.

P8...Large scale upper vortex from the eastern Atlantic is ejecting westward and passing north of the Caribbean Islands while retrograding about the upper ridge in paragraph P2. The eastern inflow of this upper vortex diverges heavily with the western inflow of the cut-off upper vortex in paragraph P4...the divergence resulting in widespread t-storm activity across the eastern semicircle of this upper vortex. Behind the retreating upper vortex...the east Atlantic upper ridge is rebuilding from western Africa.

P9...Tropical wave midway between the Cape Verde Islands and Lesser Antilles still features a 1008 mb surface swirl on its south end...and is still suppressed by dry air mentioned in paragraph P5. Outside of the dry air...the immediate environment of this tropical wave is favorable for development thanks to low shear on the south side of the rebuilding east Atlantic upper ridge in paragraph P8. However...I still expect the tropical wave to eventually encounter westerly vertical shear on the south side of the upper vortex also mentioned in paragraph P8.

P10...Tropical wave that has recently emerged from Africa is marked over the Cape Verde Islands as of 1800Z TAFB analysis. If the tropical wave in paragraph P9 is a good analogue...expect this tropical wave to become suppressed by dry air.

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2012 Atlantic Hurricane Season Birdseye Discussion #49

By: NCHurricane2009, 3:09 AM GMT on July 12, 2012

...JULY 11 2012...11:20 PM EDT...
Tropical cyclone formation in the eastern Gulf of Mexico is possible beginning 24 hours from now. See paragraph P7 for details.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...

This chart is generated based on surface analysis from the National Hurricane Center TAFB at 1800Z, and the 1929Z-released HPC analysis.

In light blue is upper air analysis, with 200 mb wind barbs calculated by GOES satellite imagery showing the upper-level wind direction. Based on the 200 mb wind barbs, blue-dashed lines are locations of upper troughs, blue-zig-zag lines are locations of upper ridges. Blue Ls are locations of upper lows, blue Hs are locations of upper ridges.

In red is surface analysis, with solid lines indicating locations of surface fronts, dashed lines indicating locations of surface troughs, and zig-zag lines indicating surface ridge axes. Ls indicate surface lows, Hs indicate surface highs.

...THERMODYNAMICS BIRDSEYE CHART...

This chart is generated using GOES water vapor satellite imagery. Brown indicates dry air. White, blue, and purple indicates moist air. An increase in moisture indicates slower air parcel lapse rates with elevation and hence an increase toward instability.

Sea-surface temperatures are overlaid with light blue isotherms. The 26 deg C isotherm is highlighted in red. Waters at and south of the 26 deg C isotherm indicate low-level warmth and hence faster environmental lapse rates with elevation (more instability). Waters north of the 26 deg C isotherm indicate slower environmental lapse rates with elevation (less instability).

...MID-LATITUDES DISCUSSION...
P1...Warm air advection ahead of frontal system from western Canada is re-building upper ridging over the western US.

P2...Westerly warm air advection south of the NW Atlantic cyclone in paragraph P2 has spread North America upper ridge across much of the north Atlantic. Some of this upper ridge is left behind along the US Gulf coast.

P3...Northwest Atlantic surface cyclone has moved offshore from eastern Canada with a diffuse surface center of 1000 mb as of 1929Z. The surface center continues decaying while beneath the less divergent core of its supporting longwave upper trough. Upper convergence behind the longwave upper trough supports a 1023 mb surface ridge over the Great Lakes. Split flow upper divergence between the SW edge of the longwave upper trough and north edge of the upper ridge in paragraph P1 supports t-storms...a long surface front...and frontal depressions across the SE US and west Atlantic...all trailing from the surface cyclone.

P4...Northeast Atlantic upper trough persists. It leaves behind a cut-off upper vortex southwest of the Azores that is currently retrograding westward around the upper ridge in paragraph P2.

P5...Open Atlantic surface ridge still has a strong center...1032 mb over the Azores as of 1800Z...which is supported by upper convergence on the back side of the NE Atlantic upper trough (paragraph P4). South side of this surface ridge is helping to waft Africa desert dry air westward across the Atlantic tropics.

...TROPICAL BELT DISCUSSION...
P6...Central America upper ridge persists...with divergence on its southwest side supporting t-storm activity over the Panama area.

P7...Caribbean upper vorticity has elongated into a few features while wedged between the Central America upper ridge in paragraph P6 and North Atlantic upper ridge in paragraph P2. This upper vorticity still extends to an upper low in the southern Gulf of Mexico...and upper trough near the Bahamas...with a divergent upper ridge between the two supporting t-storms across Florida that appear to have organized into a mid-level low pressure spin. Tropical wave that was over Hispaniola in the previous discussion is now over eastern Cuba and headed toward the mid-level low. Although the mid-level low's t-storms have pulsed down this evening...I would be cautious in discounting development due to the very favorable upper winds and good surface structure thanks to the incoming tropical wave and mid-level low. Therefore...I believe tropical cyclone development is possible in the eastern Gulf of Mexico beginning 24 hours from now. GFS model does not show development...but the NAM model hints at it. Model runs suggest the Great Lakes surface ridge in pagragraph P3 will merge with the paragraph P5 surface ridge...the SW quad of the merged ridge steering this tropical cyclone northwestward toward the US Gulf coast. A turn toward the west does not appear possible as the west Canada frontal system in paragraph P1 will cause a ridge weakness as it passes well to the north.

P8...Large scale upper vorticity exists across much of the eastern tropical Atlantic...an effect due to relatively lower pressures south of the upper ridge in paragraph P2. A large upper vortex is ejecting westward and passing north of the Lesser Antilles while retrograding about the upper ridge in paragraph P2. However...there is still an upper ridge toward the west coast of Africa...in relatively higher pressures south of the NE Atlantic upper trough (paragraph P4).

P9...Tropical wave west of the Cape Verde Islands is now midway between those islands and the Lesser Antilles...suppresed by dry air mentioned in paragraph P5. Southern inflow into the upper vorticity in paragraph P8 is enhancing the poleward upper outflow over the south end of this tropical wave...which has allowed the south end of the tropical wave to develop a 1008 mb surface low and t-storms in the last 24 hours. The westerly upper winds ahead of the tropical wave...generated by the same upper vorticity...are more stiff...and so I expect the new 1008 mb low to not develop as it will track into westerly vertical shear.

Updated: 4:20 AM GMT on July 12, 2012

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2012 Atlantic Hurricane Season Birdseye Discussion #48

By: NCHurricane2009, 3:06 AM GMT on July 11, 2012

...JULY 10 2012...11:05 PM EDT...
So far no signs of tropical development along frontal boundary...associated with deep-layered cyclone in Northwestern Atlantic (see paragraph P2).

I believe there is slight potential for a tropical disturbance in the eastern Gulf of Mexico beginning 48 hours from now. See paragraph P6 for details.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...

This chart is generated based on surface analysis from the National Hurricane Center TAFB at 1800Z, and the 1929Z-released HPC analysis.

In light blue is upper air analysis, with 200 mb wind barbs calculated by GOES satellite imagery showing the upper-level wind direction. Based on the 200 mb wind barbs, blue-dashed lines are locations of upper troughs, blue-zig-zag lines are locations of upper ridges. Blue Ls are locations of upper lows, blue Hs are locations of upper ridges.

In red is surface analysis, with solid lines indicating locations of surface fronts, dashed lines indicating locations of surface troughs, and zig-zag lines indicating surface ridge axes. Ls indicate surface lows, Hs indicate surface highs.

...THERMODYNAMICS BIRDSEYE CHART...

This chart is generated using GOES water vapor satellite imagery. Brown indicates dry air. White, blue, and purple indicates moist air. An increase in moisture indicates slower air parcel lapse rates with elevation and hence an increase toward instability.

Sea-surface temperatures are overlaid with light blue isotherms. The 26 deg C isotherm is highlighted in red. Waters at and south of the 26 deg C isotherm indicate low-level warmth and hence faster environmental lapse rates with elevation (more instability). Waters north of the 26 deg C isotherm indicate slower environmental lapse rates with elevation (less instability).

...MID-LATITUDES DISCUSSION...
P1...Upper ridge over North America has weakened due to cool air advection behind NW Atlantic cyclone in paragraph P2....except for the western US where warm air advection ahead of a frontal system pushing into western Canada is supporting a re-build of upper ridging. Westerly warm air advection south of the NW Atlantic cyclone has spread this upper ridge far eastward across much of the north Atlantic. Upper convergence on the south side of this upper ridge supported a surface ridge in the Gulf of Mexico that is presently weakening as explained in paragraph P6.

P2...Northwest Atlantic surface cyclone remains centered over eastern Canada with a diffuse surface center of 992 mb as of 1929Z. Now that the surface center has whirled beneath the less divergent core of its supporting longwave upper trough...expect the surface center to continue decaying. Upper convergence behind the longwave upper trough supports a 1022 mb surface ridge over the central US. Split flow upper divergence between the SW edge of the longwave upper trough and north edge of the upper ridge in paragraph P1 supports t-storms...a long surface front...and frontal depressions across the SE US...all trailing from the surface cyclone. If this trailing front and t-storm activity sags southward into the favorable low shear/enhanced outflow of the upper ridge in paragraph P1...then tropical development in the northwest Atlantic could be possible in the next days.

