NCHurricane2009's Blog

2012 Atlantic Hurricane Season Birdseye Discussion #167A (Special Update)

By: NCHurricane2009, 5:06 AM GMT on November 25, 2012

...SATURDAY NOVEMBER 24 2012...11:59 PM EDT...
The 2012 Atlantic Hurricane Season has likely ended. With one week to go in the season...computer models show a pattern of low-amplitude upper troughs and ridges traversing the Atlantic. Without a high-amplitude upper trough or major cut-off upper vortex expected...vertical wind shear will be high as to prevent subtropical cyclone development. Concerning the tropical belt of the Atlantic...surface tropical waves have stopped rolling off of Africa since late October. The remaining favorable upper ridge in the tropical Atlantic (paragraph P4 of full discussion #167) is shown in models to de-amplify over the course of the next week.

Full birdseye chart discussions will resume on this blog when the Atlantic hurricane season re-starts in June 2013. Special updates and or full birdseye discussions could resume before that time if any out of season tropical or subtropical activity occurs in the Atlantic basin.

Sometime early in 2013...I will be releasing post-storm reports for the 2012 Atlantic Hurricane Season which will include an evaluation of how my storm forecasts (issued on this blog) compared with that of the official forecasts from the National Hurricane Center.

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2012 Atlantic Hurricane Season Birdseye Discussion #167

By: NCHurricane2009, 6:38 PM GMT on November 23, 2012

...FRIDAY NOVEMBER 23 2012...1:39 PM EDT...
Shortly after the previous discussion was written...western Atlantic surface low had lost organized t-storm activity...but this early afternoon has regained t-storm activity while centered just north of Bermuda. Summary of how this feature has evolved in the last 24 hours is described in paragraph P2 below. Today is the final day for any potential subtropical cyclone development before the surface low hooks sharply northward toward cooler waters and into Atlantic Canada in the next 48 hours while the surface low gets steered by southeast half of the paragraph P1 upper trough/surface frontal system. However...such subtropical development appears unlikely as this system still lacks decent t-storm activity close to the center and continues to be analyzed with a non-tropical surface cold front in National Hurricane Center TAFB surface maps.

With one week left in the 2012 Atlantic Hurricane Season...will be looking at computer model runs tonight to assess what the large-scale weather pattern looks like for the remainder of hurricane season. If the forecast pattern does not appear conducive for anymore subtropical or tropical cyclone development...will write a special update declaring the end of my daily full birdseye discussions for the 2012 season.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...

This chart is generated based on surface analysis from the National Hurricane Center TAFB at 1200Z, and the 1330Z-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 US upper trough in the previous discussion has entered the central US. Eastern divergence of the upper trough supports surface frontal depression that has intensified from 999 to 992 mb over the last 24 hrs. This surface frontal depression has moved from north-central Minnesota to Lake Superior during this time. Western convergence of the upper trough supports strong 1039 mb surface ridge building into the western US. Strong northerly cold winds blowing over the warmer Great Lakes...generated between the 1039 mb ridge and 992 mb depression...will promote lake effect snow in the Great Lakes region during the next 24 hours.

P2...Broad 1004 to 1008 mb surface low offshore of the SE US in the previous discussion has intensified to 997 mb while moving ENE and passing just north of Bermuda. Intensification was supported by eastern divergence of associated cut-off upper trough. Upper vortex at north end of the cut-off upper trough has aligned with the surface 997 mb center...resulting in a deep-layered low. Upper convergence behind (west) of the deep-layered low supports 1024 mb surface ridging across the SE US...Gulf of Mexico...and Nw Caribbean.

P3...NE Atlantic upper trough in paragraph P3 of the previous discussion...east Canada upper trough in paragraph P2 of the previous discussion...and Azores upper trough in paragraph P3 of the previous discusion...have all merged into one large NE Atlantic upper trough. Less-than-1004 mb surface low crossing the Azores in paragraph P3 of the previous discussion is continuing ENE toward Europe while supported by the eastern divergence of this large NE Atlantic upper trough. Marine 994 mb surface frontal depression just SW of Greenland in paragraph P2 of the previous discussion is moving east by the south tip of Greenland...and should soon weaken beneath the western convergence of the NE Atlantic upper trough. Greater-than-1020 mb surface ridge offshore of Atlantic Canada is supported by this upper convergence. 1025 mb surface ridge just north of the Canary Islands in paragraph P3 of the previous discussion is breaking up into a 1018 to 1024 mb ridge covering the east half of the above atmo chart while this ridge erodes in advance of less-than-1004 mb surface low heading toward Europe.

...TROPICAL BELT DISCUSSION...
P4...Upper ridge over the central tropical Atlantic persists. Upper divergence west of this upper ridge supports scattered t-storm activity across the central Caribbean Sea.

P5...Cut-off upper trough W of the Cape Verde Islands persists...but continues to be squished out by growth of paragraph P4 upper ridge (this upper ridge is growing thanks to low-level warm air advection ahead of paragraph P2 997 mb deep-layered low). What is left of surface troughing formerly supported by eastern divergence of this cut-off upper trough is SE of the Lesser Antilles. This surface troughing continues to be steered west by the 1018 to 1024 mb ridge mentioned in paragraph P3 above.

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2012 Atlantic Hurricane Season Birdseye Discussion #166

By: NCHurricane2009, 8:21 PM GMT on November 22, 2012

...THURSDAY NOVEMBER 22 2012...3:20 PM EDT...
This discussion has been released 60 hours since the previous...due to interruptions from me traveling on Thanksgiving holiday.

Still monitoring weather in the western Atlantic Ocean for potential subtropical cyclone development. As expected...first phase of the western Atlantic surface low has not developed into a subtropical cyclone due to increased westerly vertical shear below de-amplified paragraph P3 southern upper trough. This first phase has since exited stage right and is moving across the Azores this afternoon.

Second phase has begun in association with broad 1004 to 1008 mb surface low offshore of the southeastern United States as mentioned in paragraph P2 below. As remarked in that paragraph...this surface low is supported by eastern divergence of a cut-off upper trough...a feature which currently has an upper vortex at its north end that is reducing the vertical shear and whose de-stabilizing cold upper air is supporting increasingly organizing t-storms across the northwest half of the 1004 to 1008 mb surface center. In addition...the formation of this surface center just north of the 26 deg C sea-surface temperature isotherm supports low-level warmth for additional instability. Given all this information...chances for subtropical cyclone development are increasing. This feature may warrant a special update on my blog later today...or may be upgraded to a special feature in my next full blog update. This feature and cut-off upper trough will be headed eastward toward Bermuda in the next 24 hours...then hook northward toward Atlantic Canada by 72 hours while steered by the southeast half of the paragraph P1 upper trough/surface frontal system.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...

This chart is generated based on surface analysis from the National Hurricane Center TAFB at 1200Z, and the 1330Z-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 upper trough and surface frontal system...new to this discussion...has entered the top-left of the above charts. The upper trough is currently over the western US. Eastern divergence of the upper trough supports 999 mb surface frontal depression over north-central Minnesota. Western convergence of the upper trough supports 1023 mb SW US surface ridge.

P2...Upper trough and surface frontal system crossing the central US in paragraph P1 of the previous discussion is now over eastern Canada. Eastern divergence of the upper trough supports marine 994 mb surface frontal depression just SW of Greenland. South fragment of this upper trough has cut-off offshore of the SE US...where eastern upper divergence of this cut-off supports a 1004 to 1008 mb surface low that is an extension of the west lobe of the Azores surface low mentioned at the end of paragraph P3 below. Western convergence of the upper trough and its cut-off south fragment supports lengthy 1020 to 1028 mb surface ridging extending from east Mexico...across the eastern US...and into Atlantic Canada.