P3...Northeast Atlantic upper trough persists. Its eastern divergence supports a weak 1021 mb surface low north of the Canary Islands as of 1800Z.

P4...Open Atlantic surface ridge still has a strong center...1031 mb just west of the Azores as of 1800Z...which is supported by upper convergence on the back side of the NE Atlantic upper trough (paragraph P3). South side of this surface ridge is helping to waft Africa desert dry air westward across the Atlantic tropics.

...TROPICAL BELT DISCUSSION...
P5...Central America upper ridge has weakened due to loss of t-storm activity (and associated latent heat release) that supported it. Easterlies on the south side of this upper ridge diverge heavily with westerly flow going into the upper vorticity in paragraph P6. This upper divergence supports t-storm activity over the Panama area.

P6...Caribbean upper vorticity has elongated into a few features while wedged between the Central America upper ridge in paragraph P5...eastern Caribbean upper ridge in paragraph P7...and North America upper ridge in paragraph P1. This upper vorticity has an upper vortex in the central Caribbean. This upper vorticity also consists of an upper low in the southern Gulf of Mexico...and upper trough over the Bahamas...with split flow divergence at the boundary between these two eroding the Gulf surface ridge in paragraph P1...and supporting t-storms across Florida and eastern Gulf of Mexico. GFS computer model shows the southern Gulf upper low and Bahamas upper trough persisting...so I interpret that the favorable upper divergence between the two should persist. The tropical wave in paragraph P9 should arrive to this favorable upper divergence in the next 48 hours...so I now believe a tropical disturbance is possible in the eastern Gulf of Mexico by that time.

P7...Eastern Caribbean upper ridge persists.

P8...Expansive east Atlantic upper ridge has reversed to large-scale upper vorticity...an effect due to relatively lower pressures south of the upper ridge in paragraph P1 that has recently expanded across the north Atlantic. What is left of the east Atlantic upper ridge is toward the west coast of Africa...in relatively higher pressures south of the NE Atlantic upper trough (paragraph P3).

P9...Tropical wave crossing Puerto Rico in the previous discussion is now over Hispaniola and waters north. It is encountering unfavorable conditions thanks to westerly vertical shear from the Bahamas upper trough in paragraph P6...but divergence on the east side of this upper trough is allowing the north side of the tropical wave to produce t-storms NE of the Bahamas. See paragraph P6 for how this tropical wave may contribute to an eastern Gulf of Mexico disturbance beginning 48 hours from now.

P10...Tropical west of the Cape Verde Islands remains suppressed by dry air mentioned in paragraph P4..and is also suppressed by upper convergence directly beneath the new upper vorticity mentioned in paragraph P8.

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2012 Atlantic Hurricane Season Birdseye Discussion #47

By: NCHurricane2009, 2:01 AM GMT on July 10, 2012

...JULY 9 2012...10:02 PM EDT...
Still Watching thunderstorm activity along frontal boundary...associated with deep-layered cyclone in Northwestern Atlantic (see paragraph P2). Chances for the next African tropical wave to develop have diminshed (see paragraph P11).

...ATMOSPHERIC FEATURES BIRDSEYE CHART...

This chart is generated based on surface analysis from the National Hurricane Center TAFB at 1800Z, and the 1923Z-released HPC analysis.

In light blue is upper air analysis, with 200 mb wind barbs calculated by GOES satellite imagery showing the upper-level wind direction. Based on the 200 mb wind barbs, blue-dashed lines are locations of upper troughs, blue-zig-zag lines are locations of upper ridges. Blue Ls are locations of upper lows, blue Hs are locations of upper ridges.

In red is surface analysis, with solid lines indicating locations of surface fronts, dashed lines indicating locations of surface troughs, and zig-zag lines indicating surface ridge axes. Ls indicate surface lows, Hs indicate surface highs.

...THERMODYNAMICS BIRDSEYE CHART...

This chart is generated using GOES water vapor satellite imagery. Brown indicates dry air. White, blue, and purple indicates moist air. An increase in moisture indicates slower air parcel lapse rates with elevation and hence an increase toward instability.

Sea-surface temperatures are overlaid with light blue isotherms. The 26 deg C isotherm is highlighted in red. Waters at and south of the 26 deg C isotherm indicate low-level warmth and hence faster environmental lapse rates with elevation (more instability). Waters north of the 26 deg C isotherm indicate slower environmental lapse rates with elevation (less instability).

...MID-LATITUDES DISCUSSION...
P1...Strong upper ridge over North America has weakened due to cool air advection behind NW Atlantic cyclone in paragraph P2. Westerly warm air advection south of the same cyclone has spread this upper ridge eastward into the western Atlantic. Upper convergence on the south side of this upper ridge supports a 1018 mb surface ridge in the Gulf of Mexico.

P2...Northwest Atlantic surface cyclone remains centered over eastern Canada with surface center of 992 mb as of 1923Z. Now that the surface center has whirled beneath the less divergent core of its supporting upper vortex (which has recently opened into a longwave upper trough)...expect the surface center to begin weakening. Upper convergence behind the longwave upper trough supports a 1024 mb surface ridge in NE North Dakota. Split flow upper divergence between the SW edge of the longwave upper trough and north edge of the upper ridge in paragraph P1 supports t-storms...a long surface front...and frontal depressions across the east half of the US...all trailing from the surface cyclone. If this trailing front and t-storm activity sags southward into the favorable low shear/enhanced outflow of the upper ridge in paragraph P1...then tropical development in the norhwest Atlantic could be possible in the next days.

P3...NE Atlantic upper trough persists. Cut-off upper trough in the middle of the Atlantic left behind by this system has re-merged with it.

P4...Open Atlantic surface ridge still has a strong center...currently just west of the Azores...which is supported by upper convergence on the back side of the NE Atlantic upper trough (paragraph P3).

...TROPICAL BELT DISCUSSION...
P5...Central America upper ridge persits. T-storm activity supported by the outflow of this upper ridge has reduced now that the tropical wave in paragraph P9 has exited into the eastern Pacific.

P6...Caribbean upper vorticity has elongated into a few features while wedged between the Central America upper ridge in paragraph P5...eastern Caribbean upper ridge in paragraph P7...and North America upper ridge in paragraph P1. This upper vorticity now consists of an upper low in the southern Gulf of Mexico...an upper trough over the Bahamas...with split flow divergence at the boundary between these two features supporting a new surface trough/t-storms near south Florida. This upper vorticity also has an upper vortex in the south Caribbean...and yet another upper vortex south of Bermuda.

P7...Eastern Caribbean upper ridge persists with an anticyclonic center just northeast of the area.

P8...Expansive east Atlantic upper ridge continues. In conjunction with the surface ridge in paragraph P4...deep-layered easterly flow exists across much of the Atlantic tropics that is advecting African desert dry air (brown shading in the above thermo birdseye chart) westward. Single inverted upper trough on the south side of this upper ridge persists.

P9...Tropical wave crossing the southern Gulf of Mexico and Bay of Campeche in the previous discussion is now exiting the picture while moving into SE Mexico and eastern Pacific. Therefore...this is the last discussion of this tropical wave on this blog.

P10...Tropical wave approaching the northern Caribbean islands in the previous discussion is currently crossing Puerto Rico and the waters to the north. It remains suppressed by dry air mentioned in paragraph P8...and is encountering additional unfavorable conditions thanks to westerly vertical shear from the upper vorticity in paragraph P6.

P11...Tropical wave east of the Cape Verde Islands in the previous discussion has now crossed the islands...and is now just west of the islands. It is rolling into dry air mentioned in paragraph P8. It has failed to sustain enough t-storm activity to expand the east end of the upper ridge in paragraph P8 with latent heat release. Had it been able to do so...the tropical wave would have pushed off the inverted upper trough to the west such that the inverted trough would act as an enhanced outflow channel. It is now also entering the unfavorable upper convergent environment directly below this inverted upper trough.

Updated: 3:30 AM GMT on July 10, 2012

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2012 Atlantic Hurricane Season Birdseye Discussion #46

By: NCHurricane2009, 7:51 PM GMT on July 08, 2012

...JULY 8 2012...4:00 PM EDT...
Caribbean tropical wave still not expected to develop as it moves into the southern Gulf of Mexico (see paragraph P9 for details). Still Watching thunderstorm activity midway between New Jersey and Bermuda...associated with deep-layered cyclone in Northwestern Atlantic (see latter half of paragraph P2). Also still watching the next strong tropical wave emerging from west coast of Africa (see paragraph P11 for details).

...ATMOSPHERIC FEATURES BIRDSEYE CHART...

This chart is generated based on surface analysis from the National Hurricane Center TAFB at 0600Z, and the 0727Z-released HPC analysis.

In light blue is upper air analysis, with 200 mb wind barbs calculated by GOES satellite imagery showing the upper-level wind direction. Based on the 200 mb wind barbs, blue-dashed lines are locations of upper troughs, blue-zig-zag lines are locations of upper ridges. Blue Ls are locations of upper lows, blue Hs are locations of upper ridges.

In red is surface analysis, with solid lines indicating locations of surface fronts, dashed lines indicating locations of surface troughs, and zig-zag lines indicating surface ridge axes. Ls indicate surface lows, Hs indicate surface highs.

...THERMODYNAMICS BIRDSEYE CHART...

This chart is generated using GOES water vapor satellite imagery. Brown indicates dry air. White, blue, and purple indicates moist air. An increase in moisture indicates slower air parcel lapse rates with elevation and hence an increase toward instability.

Sea-surface temperatures are overlaid with light blue isotherms. The 26 deg C isotherm is highlighted in red. Waters at and south of the 26 deg C isotherm indicate low-level warmth and hence faster environmental lapse rates with elevation (more instability). Waters north of the 26 deg C isotherm indicate slower environmental lapse rates with elevation (less instability).

...MID-LATITUDES DISCUSSION...
P1...Strong upper ridge continues over North America...caused by the hot and parched lands over large areas of the United States. While continuing to zoom east across the north side of the upper ridge...eastern Canada frontal cyclone has become part of a large northwestern Atlantic cyclone (see paragraph P2 for details). Westerly advection south of the northwestern Atlantic cyclone has spread this upper ridge eastward into the western Atlantic. Upper convergence on the east side of this upper ridge supports a 1019 mb surface ridge in the eastern Gulf of Mexico.

P2...Deep-layered cyclone in northwest Atlantic has merged with eastern Canada frontal cyclone from paragraph P1...resulting in an intensifying 993 mb surface center over east Canada supported by divergence east of a large upper vortex...with upper convergence behind the upper vortex supporting a 1026 mb surface ridge just NE of Montana. Remainder of the cyclone's upper trough has merged with NE Atlantic upper troughing in paragaraph P3....and associated surface cyclone moving across Greenland is dissipating with a 1020 mb center SE of Greenland. 1012 mb frontal depression midway between New Jersey and Bermuda dissipated in last 36 hours...but t-storm flare ups continue in the area supported by split flow upper divergence at the boundary between the deep-layered cyclone and North America upper ridge in paragraph P1. A 1008 mb frontal depression is also entering this area from New Jersey after being over southern Minnesota in paragraph P1 of the previous discussion. With t-storms continuing and another frontal depression entering the area...still watching the northwestern Atlantic for slight chance of tropical development...although northerly shear from the upper ridge in paragraph P1 numbs development potential in this area.

P3...Frontal system pushing into western Europe leaves behind upper trough in NE Atlantic. Cut-off upper vortex west of the Azores (paragraph P4 of previous discussion) has merged with this upper trough. Cut-off upper trough in the middle of the Atlantic left behind by this system persists...wedged between the east Caribbean upper ridge in paragraph P7 and east Atlantic upper ridge in paragraph P8.

P4...Open Atlantic surface ridge still has a strong center...currently just north of the Azores...which is supported by upper convergence on the back side of the NE Atlantic upper trough (paragraph P3).

...TROPICAL BELT DISCUSSION...
P5...Central America upper ridge persits. Tropical wave in paragraph P9 continues to enhance t-storms caused by outflow of this upper ridge...and latent heat release from these t-storm clouds also is assisting this upper ridge.

P6...Caribbean upper vorticity is elongated east-west while wedged between the Central America upper ridge in paragraph P5...eastern Caribbean upper ridge in paragraph P7...and North America upper ridge in paragraph P1. This upper vorticity has been stretched into the eastern Caribbean...southern Gulf of Mexico...and western Atlantic south of Bermuda.

P7...Eastern Caribbean upper ridge persists with an anticyclonic center over the Virgin Islands.

P8...Expansive east Atlantic upper ridge continues. In conjunction with the surface ridge in paragraph P4...deep-layered easterly flow exists across much of the Atlantic tropics that is advecting African desert dry air (brown shading in the above thermo birdseye chart) westward. Inverted upper trough signatures on the south side of this upper ridge have consolidated into a single inverted upper trough located west of the tropical wave in paragraph P11.

P9...Tropical wave crossing Central America and the western Caribbean in the previous discussion is currently over Guatemala and the Yucatan...getting ready to enter the southern Gulf of Mexico and Bay of Campeche. The southern section of the tropical wave continues enhancing t-storm activity beneath a divergent Central America upper ridge (paragraph P5). While such a mechanism normally favors tropical development...land interaction with Central America has stopped this from happening. Meanwhile...northern end of this tropical wave is suppressed by strong westerly shear on the south side of the upper vorticity in paragraph P6.

P10...Tropical wave midway between the Cape Verde Islands and Lesser Antilles in the previous discussion is currently approaching the Lesser Antilles and northern Caribbean islands. It remains suppressed by dry air mentioned in paragraph P8. NHC TAFB analysis has been analyzing a 1013 mb surface low in the ITCZ located SE of the tropical wave...which I surmise is a southern fragment of this tropical wave left behind.

P11...Next strong tropical wave has emerged from the west coast of Africa...and is currently just east of the Cape Verde Islands. If the tropical wave in paragraph P10 is a good analogue...then dry air should ultimately prevent this wave from developing. However...I am still watching how this tropical wave is phasing with the inverted upper troughs on the south and east sides of the east Atlantic upper ridge (see latter half of paragraph P8). In particular...it is getting enhanced outflow from an inverted upper trough to its west...giving it a better chance to fight against the dry air that lies ahead. Of final note...this tropical wave lost its enhanced poleward outflow as the cut-off upper vortex W of the Canary Islands has been absorbed by the NE Atlantic upper troughing in pargraph P3. If this NE Atlantic upper troughing sags southward...enhanced poleward outflow could return to the tropical wave.

Updated: 3:32 AM GMT on July 10, 2012

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2012 Atlantic Hurricane Season Birdseye Discussion #45

By: NCHurricane2009, 5:58 AM GMT on July 07, 2012

...JULY 7 2012...2:05 AM EDT...
Caribbean tropical wave still not expected to develop as it heads toward Gulf of Mexico (see paragraph P11 for details). Watching frontal boundary low midway between New Jersey and Bermuda...attached to deep-layered cyclone in Northwestern Atlantic (paragraph P2). Unlike the recent string of tropical waves...next strong tropical wave emerging from west coast of Africa may have a better chance to develop (see paragraph P13 for details).

...ATMOSPHERIC FEATURES BIRDSEYE CHART...

This chart is generated based on surface analysis from the National Hurricane Center TAFB at 0000Z, and the 0138Z-released HPC analysis.

In light blue is upper air analysis, with 200 mb wind barbs calculated by GOES satellite imagery showing the upper-level wind direction. Based on the 200 mb wind barbs, blue-dashed lines are locations of upper troughs, blue-zig-zag lines are locations of upper ridges. Blue Ls are locations of upper lows, blue Hs are locations of upper ridges.

In red is surface analysis, with solid lines indicating locations of surface fronts, dashed lines indicating locations of surface troughs, and zig-zag lines indicating surface ridge axes. Ls indicate surface lows, Hs indicate surface highs.

...THERMODYNAMICS BIRDSEYE CHART...

This chart is generated using GOES water vapor satellite imagery. Brown indicates dry air. White, blue, and purple indicates moist air. An increase in moisture indicates slower air parcel lapse rates with elevation and hence an increase toward instability.

Sea-surface temperatures are overlaid with light blue isotherms. The 26 deg C isotherm is highlighted in red. Waters at and south of the 26 deg C isotherm indicate low-level warmth and hence faster environmental lapse rates with elevation (more instability). Waters north of the 26 deg C isotherm indicate slower environmental lapse rates with elevation (less instability).

...MID-LATITUDES DISCUSSION...
P1...Strong upper ridge continues over North America...caused by the hot and parched lands over large areas of the United States. Cut-off upper trough over the SE US coast continued southward while orbiting this upper ridge...and has merged with upper vorticity in paragraph P8. While continuing to zoom east across the north side of the upper ridge...south-central Canada frontal cyclone and its upper trough now has a 998 mb surface center as it moves into eastern Canada. The cold front trailing from this Canadian cyclone features a 1009 mb depression now over southern Minnesota...supported by accelerational upper divergence of a strong westerly jet on the north side of this upper ridge. Finally...upper divergence at the boundary between this upper ridge and upper vorticity in paragraph P8 has weakened the SE US and Gulf of Mexico surface ridge...and also has supported t-storms across the SE US and US Gulf coast.

P2...Deep-layered cyclone in northwest Atlantic has weakened from 1000 to 1002 mb in last 12 hours..and continues moving northward around the surface ridge in paragraph P5...toward Atlantic Canada and toward waters temps in the teens of deg C too cool for subtropical development. Remainder of the deep-layered cyclone's upper trough is moving across Greenland with the relatively new surface cyclone it supports. Attached to the cold front of the deep-layered cyclone is a weak 1012 mb low and associated t-storms midway between New Jersey and Bermuda...supported by split flow upper divergence at the boundary between the deep-layered cyclone and North America upper ridge in paragraph P1. This 1012 mb low is tracking ESE around the deep-layered cyclone...and I believe it has a slight chance of tropical development as it passes over or just north of Bermuda. The only unfavorable factor for its tropical development at this hour is northerly wind shear induced by the North America upper ridge in paragraph P1.

P3...Frontal system pushing into western Europe is marked with upper trough and extratropical surface low in the upper-right corner of the above charts. Cut-off upper trough in the middle of the Atlantic left behind by this system is now an upper low...wedged between the east Caribbean upper ridge in paragraph P9 and east Atlantic upper ridge in paragraph P10.