P3...Northern upper trough crossing the Atlantic high seas in the previous discussion has entered the NE Atlantic (a south fragment of this upper trough has just exited the picture into NW Africa where its eastern divergence supports NW Africa surface trough seen in top-right of above atmo chart). Southern upper trough in the last 60 hours has moved from the W Atlantic/W Caribbean and into the open Atlantic waters near the Azores. Lengthy surface frontal/troughal activity across the Atlantic persists while supported by eastern divergence of the northern and southern upper troughs. This frontal/troughal activity continues to curl into surface cyclone that has moved into the waters east of Greenland in the last 60 hours...and this cyclone remains associated with the northern upper trough. Western convergence of the northern upper trough supports strong surface ridge that has long since moved offshore of the NE US in the past 60 hrs. This surface ridge was 1027 mb just south of the Azores as of 0000Z Nov 21...and is 1025 mb just north of the Canary Islands as of 1200Z today. The 1013 mb low offshore of the SE US in the previous discussion continues to be supported by eastern divergence of the southern upper trough...and because this upper trough has moved toward the Azores as mentioned above...it is now the less-than-1004 mb low approaching the Azores at this hour.

...TROPICAL BELT DISCUSSION...
P4...Upper ridge over the central tropical Atlantic persists. Upper divergence west of this upper ridge supports scattered t-storm activity across the central Caribbean Sea. Meanwhile...upper convergence east of this upper ridge axis formerly supported a north Atlantic surface ridge 60 hours ago that has been long-absorbed by the 1025 mb Canary Islands ridge mentioned in paragraph P3.

P5...Cut-off upper vortex midway between the Cape Verde Islands and Lesser Antilles has weakened into an upper trough that has been pushed east toward the Cape Verde Islands by growth of the paragraph P4 upper ridge. Upper divergence east of this cut-off upper trough supports some cloudiness. What is left of surface troughing formerly supported by this upper divergence has moved west while steered by 1025 mb Canary Islands ridge mentioned in paragraph P3. North fragment of this surface troughing is currently NE of the Lesser Antilles becoming assimilated into lengthy surface frontal/troughal activity mentioned in paragraph P3. South fragment of this surface troughing is well SE of the Lesser Antilles.

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2012 Atlantic Hurricane Season Birdseye Discussion #165

By: NCHurricane2009, 9:40 AM GMT on November 20, 2012

...TUESDAY NOVEMBER 20 2012...4:40 AM EDT...
Weather in the western Atlantic Ocean deteriorating due to anticipated formation of surface low as mentioned towards the end of paragraph P2. In the previous intro sections of these discussions....this event has been presented as one that will have two surface lows. However with model solutions moreso showing this as a single broad surface low event...will go ahead and now present this as a single surface low event.

This surface low has formed with the support of eastern divergence of the southern upper trough in paragraph P2. In addition...the northern upper trough in paragraph P2 has created a tight pressure gradient with respect to the paragraph P3 upper ridge...resulting in a strong upper westerly jet just east of the surface low. Upper winds accelerating into the jet are enhancing the upper divergence over the surface low such that it remains vigorous. Despite being positioned just north of the 26 deg C sea-surface temperature isotherm and being below a cold core upper vortex at the north end of the paragraph P2 southern upper trough...the current upper vortex does not appear cold (de-stabilizing) enough for subtropical cyclone formation as their is a lack of thunderstorms at the center of the surface low. In addition...the paragraph P2 southern upper trough will soon de-amplify overhead of the surface low...which will increase the shear across this system in the short-term.

Beginning in 24 to 36 hours...this surface low will receive boost from eastern divergence of the next upper trough. This next upper trough is currently associated with the western US frontal system mentioned in paragraph P1. This next upper trough is expected to amplify into an upper vortex over the surface low...which will once again reduce the shear over the system. If cold enough for instability...this upper vortex will be the final shot this system has of becoming a subtropical cyclone.

...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...Western US surface frontal system and attendant upper trough have entered the top-left of the above charts. These features will be crossing the central US later today. Western convergence of the attendant upper trough supports the 1028 and 1022 mb western US surface ridge centers shown in the top-left.

P2...Northern upper trough continues crossing the Atlantic high seas. Southern upper trough persists offshore of the SE US and W Caribbean...with an upper vortex at the north end of this upper trough. Lengthy W Atlantic surface cold front persists while supported by eastern divergence of both upper troughs. This cold front continues to curl into surface frontal cyclone near the south tip of Greenland...and this cyclone remains associated with the northern upper trough. Western convergence of the northern upper trough supports strong 1032 mb ridge moving offshore into the NW Atlantic from the NE US. Western convergence of the southern upper trough supports surface ridging over the western Gulf of Mexico and Central America. The 1013 mb low offshore of the Carolinas in the previous discussion...located along the SW end of the aforementioned W Atlantic front...has been absorbed by larger/broader 1012 mb surface low that has formed more offshore. This larger/broader surface low is supported by eastern divergence of the southern upper trough.

...TROPICAL BELT DISCUSSION...
P3...Upper ridge axis over the central tropical Atlantic persists. Upper divergence west of this upper ridge supports scattered t-storm activity across the central Caribbean Sea. A 1008 mb low located along the surface ITCZ and near eastern Panama continues to be marked in consecutive 6-hourly TAFB surface maps...a feature perhaps also supported by this upper divergence. Meanwhile...upper convergence east of this upper ridge axis formerly supported the north Atlantic surface ridge (currently 1020 mb). This surface ridge is now eroding in advance of the large surface cyclone near the south tip of Greenland (paragraph P2)...and this surface ridge will soon be replaced by 1032 mb ridge mentioned in paragraph P2.

P4...Cut-off upper vortex midway between the Cape Verde Islands and Lesser Antilles persists. Upper divergence east of this upper vortex supports some scattered t-storm activity. Surface troughing formerly supported by this upper divergence currently remains beneath the upper vortex.

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2012 Atlantic Hurricane Season Birdseye Discussion #164

By: NCHurricane2009, 5:13 AM GMT on November 19, 2012

...MONDAY NOVEMBER 19 2012...12:30 AM EDT...
Weather in the western Atlantic Ocean to deteriorate in the next days due to two strong surface lows forecast to develop. However...the models remain west with the formation of the first of the two lows such that solutions increasingly consider both features as one.

Computer models agree that by 30 hrs...a surface low will form west of Bermuda and along the western Atlantic front mentioned in paragraph P2. This surface low is expected to form with the support of eastern divergence of the southern upper trough in paragraph P2. In fact...the 1013 mb surface low offshore of the Carolinas...mentioned towards the end of paragraph P2...may be the beginnings of this surface low. In addition...the northern upper trough in paragraph P2 is beginning to create a tight pressure gradient with respect to the paragraph P4 upper ridge...resulting in a strong upper westerly jet just east of the developing surface low. Upper winds accelerating into the jet are expected to enhance the upper divergence over the surface low such that it develops quickly. Despite a forecast formation just north of the 26 deg C sea-surface temperature isotherm...this first surface low should not develop into a subtropical cyclone due to hostile shear from the upper jet.

Computer models develop a more impressive second surface low just offshore of the southeastern United States beginning in 60 hours. This second surface low is expected to develop in upper divergence east the upper trough currently associated with the western US frontal system mentioned in paragraph P1. This second surface low will either absorb the above-mentioned first surface low...the first one will jump left while evolving into this second surface low...or the first one will simply exit stage right. Because the upper trough is expected to amplify into an upper vortex during this phase...this could reduce the shear. Coupled with formation just north of the 26 deg C waters and potentially de-stabilizing cold upper air with the upper vortex...their is some potential for subtropical cyclone development with this second surface low.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...

This chart is generated based on surface analysis from the National Hurricane Center TAFB at 1800Z, and the 1926Z-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...Shortwave upper trough previously over the north-central US is now over eastern Canada and will soon merge with the northern upper trough mentioned in paragraph P2. The surface depressions associated with the shortwave upper trough have been absorbed by a surface frontal system entering the top-left of the above charts from the western US. Low-level warm air advection ahead of the western US frontal system supports the central US upper ridge.

P2...Northern upper trough continues crossing the Atlantic high seas. Southern upper trough persists over the SE US...E Gulf of Mexico...and W Caribbean...with an upper vortex at the north end of this upper trough. Lengthy W Atlantic surface cold front persists while supported by eastern divergence of both upper troughs. Surface frontal cyclone moving across the southern tip of Greenland remains associated with the northern upper trough. Western convergence of the northern upper trough supports strong 1040 mb ridge over the NE US. Western convergence of the southern upper trough supports surface ridging over the western Gulf of Mexico and Central America. Surface low moving ENE across the Atlantic high seas...located along the aforementioned W Atlantic front...has become absorbed by aforementioned surface cyclone near the south tip of Greenland. The 1019 mb low ENE of Bermuda in the previous discussion...yet another feature along the surface front...has dissipated. The SW end of the front just offshore of the Carolinas has developed a surface low (currently 1013 mb) as anticipated in the previous discussion. This surface low is supported by eastern divergence of the southern upper trough.