P4...Cut-off upper vortex west of the Azores appears to be merging with the southwest end of the upper troughing of the system in paragraph P3.

P5...Open Atlantic surface ridge still has a strong center....currently just north of the Azores...which is supported by upper convergence on the back side of the upper troughing pushing into Europe (paragraph P3).

...TROPICAL BELT DISCUSSION...
P6...Inverted upper trough over the Bay of Campeche and western Gulf of Mexico has retrograding slowly west into south Texas and NE Mexico while orbiting the strong central North America upper ridge mentioned in paragraph P1.

P7...Anticyclonic upper ridge over Central America continues to be centered near the Panama area. Surface convergence from the tropical wave in paragraph P11...coupled with upper divergence supplied by this upper ridge...continues to enhance the Panama area t-storm activity.

P8...Caribbean upper vorticity is elongated east-west while wedged between the Central America upper ridge in paragraph P7...eastern Caribbean upper ridge in paragraph P9...and North America upper ridge in paragraph P1. As the upper ridge in paragraph P7 has grown...a fragment of this upper vorticity has become split off into the eastern Caribbean. The remainder of this upper vorticity is retrograding westward into the southern Gulf of Mexico...about the strong upper ridge in paragraph P1.

P9...Eastern Caribbean upper ridge persists with an anticyclonic center just northeast of this area.

P10...Expansive east Atlantic upper ridge continues. In conjunction with the surface ridge in paragraph P5...deep-layered easterly flow exists across much of the Atlantic tropics that is advecting African desert dry air (brown shading in the above thermo birdseye chart) westward. Inverted upper trough signatures on the south and east sides of this east Atlantic upper ridge continue...one of which has closed off into an upper low W of the Canary Islands that could retrograde southwestward around the upper ridge in the next days...or alternatively get absorbed by upper troughing currently pushing into Europe (paragraph P3).

P11...Tropical wave crossing the central Caribbean in the previous discussion is now crossing central America and the western Caribbean. The center section of the tropical wave is suppressed by upper vorticity in paragraph P8. The southern section is enhancing t-storm activity beneath a divergent Central America upper ridge (paragraph P7). I see the southern section as the only development potential with this wave...especially as the paragraph P7 upper ridge expands in the wake of gradually collapsing paragraph P8 upper vorticity...and also expands with latent heat release of those t-storm clouds. However...this t-storm activity is about to make landfall in central America (Nicaragua and Costa Rica). Finally...northern end of this tropical wave is producing t-storms over eastern Cuba and eastern Bahamas...enhanced by upper divergence between paragraph P8 upper vorticity and paragraph P9 upper ridge. Although shear is low in the Gulf of Mexico (thanks to deep-layered easterlies on the south side of the upper ridge and Gulf of Mexico surface ridge in paragraph P1)...I expect the northern end of this tropical wave to lose its t-storm activity while becoming suppressed by upper convergence directly beneath the paragraph P8 upper vorticity.

P12...Tropical wave midway between the Cape Verde Islands and Lesser Antilles remains suppressed by dry air mentioned in paragraph P10.

P13...Satellite imagery suggests the next strong tropical wave is about to emerge from the west coast of Africa (as remarked in the lower-right corner of the above charts). If the tropical wave in paragraph P12 is a good analogue...then dry air should ultimately prevent this wave from developing. However...I am watching how this tropical wave is phasing with the inverted upper troughs on the south and east sides of the east Atlantic upper ridge (see latter half of paragraph P10). In particular...it has opportunity to get enhanced outflow from an inverted upper trough to its west...and cut-off upper low to its north located west of the Canary Islands (especially if that cut-off upper low retrogrades southwestward). If such upper outflow enhancement occurs...the tropical wave stands a chance to fight off dry air unlike its recent predecessors.

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2012 Atlantic Hurricane Season Birdseye Discussion #44

By: NCHurricane2009, 6:07 PM GMT on July 06, 2012

...JULY 6 2012...2:15 PM EDT...
Eastern Caribbean tropical wave still not expected to develop (see paragraph P10 for details). Northwestern Atlantic disturbance has been absorbed by deep-layered 1000 mb cyclone (paragraph P1). Next strong tropical wave is emerging from west coast of Africa (paragraph P12).

...ATMOSPHERIC FEATURES BIRDSEYE CHART...

This chart is generated based on surface analysis from the National Hurricane Center TAFB at 1200Z, and the 1334Z-released HPC analysis.

In light blue is upper air analysis, with 200 mb wind barbs calculated by GOES satellite imagery showing the upper-level wind direction. Based on the 200 mb wind barbs, blue-dashed lines are locations of upper troughs, blue-zig-zag lines are locations of upper ridges. Blue Ls are locations of upper lows, blue Hs are locations of upper ridges.

In red is surface analysis, with solid lines indicating locations of surface fronts, dashed lines indicating locations of surface troughs, and zig-zag lines indicating surface ridge axes. Ls indicate surface lows, Hs indicate surface highs.

...THERMODYNAMICS BIRDSEYE CHART...

This chart is generated using GOES water vapor satellite imagery. Brown indicates dry air. White, blue, and purple indicates moist air. An increase in moisture indicates slower air parcel lapse rates with elevation and hence an increase toward instability.

Sea-surface temperatures are overlaid with light blue isotherms. The 26 deg C isotherm is highlighted in red. Waters at and south of the 26 deg C isotherm indicate low-level warmth and hence faster environmental lapse rates with elevation (more instability). Waters north of the 26 deg C isotherm indicate slower environmental lapse rates with elevation (less instability).

...MID-LATITUDES DISCUSSION...
P1...While continuing eastward around the central North America upper ridge...diffuse 1002 mb cyclone over the NE US has moved into the northwest Atlantic as a deep-layered 1000 mb cyclone...and this deep-layered cyclone is moving northward around the surface ridge in paragraph P4...hence tracking toward Atlantic Canada and toward waters temps in the teens of deg C too cool for subtropical development. Remainder of the deep-layered cyclone's upper trough is moving toward the west coast of Greenland with a new 1008 mb cyclone it supports. Cut-off upper trough over the Tennesee valley has moved southward over the SE US coast while orbiting the central North America upper ridge. While continuing to zoom east across the north side of the upper ridge...south-central Canada frontal cyclone and its upper trough now has a 997 mb surface center over E Hudson Bay. The cold front trailing from this south-central Canadian cyclone features a 1008 mb depression and t-storm complex supported by upper divergence on the NW quadrant of the upper ridge. Finally...upper convergence on the east side of the upper ridge is supporting the 1018 mb ridge in the eastern Gulf of Mexico and SE US.

P2...Complex frontal system covering the northern half of the Atlantic Ocean has all made landfall in western Europe (marked with upper trough and extratropical surface low in the upper-right corner of the above charts). It left behind a west Atlantic upper trough 24 hrs ago that was getting absorbed by the upper-layers of the deep-layered 1000 mb cyclone in paragraph P1. Whatever did not get absorbed is now a cut-off upper trough in the middle of the Atlantic...wedged between the east Caribbean upper ridge in paragraph P8 and east Atlantic upper ridge in paragraph P9.

P3...Cut-off upper vortex southwest of the Azores has moved northward toward upper troughing of the system in paragraph P2...and is now west of the Azores.

P4...Open Atlantic surface ridge still has a strong center....currently just north of the Azores...which is supported by upper convergence on the back side of the upper troughing pushing into Europe (paragraph P2).

...TROPICAL BELT DISCUSSION...
P5...Inverted upper trough over the Bay of Campeche and western Gulf of Mexico is retrograding slowly west into south Texas and NE Mexico while orbiting the strong central North America upper ridge mentioned in paragraph P1.

P6...Upper ridge over Central America has gained concentration near the Panama area...where t-storm activity and associated latent heat release has been strongest in the last 24 hours. Surface convergence from the tropical wave in paragraph P10 may be enhancing the Panama area t-storm activity.

P7...Central Caribbean upper vorticity has gained east-west stretch while wedged between the Central America upper ridge in paragraph P6...eastern Caribbean upper ridge in paragraph P8...and North America upper ridge in paragraph P1.

P8...Eastern Caribbean upper anticyclonic ridge persists. Its upper outflow had supported extensive t-storm activity for the tropical wave in paragraph P10 24 hours ago...which has since left the area. The remnant debris clouds of this t-storm activity are now anticyclonically turning about this upper ridge.

P9...Expansive east Atlantic upper ridge continues. In conjunction with the surface ridge in paragraph P4...deep-layered easterly flow exists across much of the Atlantic tropics that is advecting African desert dry air (brown shading in the above thermo birdseye chart) westward. Inverted upper trough signatures on the south and east sides of this east Atlantic upper ridge continue...one of which has closed off into an upper low W of the Canary Islands that could retrograde southwestward around the upper ridge in the next days...or altenratively get absorbed by upper troughing currently pushing into Europe (paragraph P2).

P10...Tropical wave crossing the eastern Caribbean in the previous discussion is now in the central Caribbean. As expected...the tropical wave has finally become suppressed by upper vorticity in paragraph P7. The only development potential I see is near the Panama area...where the tropical wave is enhancing t-storm activity beneath a divergent Central America upper ridge (paragraph P6)...especially if that upper ridge expands in the wake of gradually collapsing upper vorticity in paragraph P7. Not seeing signs of this occurring at this time. Although shear is low in the Gulf of Mexico...thanks to deep-layered easterlies on the south side of the upper ridge and 1018 mb surface ridge in paragraph P1...a look at the models shows the upper vorticity in paragraph P7 retrograding westward into the Gulf of Mexico...and therefore I expect the tropical wave to remain suppressed by upper convergence beneath this upper vorticity as the tropical wave continues toward the Gulf of Mexico.

P11...Tropical wave west of the Cape Verde Islands in the previous discussion is now midway between the Cape Verdes and Lesser Antilles. This tropical wave is in favorable low shear thanks to deep-layered easterly flow mentioned in paragaraph P9...but is suppressed by dry air also mentioned in paragraph P9.

P12...Satellite imagery suggests the next strong tropical wave is about to emerge from the west coast of Africa (as remarked in the lower-right corner of the above charts). If the tropical wave in paragraph P11 is a good analogue...then dry air should ultimately prevent this wave from developing. However...I am watching how this tropical wave phases with new upper low located west of the Canary Islands...mentioned towards the end of paragraph P9. If this upper low retrogrades southwestward...then it could enhance the poleward upper outflow of this tropical wave...allowing it to fight against the dry air.

Updated: 3:36 AM GMT on July 10, 2012

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2012 Atlantic Hurricane Season Birdseye Discussion #43

By: NCHurricane2009, 11:05 AM GMT on July 05, 2012

...JULY 5 2012...7:10 AM EDT...
Concerning latest information on eastern Caribbean tropical wave in special update #42A...see paragraph P11.

Disturbed weather offshore of the northeastern United States and north of Bermuda...also in special update #42A...has been upgraded to a special feature on this blog in case it surprises us. See the special feature section for more details on this situation.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...

This chart is generated based on surface analysis from the National Hurricane Center TAFB at 0600Z, and the 0811Z-released HPC analysis.

In light blue is upper air analysis, with 200 mb wind barbs calculated by GOES satellite imagery showing the upper-level wind direction. Based on the 200 mb wind barbs, blue-dashed lines are locations of upper troughs, blue-zig-zag lines are locations of upper ridges. Blue Ls are locations of upper lows, blue Hs are locations of upper ridges.

In red is surface analysis, with solid lines indicating locations of surface fronts, dashed lines indicating locations of surface troughs, and zig-zag lines indicating surface ridge axes. Ls indicate surface lows, Hs indicate surface highs.

...THERMODYNAMICS BIRDSEYE CHART...

This chart is generated using GOES water vapor satellite imagery. Brown indicates dry air. White, blue, and purple indicates moist air. An increase in moisture indicates slower air parcel lapse rates with elevation and hence an increase toward instability.

Sea-surface temperatures are overlaid with light blue isotherms. The 26 deg C isotherm is highlighted in red. Waters at and south of the 26 deg C isotherm indicate low-level warmth and hence faster environmental lapse rates with elevation (more instability). Waters north of the 26 deg C isotherm indicate slower environmental lapse rates with elevation (less instability).

...SPECIAL FEATURE...NORTHWESTERN ATLANTIC DISTURBANCE...
This disturbance is currently north of Bermuda and east of the northeastern US coast...moving due east amongst westerly flow on the north side of surface ridges mentioned in paragraphs P1 and P5. As mentioned in special update #42A...this disturbance formed along the surface warm front of what is now the 1002 mb NE US cyclone mentioned in paragraph P1. Warm air advection from the 1002 mb cyclone amplified the eastern lobe of the upper ridge in paragraph P1 such that it aligned with the warm front and enhanced upper outflow similar to a tropical cyclone's structure. Recently...the warm front has been downgraded to a surface trough (suggesting more tropical characteristics in the area with air mass contrasts diminishing).

Looking ahead..conditions are expected to become less favorable as this disturbance continues eastward away from the 26 deg C Gulf stream waters. Moreover...the favorable lobe of upper ridging looks to get squeezed out as the NE US 1002 mb cyclone's upper trough merges with a west Atlantic upper trough (end of paragraph P2). But because the disturbance still has a good spin and abundant t-storm activity on satellite animations...it may suprise us by becoming upgraded to a short-lived tropical cyclone before then...if not at least an area of interest in the NHC Tropical Weather Outlook or an Invest on the NRL (Naval Research Laboratory) site. That is why I have upgraded it to a special feature on this blog.

...MID-LATITUDES DISCUSSION...
P1...While moving eastward across the central North America upper ridge...southern Hudson Bay frontal system anchored by 998 mb center 24 hrs ago has arrived to the northeastern United States with a diffuse 1002 mb center...and its supporting upper trough follows behind. Convergence on the back side of this upper trough supports a 1013 to 1014 mb ridge over eastern Hudson Bay. This upper trough also left behind a cut-off upper low over the Tenessee valley 24 hrs ago which has since weakened to an upper trough in the midst of the strong central North America upper ridge. A second upper trough and frontal system from SW Canada is now over south-central Canada while continuing to zoom east across the north side of the central North America upper ridge. Upper convergence on the east side of this upper ridge is supporting the 1018 mb ridge in the eastern Gulf of Mexico...which extends to a 1022 mb center E of Bermuda.

P2...Complex frontal system covering the northern half of the Atlantic Ocean persists. A frontal cyclone and its supporting upper trough has made landfall in western Europe (marked as an extratropical low in the upper-right of the above charts). What is now a 1010 mb frontal cyclone speeding eastward to Europe was a diffuse cyclone over E Canada 24 hrs ago. It has left behind its supporting upper trough over the western Atlantic...carving out its own shortwave upper trough with cool air advection as it heads toward Europe. Meanwhile...the residual west Atlantic upper trough will be merging with the upper trough of the 1002 mb northeastern US cyclone mentioned in paragraph P1.

P3...Upper ridge over Greenland and the high seas south of Greenland is de-amplifying as it get squeezed out in between the 1010 mb cyclone's upper trough and western Atlantic upper trough...both upper troughs mentioned in paragraph P2 above.

P4...Cut-off upper vortex southwest of the Azores continues to shift westward while retrograding about the upper ridge in paragraph P3. The surface trough it once supported has moved westward while steered by strong surface ridge mentioned in paragraph P5. Surface trough is visible on satellite as a faint swirl of clouds.

P5...Open Atlantic surface ridge still has a strong center....currently just north of the Azores...which is supported by upper convergence on the back side of the upper troughs/surface frontal cyclones currently pushing into Europe (paragraph P2).

...TROPICAL BELT DISCUSSION...
P6...Inverted upper trough over the Bay of Campeche and western Gulf of Mexico is retrograding slowly west into Texas and NE Mexico while orbiting the strong central North America upper ridge mentioned in paragraph P1.

P7...Upper ridge over Central America is enhancing upper outflow for t-storm activity across the region. Surface convergence from a tropical wave (formerly Invest 97-L) is also be enhancing this activity. As mentioned here yesterday...it looks as though this system will shift westward into the eastern Pacific and potentially develop there.

P8...Central Caribbean upper vorticity has spilt off from western Atlantic upper trough (paragraph P2) after merging with it yesterday. Split is due to strength of central North America upper ridge. This upper vorticity has an upper vortex spinning over the east Bahamas and east Cuba.

P9...Eastern Caribbean upper anticyclone persists.

P10...Expansive east Atlantic upper ridge continues...featuring an anticyclonic center SE of the Azores. In conjunction with the surface ridge in paragraph P5...deep-layered easterly flow exists across much of the Atlantic tropics that is advecting African desert dry air (brown shading in the above thermo birdseye chart) westward. Inverted upper trough signatures on the south and east sides of this east Atlantic upper ridge continue.

P11...Tropical wave crossing the Lesser Antilles in the previous discussion is moving across the eastern Caribbean today...and this morning's 0600Z TAFB position places it across Puerto Rico. The upper outflow produced by the east Caribbean upper ridge (paragraph P9) has allowed the tropical wave to see a good increase in its t-storm activity in the past 24 hours. It also briefly became an area of interest in the NHC Tropical Weather Outlook thanks to gusty winds measured over the Virgin Islands. In the short-term...the t-storm activity of the tropical wave looks to move over Hispaniola (Haiti and the Domincan Republcic). After that...the tropical wave looks to get sheared by central Caribbean upper vorticity (paragraph P8)...which is why it is still not expected to develop.

P12...Strong tropical wave SE of the Cape Verde Islands in the previous discussion is now west of those islands this morning. This tropical wave is also in favorable low shear thanks to deep-layered easterly flow mentioned in paragaraph P10...but is rolling into the dry air also mentioned in paragraph P10...and therefore I do not expect it to develop in the next days.

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2012 Atlantic Hurricane Season Birdseye Discussion #42A (Special Update)

By: NCHurricane2009, 7:24 PM GMT on July 04, 2012

...JULY 4 2012...3:25 PM EDT...
Two areas of interest have quickly popped up on this 4th of July. One is located over the Lesser Antilles...Virgin Islands...Puerto Rico...and eastern Caribbean Sea...associated with the tropical wave in full discussion #42 paragraph P11. The second is located offshore of the northeastern United States...associated with southern Hudson Bay frontal cyclone mentioned in paragraph P1 of full discussion #42. Both pop up areas of interest and their surrounding environment are shown in Figure 1.