P3...NE Atlantic upper trough and associated surface cold front is exiting the top-right of the above charts from western Europe.

...TROPICAL BELT DISCUSSION...
P4...Upper ridge axis over the central tropical Atlantic persists. Upper divergence west of this upper ridge continues to support t-storm activity across the central Caribbean Sea. A 1010 mb low located along the surface ITCZ and near eastern Panama continues to be marked in consecutive 6-hourly TAFB surface maps...a feature perhaps also supported by this upper divergence. Meanwhile...upper convergence east of this upper ridge axis formerly supported the north Atlantic surface ridge (currently 1022 mb). This surface ridge is now supported by upper convergence on the back sides of the northern upper trough in paragraph P2 and upper trough in paragraph P3.

P5...Cut-off upper trough NW of the Cape Verde Islands has amplified into an upper vortex midway between the Cape Verde Islands and Lesser Antilles. Upper divergence east of this upper vortex supports a comma-shaped area of t-storm clouds. Surface troughing formerly supported by this upper divergence has shifted west beneath the upper vortex while steered by 1022 mb north Atlantic surface ridge mentioned in paragraph P4.

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2012 Atlantic Hurricane Season Birdseye Discussion #163

By: NCHurricane2009, 4:19 AM GMT on November 18, 2012

...SATURDAY NOVEMBER 17 2012...11:30 PM EDT...
Weather in the western Atlantic Ocean to deteriorate in the next days due to two strong surface lows forecast to develop. However...the models have shifted west with the formation of the first of the two lows such that solutions increasingly consider both features as one.

Computer models agree that by 54 hrs...a surface low will form west of Bermuda and along the western Atlantic front mentioned in paragraph P2. 24 hrs ago...solutions showed the formation of the low east of Bermuda...so this is a westward shift from the previous. This surface low is expected to form with the support of eastern divergence of the southern upper trough in paragraph P2...and with this upper trough currently more amplified than shown in the 18Z GFS model...the formation of this surface low could occur even further west toward the SE US coast. In fact...this surface low may already be in the formative stages as evidenced by the statements currently towards the end of paragraph P2. In addition...the northern upper trough in paragraph P2 is beginning to create a tight pressure gradient with respect to the paragraph P4 upper ridge...resulting in a strong upper westerly jet just east of the developing surface low. Upper winds accelerating into the jet are expected to enhance the upper divergence over the surface low such that it develops quickly. Despite a forecast formation just north of the 26 deg C sea-surface temperature isotherm...this first surface low should not develop into a subtropical cyclone due to hostile shear from the upper jet.

Computer models develop a more impressive second surface low just offshore of the southeastern United States beginning in 84 hours. This second surface low is expected to develop in upper divergence east of an impressive upper trough that has not yet entered the scope of this discussion. Because the above-mentioned first surface low is now expected to form further west than thought before...this second surface low will either absorb the first one...or the first one will jump west while evolving into this second surface low. Because the upper trough is expected to amplify into an upper vortex during this phase...this could reduce the shear. Coupled with formation just north of the 26 deg C waters and potentially de-stabilizing cold upper air with the upper vortex...their is some potential for subtropical cyclone development with this second surface low.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...

This chart is generated based on surface analysis from the National Hurricane Center TAFB at 1800Z, and the 1926Z-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...Shortwave upper trough has entered the top-left corner of the above charts and is currently located over the north-central US. Eastern divergence of the shortwave upper trough supports a 1020 mb depression over SE Manitoba and 1014 mb depression over the Dakotas. Western convergence of the upper trough supports 1026 mb ridge over the SW US. Central US upper ridge axis ahead of this system has split into one upper ridge axis over Mexico and the south-central US...and a second upper ridge axis over the Great Lakes.

P2...Large North America upper trough has split into two. The northern upper trough is entering the Atlantic high seas between Canada and Greenland. The southern upper trough is located over the SE US...E Gulf of Mexico...and W Caribbean. Lengthy W Atlantic surface cold front persists while supported by eastern divergence of both upper troughs. Surface frontal cyclone over eastern Canada in the previous discussion....now associated with the northern upper trough...is moving across the south tip of Greenland. Western convergence of the northern upper trough supports strong 1040 mb ridge over the NE US. Western convergence of the southern upper trough supports 1028 mb ridge over eastern Mexico. 1001 mb low centered just SE of Newfoundland in the previous discussion has raced ENE into the north Atlantic while becoming associated with the eastern divergence of the northern upper trough. This surface low continues to be located along the aforementioned W Atlantic surface front. The 1016 mb low just NW of Bermuda in the previous discussion...yet another feature along the surface front...has weakened to 1019 mb at a location ENE of Bermuda. The SW end of the front just offshore of the Carolinas has become kinked with increased cloudiness spreading onshore...a sign that yet another surface low maybe forming along the front. Such a surface low would be supported by eastern divergence of the southern upper trough.

P3...NE Atlantic upper trough is moving into western Europe from the Iberian peninsula. Surface frontal depression associated with the upper trough is currently 1002 mb while supported by the eastern divergence of the upper trough. This depression has made landfall across Portugal and Spain.

...TROPICAL BELT DISCUSSION...
P4...Upper ridge axis over the central tropical Atlantic continues to be expanded northward into the Atlantic high seas via warm air advection ahead of the W Atlantic surface front mentioned in paragraph P2. Upper divergence west of this upper ridge continues to support t-storm activity across the central Caribbean Sea. A 1010 mb low located along the surface ITCZ and near eastern Panama has been marked in the last three 6-hourly TAFB surface maps...a feature perhaps also supported by this upper divergence. Meanwhile...upper convergence east of this upper ridge axis supports the north Atlantic surface ridge (currently 1028 mb).

P5...Cut-off upper trough NW of the Cape Verde Islands persists. Expansive upper divergence east of this cut-off upper trough supports a wide area of clouds that continues overspreading the Cape Verde Islands and eastern tropical Atlantic. This upper divergence continues to support relatively fresh surface troughing midway between the Cape Verde Islands and the Lesser Antilles.

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2012 Atlantic Hurricane Season Birdseye Discussion #162

By: NCHurricane2009, 1:13 AM GMT on November 17, 2012

...FRIDAY NOVEMBER 16 2012...8:14 PM EDT...
Weather in the western Atlantic Ocean to deteriorate in the next days due to two strong surface lows forecast to develop.

Computer models agree that by 80 hrs...a surface low will form east of Bermuda and along the western Atlantic front mentioned in paragraph P2. Tonight's 18Z GFS model shows the surface low forming in eastern upper divergence of a southern fragment of the paragraph P2 upper trough. At the same time...the northern fragment of the upper trough is expected to create a tight pressure gradient with respect to the paragraph P4 upper ridge...resulting in a strong upper westerly jet just east of the surface low. Upper winds accelerating into the jet are expected to enhance the upper divergence over the surface low such that it develops quickly. Despite a forecast formation just north of the 26 deg C sea-surface temperature isotherm...this first surface low should not develop into a subtropical cyclone due to hostile shear from the upper jet.

While the first surface low then moves out to sea...computer models develop a more impressive second surface low just offshore of the southeastern United States beginning in 111 hours. This second surface low is expected to develop in upper divergence east of an impressive upper trough that has not yet entered the scope of this discussion. Because the upper trough is expected to amplify into an upper vortex over the surface low...this could reduce the shear. Coupled with formation just north of the 26 deg C waters and potentially de-stabilizing cold upper air with the upper vortex...their is some potential for subtropical cyclone development with this second surface low.

...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...Shortwave upper trough is entering the top-left corner of the above charts from western Canada...but is not quiet yet in the scope of the charts. Eastern divergence of the shortwave upper trough supports a 1015 mb depression over SE Montana and 1019 mb depression over Manitoba. Low-level warm air advection ahead of the depressions supports an upper ridge axis entering the central US.