Figure 1: Two pop-up areas of interest this afternoon and their surrounding environment. Paragraph numbers are associated with full discussion #42.

Cocerning the eastern Caribbean tropical wave (full discussion #42...paragraph P11)...the National Hurricane Center introduced it into their tropical weather outlook this afternoon because of gusty winds measured over the Virgin Islands. This re-enforces the vigor of the tropical wave...but the National Hurricane Center gives it a 0% chance of developing in the next 48 hours. While it is currently under a favorable east Caribbean upper ridge (paragraph P9...discussion #42) that is enhancing its upper outflow...the tropical wave is not producing enough storm activity & associated latent heat release to expand the size of this upper ridge. Therefore...I too still expect no development with this tropical wave as it encounters unfavorable westerly vertical shear associated with central Caribbean upper vorticity (as shown in Figure 1 above).

Concerning the quickly growing cluster of thunderstorms offshore of the northeastern United States...this is associated with the warm front of the southern Hudson Bay frontal cyclone mentioned in paragraph P1 of discussion #42. This area of disturbed weather should move east away from land while located amongst westerly flow on the north side of the open Atlantic ridge (paragraph P5...discussion #42). Because warm air advection ahead of the Hudson Bay frontal cyclone has amplified central North American upper ridging over the warm front and disturbed weather (as shown in Figure 1)...I believe this has a better chance of developing than the eastern Caribbean tropical wave...especially if the upper ridge axis stays aligned with the disturbed weather such that it continues to enhance its upper outflow similar to a tropical cyclone. Water temps over the south half of the disturbance are at or above 26 deg C...sufficiently warm for tropical development. Meanwhile...the Tennessee Valley cut-off upper low and surface trough it is supporting...also left behind by this Hudson Bay frontal cyclone...shows only widely scattered t-storms across the SE United States on radar.

Return to full discussion #42 for current situation across the rest of the Atlantic tropics.

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2012 Atlantic Hurricane Season Birdseye Discussion #42

By: NCHurricane2009, 2:29 PM GMT on July 04, 2012

...JULY 4 2012...10:30 AM EDT...
Atlantic tropics remain calm.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...
This chart is generated based on surface analysis from the National Hurricane Center TAFB at 0000Z, and the 0127Z-released HPC analysis.

In light blue is upper air analysis, with 200 mb wind barbs calculated by GOES satellite imagery showing the upper-level wind direction. Based on the 200 mb wind barbs, blue-dashed lines are locations of upper troughs, blue-zig-zag lines are locations of upper ridges. Blue Ls are locations of upper lows, blue Hs are locations of upper ridges.

In red is surface analysis, with solid lines indicating locations of surface fronts, dashed lines indicating locations of surface troughs, and zig-zag lines indicating surface ridge axes. Ls indicate surface lows, Hs indicate surface highs.

...THERMODYNAMICS BIRDSEYE CHART...

This chart is generated using GOES water vapor satellite imagery. Brown indicates dry air. White, blue, and purple indicates moist air. An increase in moisture indicates slower air parcel lapse rates with elevation and hence an increase toward instability.

Sea-surface temperatures are overlaid with light blue isotherms. The 26 deg C isotherm is highlighted in red. Waters at and south of the 26 deg C isotherm indicate low-level warmth and hence faster environmental lapse rates with elevation (more instability). Waters north of the 26 deg C isotherm indicate slower environmental lapse rates with elevation (less instability).

...MID-LATITUDES DISCUSSION...
P1...While moving eastward across the central North America upper ridge...frontal system anchored by 1001 mb center in NE Manitoba 24 hrs ago has translated across the southern Hudson Bay with a 998 mb center...and its supporting upper trough follows behind. The supporting upper trough has left behind a cut-off upper low over the Tenessee valley wedged into the upper ridge...divergence E of this cut-off supporting a surface trough and t-storms over the Carolinas and Georgia. A second upper trough and frontal system is beginning to enter the picture from SW Canada while it too will zoom across the north side of the central North America upper ridge. Finally...upper convergence on the east side of this upper ridge is beginning to support the east Gulf of Mexico surface ridge (currently 1017 mb). This surface ridge was earlier supported by upper convergence on the back side of the upper troughing in paragraph P2.

P2...Complex frontal system covering the northwest half of the Atlantic Ocean persists. A frontal cyclone and its supporting upper trough is making landfall in western Europe (marked as an extratropical low in the upper-right of the above charts). A diffuse 1006 mb frontal cyclone and associated supporting upper trough is centered over eastern Canada coast. The cut-off upper trough over the Bahamas...as well as the cut-off upper vorticity in paragraph P8...have merged with the eastern Canada cyclone's upper trough.

P3...Upper ridge over Greenland and the high seas south of Greenland persists...supported by warm air advection ahead of E Canada cyclone mentioned in paragraph P2. It may soon re-merge with the upper anticyclone it left behind SE of the Azores (paragraph P10).

P4...Cut-off upper vortex south of the Azores (and the surface trough it is supporting) have shifted westward while retrograding about the upper ridge in paragraph P3. The surface trough is supported by split flow upper divergence between the NE edge of the upper vortex and NW edge of the upper anticyclone SE of the Azores (paragraph P10). Finally...cut-off upper trough E of Bermuda is merging with upper troughing of the complex frontal system in paragraph P2...but it leaves behind a cut-off upper trough NE of the Lesser Antilles wedge between the east Caribbean upper anticyclone (paragraph P9) and E Atlantic upper ridge (paragraph P10).

P5...Open Atlantic surface ridge still has a strong center....currently just NW of the Azores...which has strengthened as expected thanks to upper convergence on the back side of the upper trough/surface frontal cyclone currently pushing into Europe (paragraph P2).

...TROPICAL BELT DISCUSSION...
P6...Inverted upper trough over the Bay of Campeche and western Gulf of Mexico is jammed stationary in the southeastern armpit of the upper ridge mentioned in paragraph P1.

P7...Upper ridge over Central America is enhancing upper outflow for t-storm activity across the region...particularly over Panama where the flow around this upper ridge heavily diverges with the flow going into the central Caribbean upper vorticity (paragraph P8). Surface convergence from the Caribbean tropical wave (formerly Invest 97-L) may also be enhancing the Panama area activity. It is possible that the tropical wave enhances the disturbed Central America weather...then moves into the eastern Pacific and develops there instead.

P8...Central Caribbean upper vorticity has merged with E Canada cyclone's upper trough as remarked in paragraph P2.

P9...Eastern Caribbean upper anticyclone persists.

P10...Expansive east Atlantic upper ridge continues...and is still merging with upper anticyclone SE of the Azores mentioned in paragraph P3. In conjunction with the surface ridge in paragraph P5...deep-layered easterly flow exists across much of the Atlantic tropics that is advecting African desert dry air (brown shading in the above thermo birdseye chart) westward. Inverted upper trough signatures on the south and east sides of this east Atlantic upper ridge continue.

P11...Tropical wave nearing Lesser Antilles in the previous discussion is moving across these islands today. It was able to "punch out" some of the dry air (paragraph P10) in small areas thanks to split flow upper divergence on the west end of the east Atlantic upper ridge (paragraph P10). It is producing small areas of clouds and possible showers as it crosses the islnds...and may get aided by some of the upper outflow produced by the east Caribbean upper ridge (paragraph P9). After that...the tropical wave looks to get suppressed by central Caribbean upper vorticity (paragraph P8).

P12...Strong tropical that has recently rolled off of Africa is positioned SE of the Cape Verde Islands per this morning's 0000Z TAFB analysis. Disturbed weather southwest of the Cape Verde Islands (left behind by tropical wave in paragraph P11) appears to have dissipated thanks to dry air in paragraph P10...so this tropical wave can no longer absorb it. This tropical wave is also in favorable low shear thanks to deep-layered easterly flow mentioned in paragaraph P10...but may not develop if it struggles with the dry air also mentioned in paragraph P10.

Updated: 3:45 AM GMT on July 10, 2012

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2012 Atlantic Hurricane Season Birdseye Discussion #41

By: NCHurricane2009, 2:05 PM GMT on July 03, 2012

...JULY 3 2012...10:05 AM EDT...
Outside of vigorous tropical wave activity...none of which is organizing at this time...Atlantic tropics remain calm.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...

This chart is generated based on surface analysis from the National Hurricane Center TAFB at 0600Z, and the 0724Z-released HPC analysis.

In light blue is upper air analysis, with 200 mb wind barbs calculated by GOES satellite imagery showing the upper-level wind direction. Based on the 200 mb wind barbs, blue-dashed lines are locations of upper troughs, blue-zig-zag lines are locations of upper ridges. Blue Ls are locations of upper lows, blue Hs are locations of upper ridges.

In red is surface analysis, with solid lines indicating locations of surface fronts, dashed lines indicating locations of surface troughs, and zig-zag lines indicating surface ridge axes. Ls indicate surface lows, Hs indicate surface highs.

...THERMODYNAMICS BIRDSEYE CHART...

This chart is generated using GOES water vapor satellite imagery. Brown indicates dry air. White, blue, and purple indicates moist air. An increase in moisture indicates slower air parcel lapse rates with elevation and hence an increase toward instability.

Sea-surface temperatures are overlaid with light blue isotherms. The 26 deg C isotherm is highlighted in red. Waters at and south of the 26 deg C isotherm indicate low-level warmth and hence faster environmental lapse rates with elevation (more instability). Waters north of the 26 deg C isotherm indicate slower environmental lapse rates with elevation (less instability).

...MID-LATITUDES DISCUSSION...
P1...Frontal system anchored by 1003 mb center in western Dakotas now has a 1001 mb center in NE Manitoba...and its supporting upper trough follows behind. Warm air advection ahead of this frontal system supports a growing upper ridge over central North America which still has an anticyclonic center over NE New Mexico.

P2...Complex frontal system covering the northwest half of the discussion area (eastern North America and northern Atlantic) persists. A frontal cyclone and its supporting upper trough is making landfall in western Europe (marked as an extratropical low in the upper-right of the above charts). A 1004 mb frontal cyclone and associated supporting upper trough is centered over eastern Canada. Convergent back side of the upper troughing continues to support surface ridging....including a 1016 mb center in the NE Gulf of Mexico...1017 mb center over the SE US...and 1014 mb center over eastern Canada. Finally...Texas cut-off upper trough has dissipated in the face of strengthening upper ridge mentioned in paragraph P1...and this system has delivered yet another cut-off upper trough moving SE across the western Atlantic and Bahamas.

P3...Upper ridge over the Atlantic and south Greenland remains split in three areas by mass cool air advection behind the complex frontal system in paragraph P2 above. The northern part is an upper ridge over Greenland and the high seas south of Greenland. The middle part is an upper anticyclone in the open Atlantic currently SE of the Azores...and looks to become part of the east Atlantic upper ridge in paragraph P11 (and hence is moved to that paragraph of the tropical belt discussion). The southern part is an upper anticyclone still located in the eastern Caribbean...and hence has its own paragraph in the tropical belt discussion (see paragraph P10).

P4...Surface trough from old frontal boundary remains in the upper-right corner of the above charts toward southern Spain and northern Morocco. Cut-off upper vortex south of the Azores persists. Surface trough south of the Azores also persists...today supported by split flow upper divergence between the NE edge of the upper vortex and NW edge of the middle upper anticyclone mentioned in paragraph P3. Finally...cut-off upper trough E of Bermuda persists...but likely will merge with upper troughing of the complex frontal system in paragraph P2. The central Caribbean fragment of this cut-off upper trough remains stationary...and is moved to paragraph P9 of the tropical belt discussion.

P5...Open Atlantic surface ridge still has a strong center....which is now 1029 mb and SW of the Azores as of 0600Z TAFB. Expect it to regain strength as it becomes supported by upper convergence on the back side of the upper trough/surface frontal cyclone currently pushing into Europe (paragraph P2).

...TROPICAL BELT DISCUSSION...
P6...Upper ridge in the western Gulf of Mexico has merged with sprawling central North America upper ridge mentioned in paragraph P1.

P7...Inverted upper trough over the Yucatan and southern Gulf of Mexico has retrograded westward about the upper ridge in paragraph P1 and into the Bay of Campeche.

P8...Small upper ridge over Central America is enhancing upper outflow for t-storm activity across the region.

P9...Central Caribbean upper vorticity persists...originating as a cut-off from the weather system in paragraph P4.

P10...Eastern Caribbean upper anticyclone persists...originating as a cut-off from the decaying upper ridge mentioned in paragraph P3.

P11...Expansive east Atlantic upper ridge continues...and is merging with upper anticyclone SE of the Azores mentioned in paragraph P3. In conjunction with the surface ridge in paragraph P5...deep-layered easterly flow exists across much of the Atlantic tropics that is advecting African desert dry air (brown shading in the above thermo birdseye chart) westward. Three inverted upper troughs on the south side of this east Atlantic upper ridge show up today...but not sure what caused them at this hour.

P12...Tropical wave in the central Caribbean (formerly Invest 97-L) is becoming suppressed by central Caribbean upper vorticity mentioned in paragraph P9.

P13...Vigorous tropical wave midway between the Cape Verdes and Lesser Antilles in the previous discussion is moving closer to the Lesser Antilles. This tropical wave is struggling with the dry air mentioned in paragraph P11. However...it is producing a small area of rapidly moistening air east of the Lesser Antilles while getting help from split flow upper divergence located at the west end of the upper ridge mentioned in paragraph P11. More interesting...long-term satellite animation suggests that this tropical wave left behind a surface low pressure southwest of the Cape Verde Islands...whose signature is well-defined at this hour with a t-storm cluster in that area. Perhaps this surface low will get absorbed by the next tropical wave mentioned in paragraph P14.

P14...The next strong tropical wave has entered the tropical waters of the Atlantic from western Africa. As it continues westward...it may absorb disturbed weather southwest of the Cape Verde Islands (left behind by the tropical wave in paragraph P13). This tropical wave is also in favorable low shear thanks to deep-layered easterly flow mentioned in paragaraph P11...but may not develop if it struggles with the dry air also mentioned in paragraph P11.

Updated: 2:11 PM GMT on July 03, 2012

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2012 Atlantic Hurricane Season Birdseye Discussion #40

By: NCHurricane2009, 11:15 PM GMT on July 02, 2012

...JULY 2 2012...7:20 PM EDT...
Atlantic tropics remaining calm as the month of July begins.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...

This chart is generated based on surface analysis from the National Hurricane Center TAFB at 0000Z, and the 0123Z-released HPC analysis.

In light blue is upper air analysis, with 200 mb wind barbs calculated by GOES satellite imagery showing the upper-level wind direction. Based on the 200 mb wind barbs, blue-dashed lines are locations of upper troughs, blue-zig-zag lines are locations of upper ridges. Blue Ls are locations of upper lows, blue Hs are locations of upper ridges.

In red is surface analysis, with solid lines indicating locations of surface fronts, dashed lines indicating locations of surface troughs, and zig-zag lines indicating surface ridge axes. Ls indicate surface lows, Hs indicate surface highs.

...THERMODYNAMICS BIRDSEYE CHART...

This chart is generated using GOES water vapor satellite imagery. Brown indicates dry air. White, blue, and purple indicates moist air. An increase in moisture indicates slower air parcel lapse rates with elevation and hence an increase toward instability.

Sea-surface temperatures are overlaid with light blue isotherms. The 26 deg C isotherm is highlighted in red. Waters at and south of the 26 deg C isotherm indicate low-level warmth and hence faster environmental lapse rates with elevation (more instability). Waters north of the 26 deg C isotherm indicate slower environmental lapse rates with elevation (less instability).

...MID-LATITUDES DISCUSSION...
P1...On the heels of the complex frontal system in paragraph P2 is the next one entering the picture from the western US...anchored by a 1003 mb center in the western Dakotas in the above birdseye charts. Warm air advection ahead of this frontal system supports an upper anticyclone centered over NE New Mexico.

P2...Complex frontal system covering the northwest half of the discussion area (eastern North America and northwestern Atlantic...paragraph P1 of discussion #39) persists. A less-than-1000 mb frontal cyclone and associated supporting upper trough is splitting eastward and heading toward Europe. A 1002 mb frontal cyclone and associated supporting upper trough is centered over eastern Canada. The remnant low of Debby is no longer distinguishable witing this complex frontal system. Surface 1016 mb ridge in the SE Gulf of Mexico is building northward in last 24 hours while supported by upper convergence on the back side of the upper troughing....including a 1019 mb center W of Florida...1019 mb center over the SE US...1017 mb center over the eastern Great Lakes...and 1016 mb center over SW Hudson Bay. Finally...Texas cut-off upper low stemming from this weather system several days ago has weakened to an inverted upper trough...and this system has delivered yet another cut-off upper trough moving SE across the western Atlantic and Bahamas.

P3...Upper ridge over the western Atlantic and south Greenland remains split in three areas by mass cool air advection behind the complex frontal system in paragraph P2 above. The northern part is an upper anticyclone over south Greenland...the middle is an upper anticyclone in the open central Atlantic...and the southern has shifted southeast into the eastern Caribbean in advance of the cut-off upper trough mentioned at the very end of paragraph P2.

P4...Surface frontal cyclone that made landfall in Europe leaves behind a surface trough marked in the upper-right corner of the above charts. Cut-off upper vortex south of the Azores persists...splitting the open central Atlantic upper anticyclone (paragraph P3) into two anticyclones. Surface trough south of the Azores persists...today supported by split flow upper divergence between the NE edge of the upper vortex and NW edge of the eastern upper anticyclone. Finally...cut-off upper trough E of Bermuda persists...and its eastern divergence supports a surface trough marked on the 1200Z TAFB analysis. The SE Caribbean fragment of this cut-off upper trough has retrograded westward about the southermost upper anticyclone in paragraph P3...and into the central Caribbean.

P5...Open Atlantic surface ridge still has a strong center....which is now 1029 mb and SW of the Azores as of 1200Z TAFB. It will continue to weaken or hold steady strength as long as it remains vertically stacked with the less-convergent open central Atlantic upper anticyclone mentioned in paragraph P3.

...TROPICAL BELT DISCUSSION...
P6...Upper ridge in the western Gulf of Mexico persists...and has an upper anticyclonic center over the southeastern United States.

P7...Inverted upper trough over the Yucatan and southern Gulf of Mexico persists while retorgrading slowly west about the upper ridge in paragraph P6.

P8...Small upper ridge over the Panama area has shifted into Central America.