P2...Large surface low east of Greenland...currently just outside of the top-center of the above charts...persists thanks to divergence east of the major North America upper trough. This large surface low is pushing a surface front into the NE Atlantic and western Europe seen in the top-right of the above charts. Lengthy W Atlantic surface cold front formerly extending from the large surface low persists. The Gulf of Mexico fragment of the front has decayed into surface troughs. Surface frontal cyclone over Hudson Bay in the previous discussion....also supported by the eastern divergence of the major upper trough...is moving into eastern Canada. Western convergence of the major upper trough continues to support strong surface ridging across the US. Eastern divergence of the major upper trough continues to support a W Atlantic surface low that has intensified to 1001 mb currently centered just SE of Newfoundland. This surface low continues to be located along the aforementioned W Atlantic surface front. The 1018 mb low just offshore of the Carolinas in the previous discussion...yet another feature along the surface front and supported by the eastern divergence of the major upper trough...has intensified to 1016 mb at a location just NW of Bermuda.

P3...NE Atlantic cut-off upper vortex midway between the Azores and Canary Islands has weakened into an upper trough heading toward western Europe. Surface frontal depression associated with the upper trough has intensified to 999 mb while tapping into the eastern divergence of the upper trough. This 999 mb depression will soon make landfall across Portugal and Spain.

...TROPICAL BELT DISCUSSION...
P4...Upper ridge axis over the central tropical Atlantic continues to be expanded northward into the Atlantic high seas via warm air advection ahead of the W Atlantic surface front mentioned in paragraph P2. Upper divergence west of this upper ridge has supported an increase in t-storm activity across the central Caribbean and eastern Bahamas in the last 24 hrs. Upper convergence east of this upper ridge axis supports the north Atlantic surface ridge (currently 1027 mb).

P5...Cut-off upper trough NW of the Cape Verde Islands persists. Expansive upper divergence east of this cut-off upper trough supports a wide area of t-storm clouds that continues overspreading the Cape Verde Islands and eastern tropical Atlantic. This upper divergence has also triggered new surface troughing midway between the Cape Verde Islands and the Lesser Antilles...while the previous surface troughing in this area has dissipated in the western convergence on the back side of the cut-off upper trough.

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2012 Atlantic Hurricane Season Birdseye Discussion #161

By: NCHurricane2009, 1:08 AM GMT on November 16, 2012

...THURSDAY NOVEMBER 15 2012...8:09 PM EDT...
Tropical activity in the Atlantic remains calm as we enter the final two weeks of hurricane season.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...

This chart is generated based on surface analysis from the National Hurricane Center TAFB at 1800Z, and the 1931Z-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...Large surface low east of Greenland...currently just outside of the top-center of the above charts...has intensified thanks to divergence east of the major North America upper trough that continues to persist. A very lengthy surface cold front still extends from the exiting surface low...now stretched across the western Atlantic and Gulf of Mexico. SW fragment of the front has split off as a surface trough near the east coast of Mexico. East-west front across southern Canada in the previous discussion has developed a surface frontal cyclone currently over Hudson Bay also supported by the eastern divergence of the major upper trough. Western convergence of the major upper trough continues to support strong surface ridging across the US. Eastern divergence of the major upper trough continues to support a W Atlantic surface low that has intensified to 1008 mb currently centered just south of Newfoundland. This surface low has merged with aforementioned W Atlantic surface front. The W Atlantic surface front has also developed a new 1018 mb low just offshore of the Carolinas also supported by the eastern divergence of the major upper trough.

P2...NE Atlantic cut-off upper vortex persists midway between the Azores and Canary Islands. Surface frontal depression associated with the upper vortex has continued to whirl cyclonically beneath the upper vortex...and has strengthened from 1002 to 1000 mb since the previous discussion while now tapping into the eastern divergence of the upper vortex.

...TROPICAL BELT DISCUSSION...
P3...Upper ridge axis over the central tropical Atlantic continues to be expanded northward into the Atlantic high seas via warm air advection ahead of the W Atlantic-to-Gulf of Mexico surface front mentioned in paragraph P1. New east Caribbean surface trough supported by upper divergence west of this upper ridge has dissipated. Upper convergence east of this upper ridge axis supports the north Atlantic surface ridge (currently 1029 mb).

P4...Cut-off upper trough NW of the Cape Verde Islands persists. Expansive upper divergence east of this cut-off upper trough supports a wide area of t-storm clouds that has overspread the Cape Verde Islands and eastern tropical Atlantic. Surface troughing formerly supported by this upper divergence is still located midway between the Cape Verde Islands and Lesser Antilles...and remains inactive while now suppressed by the western convergence on the back side of the cut-off upper trough.

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2012 Atlantic Hurricane Season Birdseye Discussion #160

By: NCHurricane2009, 11:55 AM GMT on November 15, 2012

...THURSDAY NOVEMBER 15 2012...6:55 AM EDT...
Tropical activity in the Atlantic remains calm as we enter the final two weeks of hurricane season. The GOES satellite derived 200 mb wind barbs in the atmospheric features chart are currently not functioning. The upper-level features in the chart are therefore marked based on the upper-level wind barbs from http://www.goes.noaa.gov/WINDS/fullIREast.htm.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...

This chart is generated based on surface analysis from the National Hurricane Center TAFB at 0600Z, and the 0729Z-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 gale over Greenland and surface frontal low over Canada's Hudson Bay...both mentioned in paragraph P1 of the previous discussion...have merged into one large surface low east of Greenland that has exited the picture from the top-center. A very lengthy surface cold front still extends from the exiting surface low...now stretched across the western Atlantic and Gulf of Mexico. Just before merging with the exiting surface low...the surface frontal low over Canada's Hudson Bay has left behind an east-west front across southern Canada seen in the top-left of the above charts. Major upper trough covering North America persists. Western convergence of the major upper trough continues to support strong surface ridging across the US. Eastern divergence of the major upper trough continues to support a W Atlantic surface low that has moved NNE across Bermuda...and is currently 1015 mb while positioned just NE of Bermuda.

P2...NE Atlantic upper trough has exited the above charts from the top-right except for a cut-off upper vortex that has developed midway between the Azores and Canary Islands in association with locally maximal cool air advection of 997 mb surface frontal depression that formed NE of the Azores during the previous discussion. This depression has weakened to 1002 mb while whirling cyclonically beneath the non-divergent environment directly under the upper vortex.

...TROPICAL BELT DISCUSSION...
P3...Upper ridge axis over the central tropical Atlantic has been expanded northward toward Greenland via warm air advection ahead of the W Atlantic-to-Gulf of Mexico surface front and 1015 mb W Atlantic surface low both mentioned in paragraph P1. Upper divergence west of this upper ridge and east of the paragraph P1 major upper trough has supported the formation of a new eastern Caribbean surface trough. Upper convergence east of this upper ridge axis supports the north Atlantic surface ridge (currently greater-than-1032 mb) mentioned previously in paragraph P1 of discussion #159.

P4...Cut-off upper trough NW of the Cape Verde Islands persists. Expansive upper divergence east of this cut-off upper trough supports a wide area of t-storm clouds. Surface troughing formerly supported by this upper divergence continues to be steered westward by the paragraph P3 north Atlantic surface ridge. As a result...the surface troughing is now located midway between the Cape Verde Islands and Lesser Antilles...and has entered the unfavorable western convergence on the back side of the cut-off upper trough that is keeping the surface troughing inactive.

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2012 Atlantic Hurricane Season Birdseye Discussion #159

By: NCHurricane2009, 9:34 AM GMT on November 14, 2012

...WEDNESDAY NOVEMBER 14 2012..4:34 AM EDT...
As forecast...a surface low has developed in the western Atlantic. However as expected...the dynamics are not favorable for subtropical cyclone development as highlighted towards the end of paragraph P1.

New surface trough in association with former eastern Atlantic upper vortex has track westward into hostile upper winds. Therefore no development is expected here either. See paragraph P5 for update statement on this system.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...