P9...Expansive east Atlantic upper ridge continues. In conjunction with the surface ridge in paragraph P5 and southernmost upper anticyclone in paragraph P2...deep-layered easterly flow exists across much of the Atlantic tropics that is advecting African desert dry air (brown shading in the above thermo birdseye chart) westward. Three inverted upper troughs on the south side of this east Atlantic upper ridge show up today...but not sure what caused them at this hour.

P10...Tropical wave crossing the Lesser Antilles in the previous discussion (formerly Invest 97-L) has continued across the eastern Caribbean Sea and is headed into the central Caribbean. It is about to become suppressed by central Caribbean upper vorticity mentioned at the very end of paragraph P4.

P11...A poorly-defined tropical wave midway between the Cape Verde Islands and the Lesser Antilles has been removed from today's 1200Z TAFB analysis as if it dissipated.

P12...Vigorous tropical wave over and south of the Cape Verde Islands in the previous discussion is now nearing the waters midway between the Cape Verdes and Lesser Antilles. This tropical wave is not nearly as impressive anymore while rolling into the dry air mentioned in paragraph P9.

P13...Although not yet in the scope of the above charts...the next strong tropical wave is about to enter the tropical waters of the Atlantic from western Africa. If the tropical wave in paragraph P12 is a good analogue...this tropical wave should not develop either.

Updated: 3:59 AM GMT on July 10, 2012

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2012 Atlantic Hurricane Season Birdseye Discussion #39

By: NCHurricane2009, 1:17 PM GMT on July 01, 2012

...JULY 1 2012...9:20 AM EDT...
As we push into July...Atlantic tropics have quieted with all areas of interest from the previous discussion diminishing.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...

This chart is generated based on surface analysis from the National Hurricane Center TAFB at 0000Z, and the 0123Z-released HPC analysis.

In light blue is upper air analysis, with 200 mb wind barbs calculated by GOES satellite imagery showing the upper-level wind direction. Based on the 200 mb wind barbs, blue-dashed lines are locations of upper troughs, blue-zig-zag lines are locations of upper ridges. Blue Ls are locations of upper lows, blue Hs are locations of upper ridges.

In red is surface analysis, with solid lines indicating locations of surface fronts, dashed lines indicating locations of surface troughs, and zig-zag lines indicating surface ridge axes. Ls indicate surface lows, Hs indicate surface highs.

...THERMODYNAMICS BIRDSEYE CHART...

This chart is generated using GOES water vapor satellite imagery. Brown indicates dry air. White, blue, and purple indicates moist air. An increase in moisture indicates slower air parcel lapse rates with elevation and hence an increase toward instability.

Sea-surface temperatures are overlaid with light blue isotherms. The 26 deg C isotherm is highlighted in red. Waters at and south of the 26 deg C isotherm indicate low-level warmth and hence faster environmental lapse rates with elevation (more instability). Waters north of the 26 deg C isotherm indicate slower environmental lapse rates with elevation (less instability).

...MID-LATITUDES DISCUSSION...
P1...Western North America surface frontal system (paragraph P1 of discussion #38) has since moved rapidly eastward across southern Canada...and merged with frontal system over the eastern US (paragraph P2 of discussion #38) at both the surface and upper-levels. At the surface...there are a variety of pressure centers below 1000 mb from eastern Canada to the waters SE of Greenland (marked in the above charts). An east-west front extends across the United States...and another front extends SW-NE across the western Atlantic Ocean where the remnant low of Debby (located NNE of Bermuda) is still embedded as of 0000Z TAFB. Surface 1018 mb ridge over the eastern US...once supported by upper convergence on the back side of this system's upper vorticity...has continued shifting southeast and is now a 1016 mb ridge centered in the SE Gulf of Mexico. Finally...west Gulf of Mexico cut-off upper low stemming from this weather system several days ago has moved into Texas.

P2...Upper ridge over the western Atlantic and south Greenland from the previous discussion has been split in three areas by mass cool air advection behind the complex frontal system in paragraph P1 above. The norhtern half is an upper anticyclone near south Greenland...the middle is an upper anticyclone in the open central Atlantic...and the southern is near Cuba and the Bahamas.

P3...Large upper trough in the north-central Atlantic (and its surface frontal cyclone) from the previous discussion has moved NE into Europe...and the surface frontal cyclone's tailing cold front is marked in the upper-right corner of the above charts. This upper trough has left behind a cut-off upper trough retrograding southwestward around the central Atlantic upper anticyclone mentioned in paragraph P2 above. The west end of this cut-off features an upper vortex south of the Azores...and it appears split flow upper divergence between the vortex and the flow going into the cut-off upper trough has causd a weak surface trough south of the Azores as of 0000Z TAFB. Finally...yet another cut-off upper trough was left E of Bermuda in the past days (in paragraph P4 of the last few discussions). This is now a cut-off upper vortex E of Bermuda whose tail end reaches into the SE Caribbean. The SE Caribbean fragment of this upper vorticity will soon retrograde westward about the southernmost upper anticyclone mentioned in paragraph P2.

P4...Open Atlantic surface ridge still has a strong center....which is now 1032 mb and west of the Azores as of 0000Z TAFB. The 1032 mb center was supported by upper convergence behind the upper trough mentioned in paragraph P3 above and upper convergence ahead of the central Atlantic upper anticyclone mentioned in paragraph P2 above. Now that the central Atlantic upper anticyclone is becoming vertically aligned with the 1032 mb center...the 1032 mb center may begin weakening.

...TROPICAL BELT DISCUSSION...
P5...Upper ridge over the southern Gulf of Mexico has undergone changes since the previous discussion. The remnant of Debby...part of the complex frontal system in paragraph P1...had cool air advection behind it such that upper troughing dug to the east of this upper ridge...which utlimately pushed the upper ridge into the western Gulf of Mexico. Meanwhile...upper divergence between the north boundary of this upper ridge and south boundary of the upper troughing triggered a surface trough trailing from the remnant of Debby. While the upper ridge retrograded into the west Gulf...it provided enhanced outflow over the surface trough that triggered a short-lived tropical disturbance that was mentioned in the tropical weather outlook of the National Hurricane Center. Now that this disturbance has made landfall in south Texas and NE Mexico...tropical development is no longer possible here.

P6...Cut-off upper vorticity in the eastern Caribbean was mentioned as a dissipating feature in the previous discussion (paragraph P8...discussion #38)...when in fact it continued to linger while retrograding westward around the upper ridge in paragraph P5 (that is...when that upper ridge was stronger and larger). This upper vorticity is now an inverted upper trough over the Yucatan and southern Gulf of Mexico.

P7...As a fragment of the upper vorticity in paragraph P6 retrograded westward out of the Caribbean...a small upper ridge in the southern Caribbean built it its wake. A tropical wave in the area (paragraph P10...discussion #38) interacted with the upper divergence of the small upper ridge to produce t-storms over the Panama area. The tropical wave has recently move into the eastern Pacific...while the small upper ridge continues to provide local outflow for storm activity in the Panama area.

P8...Expansive east Atlantic upper ridge continues. In conjunction with the surface ridge in paragraph P4 and southernmost upper anticyclone in paragraph P2...deep-layered easterly flow exists across much of the Atlantic tropics that is advecting African desert dry air (brown shading in the above thermo birdseye chart) westward. All embedded upper vorticity in this east Atlantic upper ridge has dissipated.

P9...Tropical wave southwest of the Cape Verde Islands in the previous discusison was a special feature on this blog and was briefly upgraded to Invest 97-L by the Naval Research Laboratory (NRL) of the US Navy. The tropical wave was successful in fighting off dry desert air thanks to enhanced poleward outflow provided by embedded upper vorticity in the paragraph P8 upper ridge. The upper vorticity dissipated...leaving the tropical wave to struggle against moderate easterly vertical shear on the south side of the paragraph P8 upper ridge...albiet split upper flow on the southwest quadrant of the same upper ridge helped the tropical wave gain more t-storm activity. As of this writing...the tropical wave is nearing the Lesser Antilles and is no longer a special feature while struggling in southerly vertical shear from the upper vorticity mentioned towards the end of paragraph P3.

P10...A poorly-defined tropical wave has been added by TAFB since the previous discussion....located midway between the Cape Verde Islands and the Lesser Antilles while struggling with dry air mentioned in paragraph P8. The western lobe of the paragraph P8 upper ridge has been inflated by latent heat release of the tropical wave in paragraph P9...and the eastern lobe of the paragraph P8 upper ridge has been inflated by latent heat release of the vigorous tropical wave in paragraph P11...with new upper vorticity forming in between the eastern and western lobes as a result. This tropical wave also remains suppressed by this upper vorticity.

P11...Yet another vigorous tropical wave has rolled off of western Africa...and is now located over and south of the Cape Verde Islands as of 0000Z TAFB. Its t-storm activity latent heat release has inflated the eastern lobe of the paragraph P8 upper ridge...this inflation allowing the tropical wave to begin carving out its own supportive upper outflow structure in this upper ridge. With supportive upper outflow allowing the tropical wave to fight off dry air mentioned in paragraph P8...coupled with low shear from deep-layered easterly flow also mentioned in paragraph P8...this tropical wave may become the next feature to watch for potential tropical development.

Updated: 2:45 PM GMT on July 01, 2012

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