This chart is generated based on surface analysis from the National Hurricane Center TAFB at 0000Z, and the 0126Z-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...The surface frontal gale centered over Canada's southern Hudson Bay in the previous discussion has moved rapidly NE into Greenland and exited the scope of the above charts from the top-center. Low-level warm air advection ahead of the exiting gale supports NW Atlantic upper ridge whose eastern convergence supports a surface ridge that is now 1039 mb in the north Atlantic. A very lengthy surface cold front extends from the exiting gale...stretched across the east coast of North America and Gulf of Mexico. Large western US upper trough in the previous discussion supporting the exiting gale is now a major upper trough covering North America and the western Caribbean Sea. This major upper trough is being re-enforced by cool air advection behind cold front/surface low pushing SE into the picture from Canada's Hudson Bay. Western convergence of the major upper trough meanwhile supports a strong surface ridge across the US. The major upper trough has also absorbed the W Atlantic southern cut-off upper trough mentioned in paragraph P2 of previous discussion #158. Prior to absorption...the eastern divergence of the cut-off upper trough supported the formation of a 1013 mb W Atlantic surface low located just SSW of Bermuda. This W Atlantic surface low is currently exposed to high SW vertical shear ahead of the above-mentioned major upper trough...and expect it to track northward quickly into cooler waters below 26 deg C. Therefore expect no subtropical cyclone development from this surface low.

P2...Northern upper trough moving across the Atlantic high seas in the previous discussion is now in the NE Atlantic. The associated intense 968 mb gale in the previous discussion has weakened considerably and exited the picture while the gale continued to be trapped beneath the non-divergent axis of the upper trough. Cold front attached to the gale remains in the picture...currently extending to waters in the vicinity of the Azores. A new 997 mb frontal depression is located along this cold front and just NE of the Azores while supported by the eastern divergence of the upper trough.

P3...What is left of the deep-layered ridge centered near the Azores has been assimilated into the 1039 mb north Atlantic surface ridge mentioned in paragraph P1.

...TROPICAL BELT DISCUSSION...
P4...Upper ridge axis over the central tropical Atlantic persists. Upper divergence west of this upper ridge and east of the cut-off southern upper trough in paragraph P1 formerly supported an eastern Caribbean surface trough that is now absorbed into the 1013 mb west Atlantic surface low mentioned in paragraph P1.

P5...Cut-off upper vortex NW of the Cape Verde Islands has opened into an upper trough due to the passage of the paragraph P2 NE Atlantic upper trough just to the north. Expansive upper divergence east of this cut-off upper trough supports a wide area of scattered t-storm clouds. Relatively new surface trough that developed in the same upper divergence has tracked westward while steered by the 1039 mb north Atlantic surface ridge in paragraph P1. On this track...this new surface trough has entered the unfavorable western convergence on the back side of the cut-off upper trough. The previous and older surface trough midway between the Cape Verde Islands and Lesser Antilles has finally dissipated in this same upper convergence in the last 24 hrs.

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2012 Atlantic Hurricane Season Birdseye Discussion #158

By: NCHurricane2009, 12:51 AM GMT on November 13, 2012

...MONDAY NOVEMBER 12 2012..7:51 PM EDT...
Computer models continue to agree that a surface low will develop in the western Atlantic in the timeframe that is now 24 hours. However the dynamics are not favorable for subtropical cyclone development as highlighted in paragraph P2.

A new surface trough has developed in association with an eastern Atlantic upper vortex that was previously a special feature in discussion #155. Like the previous surface trough with this system...the new surface trough could track westward into hostile upper winds while steered by the paragraph P3 deep-layered ridge. Therefore not re-upgrading the upper vortex to a special feature at this time. See paragraph P6 for update statement on this system.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...

This chart is generated based on surface analysis from the National Hurricane Center TAFB at 1800Z, and the 1932Z-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...The surface frontal gale centered over NW Minnesota in the previous discussion has moved rapidly NE and is currently located across Canada's southern Hudson Bay. This gale has strengthened to 988 mb from eastern divergence of large western US upper trough. Western convergence of the upper trough meanwhile supports a 1039 mb western US surface ridge. Low-level warm air advection ahead of the 988 mb gale supports an upper ridge that has moved from the central US to SE Canada/the NW Atlantic in the last 36 hrs. Eastern convergence of the upper ridge supports a surface ridge that is now 1038 mb while it has moved offshore from the eastern US/Canada into the western Atlantic.

P2...Large upper trough spanning east Canada...the western Atlantic...and Caribbean has split into two upper troughs. The northern upper trough is currently moving east across the Atlantic high seas and southern Greenland while the southern upper trough has become cut-off in the western Atlantic and Caribbean at a location south of the NW Atlantic upper ridge mentioned in paragraph P1. The intense 958 mb surface frontal gale passing by the southern tip of Greenland in the previous discussion is currently SE of Greenland while weakening to 968 mb while whirling into a position beneath the non-divergent northern upper trough axis. Expect rough seas to continue in the Atlantic high seas...and expect high winds to continue across southern Greenland and over open waters in the vicinity of this gale until the gale weakens further. Computer models agree that by 24 hours...eastern divergence of the aforementioned southern cut-off upper trough will support a W Atlantic surface low. This W Atlantic surface low will be exposed to high SW vertical shear as the cut-off never closes off into an upper vortex...and the surface low will track northward quickly into cooler waters below 26 deg C. Therefore...this forecast surface low is not expected to develop into a subtropical cyclone.

P3...Deep-layered north Atlantic ridge...currently with a 1027 mb surface center...persists now at a location just east of the Azores.

P4...Upper trough/surface cold front moving into western Europe in the previous discussion has exited the scope of the above charts from the upper-right corner.

...TROPICAL BELT DISCUSSION...
P5...Upper ridge axis over the central tropical Atlantic persists. Upper divergence west of this upper ridge and east of the cut-off southern paragraph P2 upper trough supports a surface trough that has moved westward from the Lesser Antilles into the eastern Caribbean. The surface trough has been steered westward by the 1038 mb western Atlantic surface ridge mentioned in paragraph P1.

P6...Cut-off upper vortex NW of the Cape Verde Islands persists. Expansive upper divergence east of the upper vortex continues to support a large comma shaped t-storm area that continues overspreading the Cape Verde Islands and eastern tropical Atlantic. A new surface trough has developed in the last 24 hrs while supported by the same upper divergence. Elsewhere...the previous and old surface trough that was spawned in the upper divergence...located midway between the Cape Verde Islands and Lesser Antilles as of the previous discussion...has continued to track westward while steered by the 1027 mb ridge in paragraph P3. On this continued track...this old surface trough has continued across the south side of the upper vortex where westerly vertical shear is inhibiting it. It is also suppressed by dry sinking air supported by the western convergence of the upper vortex.

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2012 Atlantic Hurricane Season Birdseye Discussion #157

By: NCHurricane2009, 3:50 PM GMT on November 11, 2012

...SUNDAY NOVEMBER 11 2012..10:50 AM EDT...
Computer models continue to agree that a surface low will develop in the western Atlantic in the timeframe that is now 60 hours. However the dynamics are not favorable for subtropical cyclone development as highlighted in paragraph P2.

...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...Gale pushing across Canada's Hudson Bay in the previous discussion has become absorbed by the 958 mb gale in paragraph P2. The gale centered over southern Wyoming in the previous discussion is maintaining strength at 997 mb while moving into NW Minnesota. This gale is maintaining strength from eastern divergence of an upper trough entering the top-left of the above charts from the western US. Low-level warm air advection ahead of the 997 mb gale supports a central US upper ridge. Eastern convergence of the upper ridge supports a 1030 mb eastern US surface ridge and 1030 mb eastern Canada surface ridge. Low-level southerlies between the 998 mb gale and 1030 mb ridge centers are in directional shear with respect to upper westerlies across the central US upper ridge. The shear coupled with any instability that develops from daytime heating of land could cause severe t-storms across the central US through the remainder of this weekend.

P2...Large upper trough spanning east Canada...the western Atlantic...and Caribbean persists. Eastern divergence of the upper trough has intensified a severe east Canada coast gale from 974 to 958 mb in the last 24 hrs while the gale has moved offshore toward southern Greenland. Expect rough seas in the Atlantic high seas...as well as high winds on the east coast of Canada...southern Greenland...and over open waters in the vicinity of this gale. Computer models agree that by 60 hours...a southern portion of the large upper trough should become cut-off...with the eastern divergence of the cut-off supporting a W Atlantic surface low. This W Atlantic surface low will be exposed to high SW vertical shear as the cut-off never closes off into an upper vortex...and the surface low will track northward quickly into cooler waters below 26 deg C. Therefore...this forecast surface low is not expected to develop into a subtropical cyclone.

P3...Deep-layered north Atlantic ridge...currently with a 1033 mb surface center...persists near the Azores.

P4...Eastern Atlantic upper trough is moving into western Europe. Eastern divergence of the upper trough supports surface cold front over western Europe mentioned in paragraph P2 of the previous discussion.

...TROPICAL BELT DISCUSSION...
P5...Upper ridge axis over the central tropical Atlantic persists. Upper divergence west of this upper ridge and east of the paragraph P2 upper trough continues to support a surface trough over the Lesser Antilles.

P6...Cut-off upper vortex NW of the Cape Verde Islands persists. Expansive upper divergence east of the upper vortex continues to support a large comma shaped t-storm area that continues overspreading the Cape Verde Islands and eastern tropical Atlantic. The surface low formerly supported by this same upper divergence in the previous discussion has continued westward while steered by 1033 mb ridge in paragraph P3. On this track...the surface low has continued westward across the south side of the upper vortex where westerly vertical shear is inhibiting it. It has also moved into dry sinking air supported by the western convergence of the upper vortex. As a result...the surface low has weakened into an inactive surface trough currently located midway between the Cape Verde Islands and Lesser Antilles.

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2012 Atlantic Hurricane Season Birdseye Discussion #156

By: NCHurricane2009, 4:42 PM GMT on November 10, 2012

...SATURDAY NOVEMBER 10 2012..11:42 AM EDT...
Subtropical cyclone development in the open eastern Atlantic now becoming less likely. See paragraph P6 for update statement on this system.

Computer models continue to agree that a surface low will develop in the western Atlantic in the timeframe that is now 84 hours. However the dynamics are not favorable for subtropical cyclone development as highlighted in paragraph P2.

Coastal weather conditions in areas hit by Hurricane Sandy days ago have vastly improved in the last 36 hours with the departure of the nor'easter as mentioned in paragraph P2.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...

This chart is generated based on surface analysis from the National Hurricane Center TAFB at 0600Z, and the 0726Z-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...The northern gale pushing across Canada's Hudson Bay in the previous discussion is entering NE Canada as a 1000 mb surface frontal low. The upper trough associated with this northern gale has merged with the north end of the upper trough in paragraph P2...with the western convergence of the upper trough supporting a 1035 mb central Canada surface ridge prior to the merger. The southern gale moving into the western US in the previous discussion is currently centered over southern Wyoming at 998 mb. Cold air from the 1035 mb ridge and moisture from the 998 mb southern gale continue to create winter weather...and winter storm warnings remain across Montana...North Dakota...and the higher elevations of the western US Rocky Mountains...with winter weather advisories across South Dakota and Nebraska. See www.nws.noaa.gov for latest info on the hazardous winter weather in these areas. Finally...low-level warm air advection ahead of the 998 mb southern gale supports a central US upper ridge. Eastern convergence of the upper ridge supports a 1026 mb eastern US surface ridge. Low-level southerlies between the 998 mb gale and 1026 mb ridge will be in directional shear with respect to upper westerlies across the central US upper ridge. The shear coupled with any instability that develops from daytime heating of land could cause severe t-storms across the central US through this weekend.

P2...Southern Greenland upper trough and associated surface gale near southern Greenland have crossed the NE Atlantic high seas while merging with the north end of the paragraph P4 upper trough. The cold front of the surface gale is marked in the upper-right corner of the above atmo chart located over western Europe. Elsewhere...the upper vortex over Massachusetts...the upper trough extending into the Caribbean...and the upper trough of the 1000 mb Hudson Bay low in paragraph P1...have all merged into one large upper trough spanning east Canada...the western Atlantic...and Caribbean. The 989 mb surface gale centered just offshore of Massachusetts in the previous discussion...a "nor'easter"...has pulled eastward further offshore in the last 36 hrs such that the weather conditions have vastly improved in coastal areas hit by Hurricane Sandy days ago. The "nor'easter" has weakened into a surface trough/cold front currently just SE of Newfoundland while it has continued to decay beneath the non-divergent axis of the upper trough. Meanwhile...eastern divergence of the upper trough has intensified the northern lobe of the dissipated nor'easter's low pressure field into a strong 974 mb gale on the east coast of Canada. Computer models agree that by 84 hours...a southern portion of the large upper trough should become cut-off...with the eastern divergence of the cut-off supporting a W Atlantic surface low. This W Atlantic surface low will be exposed to high SW vertical shear as the cut-off never closes off into an upper vortex...and the surface low will track northward quickly into cooler waters below 26 deg C. Therefore...this forecast surface low is not expected to develop into a subtropical cyclone.

P3...SW-NE tilted upper trough located SE of Newfoundland has become absorbed into the cut-off upper vortex of subtropical system to the southeast highlighted in paragraph P6. Deep-layered north Atlantic ridge...currently with a 1031 mb surface center...persists just SW of the Azores.

P4...Large eastern Atlantic upper trough persists. Eastern divergence of the upper trough continues supporting surface troughing over NW Africa.

...TROPICAL BELT DISCUSSION...
P5...Sprawling tropical Atlantic upper anticyclone has been split by massive paragraph P2 upper trough whose south end has amplified into the Caribbean Sea. The western split of the upper anticyclone is now an upper ridge axis over Costa Rica and the eastern Pacific. The eastern split of the upper anticyclone is now an upper ridge axis over the central tropical Atlantic. Upper divergence west of the central Atlantic upper ridge and east of the paragraph P2 upper trough supports a new surface trough over the Lesser Antilles.

P6...Cut-off upper vortex west of the Cape Verde Islands in the special feature section of previous discussion #155 has shifted NW while absorbing the SW-NE upper trough SE of Newfoundland mentioned in paragraph P3. Expansive upper divergence east of the upper vortex continues to support a large comma shaped t-storm area that has expanded into the Cape Verde Islands and eastern tropical Atlantic. This upper divergence has also intensified the associated surface trough into a 1012 mb low. Because this surface low and cloudiness is supported by a cold-core upper vortex...this system currently has the characteristics of a subtropical feature. The above-described NW shift of the upper vortex has placed the surface low in westerly vertical shear across the south side of the upper vortex...and therefore subtropical cyclone development is no longer expected from the surface low. As long as it survives...expect the surface low to continue tracking westward about the southern side of the paragraph P3 deep-layered ridge...then turn northward into the open Atlantic while influenced by the east side of forecasted W Atlantic surface low mentioned in paragraph P2.

Updated: 4:45 PM GMT on November 10, 2012

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2012 Atlantic Hurricane Season Birdseye Discussion #155

By: NCHurricane2009, 5:56 AM GMT on November 09, 2012

...FRIDAY NOVEMBER 9 2012..1:10 AM EDT...
Subtropical cyclone development in the open eastern Atlantic becoming more likely at a location west of the Cape Verde Islands. See the special feature section below for additional details.

Computer models also agree that a surface low will develop in the western Atlantic by 120 hours. However the dynamics are not as favorable for subtropical cyclone development as highlighted in paragraph P2.

Nor'easter continues impacting the coastal areas in the northeastern United States hit by last week's Hurricane Sandy as mentioned in paragraph P2.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...

This chart is generated based on surface analysis from the National Hurricane Center TAFB at 1800Z, and the 1917Z-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...EASTERN ATLANTIC SUBTROPICAL SYSTEM...
Southern half of paragraph P4 upper trough has cut-off into an upper vortex in relatively lower pressures south of the paragraph P3 deep-layered ridge. This upper vortex is currently centered west of the Cape Verde Islands in the open eastern Atlantic. Upper divergence on the NE quad of the upper vortex supports a well-organized and large comma shaped t-storm mass and associated new surface trough. Because this surface trough and cloudiness is supported by a cold-core upper vortex...this system currently has the characteristics of a subtropical feature. Meanwhile...the surface trough midway between the Cape Verde Islands and Lesser Antilles...supported by divergent upper northerly flow between this cut-off upper vortex and east end of the paragraph P5 upper anticyclone...and mentioned in paragraph P4 of the previous discussion...has dissipated.

Computer model runs of the CMC...GFS...and NOGAPS continue to support potential subtropical cyclone development from this system in what is now the 56 to 72 hr timeframe. However given the well-organized comma shaped cloud mass and developing surface trough...I have already upgraded this to a special feature as I believe the potential for development could occur sooner than this and as I believe the potential for development is becoming likely. Expect for the next days this system to first track westward about the southern side of the paragraph P3 deep-layered ridge...then turn northward into the open Atlantic while influenced by the east side of forecasted W Atlantic surface low mentioned in paragraph P2.

...MID-LATITUDES DISCUSSION...
P1...The large surface gale that entered western Canada and the western US in the previous discussion has split into two gales. The northern split and associated upper trough has pushed into Hudson Bay...with western convergence of the upper trough supporting a strong 1040 mb w Canada surface ridge not yet in the scope of the above charts. The southern split and associated upper trough is moving into the western US...with the pressure gradient between the southern gale and aforementioned 1040 mb ridge set to create gusty winds across Montana. The gusty winds and snow showers from the southern gale will create blizzard conditions across parts of Montana where blizzard warnings are in effect...with winter storm warnings in states adjacent to Montana. See www.nws.noaa.gov for info on the hazardous winter weather expected in parts of the western US. Finally...low-level warm air advection ahead of the southern gale supports western US upper ridge that has shifted into the central US. Eastern convergence of the upper ridge supports a 1025 mb eastern US surface ridge.

P2...Southern Greenland upper trough is beginning to advance eastward into the NE Atlantic high seas. Eastern divergence of the southern Greenland upper trough has intensified the associated surface gale from 988 to 983 mb. However...the gale should begin weakening now that it has whirled beneath the less-divergent axis of the upper trough. Western convergence of this upper trough supports 1031 mb east Canada surface ridge beginning to move offshore. Elsewhere...the NE North Carolina upper vortex has moved NE to Massachusetts...while the upper trough extending from the upper vortex to the Yucatan is now shifting into the NW Caribbean. The 996 mb gale centered just offshore of the US east coast...a "nor'easter"...continues to impact coastal areas hit by Hurricane Sandy with gusty winds and rain/snow showers. In the last 24 hours...the nor'easter intensified further to 989 mb thanks to continued support from the eastern divergence of the upper vortex now over Massachusetts. With the nor'easter whirling into a position beneath the upper vortex...it should begin weakening with a lack of divergence directly below the vortex. Computer models agree that by 120 hours...a southern portion of the upper vortex/trough should become cut-off...with the eastern divergence of the cut-off supporting a W Atlantic surface low. However unlike the above special feature in the eastern Atlantic...this W Atlantic surface low will be exposed to high SW vertical shear as the cut-off never closes off into an upper vortex...and the surface low will track northward quickly into cooler waters below 26 deg C. Therefore...this surface low is not expected to develop into a subtropical cyclone.

P3...SW-NE tilted upper trough located SE of Newfoundland persists. North Atlantic upper ridge in the previous discussion now thrives in supportive low-level warm air advection ahead of the nor'easter mentioned in paragraph P2. The north Atlantic surface ridge (currently 1032 mb) has become vertically stacked with the upper ridge such that a deep-layered ridge center is developing just SW of the Azores.

P4...Large eastern Atlantic upper trough persists. Eastern divergence of the upper trough continues supporting surface troughing over NW Africa and near southern Portugal. The development of the deep-layered ridge described in paragraph P3 has fractured the south end of this upper trough at a location W of the Cape Verde Islands. This fracture is currently associated with subtropical cyclone development potential...see the above special feature section for additional details.

...TROPICAL BELT DISCUSSION...
P5...Sprawling tropical Atlantic upper anticyclone continues covering the waters just east of the Lesser Antilles and the Caribbean Sea. As seen in the above thermo chart...dry air continues to whirling within the upper anticyclone...perhaps supported by converging upper northeasterlies on the SE half of the upper anticyclone. South-central Caribbean t-storms persist with the support of the outflow of the upper anticyclone.

Updated: 6:01 AM GMT on November 09, 2012

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2012 Atlantic Hurricane Season Birdseye Discussion #154

By: NCHurricane2009, 10:31 AM GMT on November 08, 2012

...THURSDAY NOVEMBER 8 2012..5:30 AM EDT...
Slight chance of subtropical cyclone development in the open eastern Atlantic remains possible as highlighted in paragraph P4 of the mid-latitudes discussion.

See paragraph P2 in the mid-latitudes discussion for statement on what is a strong nor'easter impacting the same coastal areas in the northeastern United States hit by last week's Hurricane Sandy.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...

This chart is generated based on surface analysis from the National Hurricane Center TAFB at 1800Z, and the 1920Z-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...Eastern lobe of gale offshore of the west coast of North America has crossed the US and has merged with nor'easter mentioned in paragraph P2. The associated shortwave upper trough...currently over central Canada...is merging and re-enforcing the paragraph P2 upper trough. Remaining west lobe of the gale has moved onshore into the western US and western Canada and is entering the upper-left corner of the above charts. Currently...warm air advection ahead of the gale supports west coast upper ridge that has shifted into the western US. Eastern convergence of the upper ridge supports a 1022 to 1023 mb central US surface ridge.

P2...Large-scale upper trough over the eastern US in the previous discussion currently consists of an upper vortex that has de-amplified into an upper trough while moving from the Maine/Canada border to southern Greenland. It also consists of an upper vortex over western North Carolina that has moved into NE North Carolina...as well as a shortwave upper trough over the southern Gulf of Mexico and Yucatan Peninsula. In the last 24 hours...eastern divergence of the southern Greenland upper trough has intensified the 994 mb Newfoundland surface frontal depression into 988 mb while moving NNE past the southern tip of Greenland. Western convergence of this upper trough supports 1029 mb east Canada surface ridge. Strong divergence on the east side of the NE North Carolina upper vortex has supported the rapid genesis of a surface non-tropical gale offshore of the US and along the front extending from what is now the 988 mb depression. This strong gale had already intensified to 996 mb as of last evening while tracking NE parallel to the US coast...and therefore it is called a "nor'easter." Unfortunately...the nor'easter is currently impacting coastal areas hit by last week's Hurricane Sandy with gusty winds and snow.

P3...Large upper trough pushing into the western Atlantic remains split into two SW-NE tilted upper troughs...one east of Greenland that has recently merged with the paragraph P4 upper trough...and the second remaining in the open central Atlantic located SE of Newfoundland whose south end now has an upper vortex. Relatively higher pressures between both upper troughs is currently where the north Atlantic upper ridge in the previous discussion thrives. Finally...the north Atlantic surface ridge (currently 1033 mb) remains supported by western convergence of the paragraph P4 upper trough.

P4...Large eastern Atlantic upper trough persists. Surface 1013 mb frontal depression over Morocco supported by the eastern divergence of this upper trough is now a 1015 mb depression near southern Portugal and a surface trough over Morocco. Low-level warm air advection ahead of what is a nor'easter mentioned in paragraph P2 will keep the north Atlantic upper ridge mentioned in paragraph P3 amplified...which has fractured the south end of this upper trough at a location W of the Cape Verde Islands. Upper westerlies flowing across this southern fracture heavily diverge with easterlies flowing into the paragraph P3 upper vortex...resulting in an impressive area of t-storms W of the Cape Verde Islands. This cluster of t-storms is also supported by the eastern upper divergence of this southern fracture. Upper divergence in split northerly flow between this southern fracture and east end of the paragraph P5 upper anticyclone supports a new surface trough midway between the Cape Verde Islands and Lesser Antilles. Computer model runs such as the CMC...GFS...and NOGAPS from last evening suggested the formation of a potential surface subtropical cyclone beginning in the 80 to 96 hr timeframe supported by eastern divergence of this southern fracture.

...TROPICAL BELT DISCUSSION...
P5...Sprawling tropical Atlantic upper anticyclone continues covering the waters just east of the Lesser Antilles and the Caribbean Sea. As seen in the above thermo chart...dry air continues to whirling within the upper anticyclone...perhaps supported by converging upper northeasterlies on the SE half of the upper anticyclone. In the last 24 hours...their has been an increase in south-central Caribbean t-storms supported by the outflow of the upper anticyclone.

Updated: 2:50 AM GMT on November 09, 2012

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2012 Atlantic Hurricane Season Birdseye Discussion #153

By: NCHurricane2009, 9:32 PM GMT on November 06, 2012

...TUESDAY NOVEMBER 6 2012...4:32 PM EDT...
Slight chance of subtropical cyclone development in the open eastern Atlantic remains possible as highlighted in paragraph P4 of the mid-latitudes discussion.

See paragraph P2 in the mid-latitudes discussion for statement on what appears to be an imminent threat of a nor'easter impacting the same areas in the northeastern United States hit by last week's Hurricane Sandy. Formation of this nor'easter is expected in the next 24 hours...and while it will bring gusty winds...it is not expected to be as severe as Hurricane Sandy. This nor'easter is not expected to gain tropical characteristics.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...

This chart is generated based on surface analysis from the National Hurricane Center TAFB at 1200Z, and the 1336Z-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...Eastern lobe of strong gale offshore of the west coast of North America has entered the upper-left corner of the above atmo chart from western Canada. Western lobe of the gale remains offshore. Currently...warm air advection ahead of both lobes supports highly-amplified west coast upper ridge whose eastern convergence supports a 1030 mb western US surface ridge. The back side of the eastern lobe is providing cool air advection...resulting in a shortwave upper trough diving SE from central Canada. In the next 24 hours....this shortwave upper trough will re-enforce the larger paragraph P2 upper trough...see paragraph P2 for how the re-enforced upper trough creates a nor'easter. It is then expected the remainder of the gale offshore of western North America will pivot into the western US in the wake of the nor'easter.

P2...Upper trough over the central US has moved into the eastern US... consisting of an upper vortex now over the Maine/Canada border and another upper vortex over western North Carolina. In the last 24 hours...eastern divergence of the upper trough has intensified the 1008 mb western Atlantic surface frontal depression into 994 mb while moving NE into Newfoundland. This same upper divergence has intensified a 1014 mb frontal depression into 1012 mb while it has moved ESE into the SE US. The depression was pushed ESE by the 1019 to 1024 mb surface ridge that has pivoted into the central US and eastern Canada supported by the western convergence of the upper trough. See statement in paragraph P1 on how this upper trough is expected to be energized by a shortwave upper trough from central Canada. In the next 24 hrs...the energized upper trough will support the rapid genesis of a surface non-tropical gale offshore of the Carolinas and along the front extending from what is now the 994 mb depression. This strong gale maybe what is now the 1012 mb SE US frontal depression...or alternatively this strong gale will absorb it. Either way the strong gale is expected to track NE parallel to the US coast...and therefore it will be called a "nor'easter." Unfortunately...the nor'easter is expected to impact areas hit by last week's Hurricane Sandy with gusty winds...with rain and snow showers also possible. However...this nor'easter is not expected to be as strong as Sandy.

P3...Large upper trough pushing into the western Atlantic has split into two SW-NE tilted upper troughs...one east of Greenland and a second in the open central Atlantic. 990 mb surface frontal depression over southern Greenland in the previous discussion has moved east with the first of the two upper troughs...and has weakened to 993 mb with a lack of divergence directly below the upper trough axis. Eastern divergence of the open central Atlantic upper trough supports widespread cloudiness. Relatively higher pressures between both upper troughs is currently where the north Atlantic upper ridge in the previous discussion thrives. Finally...the north Atlantic surface ridge (currently 1037 mb) has strengthened in the western convergence of the paragraph P4 upper trough.

P4...Large eastern Atlantic upper trough persists. Surface 1013 mb depression has moved ENE from the Canary Islands into Morocco in the last 24 hours. Low-level warm air advection ahead of what is expected to be a nor'easter mentioned in paragraph P2 will keep the north Atlantic upper ridge mentioned in paragraph P3 amplified...causing the east Atlantic upper trough to stay amplified east of the upper ridge axis...in turn strengthening western convergence on the back side of the upper trough axis such that the surface ridge currently in the north Atlantic (mentioned in paragraph P3) remains strong. In essence...the amplified north Atlantic upper ridge and strong surface ridge cuts-off a portion of the surface cold front extending from the 1013 mb low...and a portion of the east Atlantic upper trough...that all retrogrades westward such that subtropical cyclone formation is possible.

...TROPICAL BELT DISCUSSION...
P5...Sprawling tropical Atlantic upper anticyclone continues covering the waters east of the Lesser Antilles and the Caribbean Sea. Surface trough below the sprawling upper anticyclone...located midway between the Lesser Antilles and Cape Verde Islands...has dissipated in the last 24 hrs. As seen in the above thermo chart...dry air continues to whirling within the upper anticyclone.

Updated: 9:37 PM GMT on November 06, 2012

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2012 Atlantic Hurricane Season Birdseye Discussion #152

By: NCHurricane2009, 1:20 AM GMT on November 06, 2012

...MONDAY NOVEMBER 5 2012...8:20 PM EDT...
Slight chance of subtropical cyclone development in the open eastern Atlantic remains possible as highlighted in paragraph P4 of the mid-latitudes discussion.

See paragraph P2 in the mid-latitudes discussion for statement on what appears to be an imminent threat of a nor'easter impacting the same areas in the northeastern United States hit by last week's Hurricane Sandy. Formation of this nor'easter is expected at 48 hours...and while it will bring gusty winds...it is not expected to be as severe as Hurricane Sandy. This nor'easter is not expected to gain tropical characteristics.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...

This chart is generated based on surface analysis from the National Hurricane Center TAFB at 1800Z, and the 2013Z-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...Eastern lobe of strong gale offshore of the west coast of North America is entering the upper-left corner of the above atmo chart from western Canada. Western lobe of the gale remains offshore. Currently...warm air advection ahead of both lobes supports highly-amplified west coast upper ridge whose eastern convergence supports a western US surface ridge. For the next 48 hours...models show cold air driven in by the back side of the eastern lobe energizing the paragraph P2 upper trough. See paragraph P2 for how the energized paragraph P2 upper trough creates a nor'easter. The models then pivot the remainder of the gale into the western US in the wake of the nor'easter.

P2...Upper trough over the central US consists of an upper vortex now over SE Canada and upper trough extending to the SW. SE US 1013 mb surface frontal depression has moved offshore into the western Atlantic while intensifying to 1008 mb as the depression has taken advantage of eastern divergence of the upper trough. 1023 mb South Dakota surface frontal depression 24 hours ago has dived SE into Missouri while intensifying to 1014 mb in the same upper divergence. The depression was pushed SE by the 1023 to 1027 mb surface ridge from central Canada formerly supported by the western convergence of the paragraph P3 upper trough...and now supported by western convergence of this upper trough. See statement in paragraph P1 on how this upper trough is expected to be energized. By 48 hours...all models agree that strengthening upper divergence on the east side of the energized upper trough will support the rapid genesis of a surface non-tropical gale offshore of the Carolinas and along the front extending from what is now the 1008 mb depression. Because the strong gale is expected to track NE parallel to the US coast...it will be called a "nor'easter." Unfortunately...the nor'easter is expected to impact areas hit by last week's Hurricane Sandy with gusty winds...with rain and snow showers also possible. However...this nor'easter is not expected to be as strong as Sandy.

P3...Large upper trough pushing into the western Atlantic is now entirely offshore. Divergence on the east side of the upper trough supports 990 mb frontal depression that has lifted NNE from Newfoundland toward southern Greenland in the last 24 hours...while the 995 mb center approaching southern Greenland in the previous discussion has been absorbed by this 990 mb center. Low-level warm air advection ahead of the 990 mb center is supporting an upper ridge over the North Atlantic. North Atlantic surface ridge (currently 1035 mb) is strengthening in the western convergence of the paragraph P4 upper trough.

P4...Large eastern Atlantic upper trough persists. Surface 1011 mb depression south of the Azores in the previous discussion has moved ENE into the Canary Islands. Low-level warm air advection ahead of what is expected to be a nor'easter mentioned in paragraph P2 will keep the north Atlantic upper ridge mentioned in paragraph P3 amplified...causing the east Atlantic upper trough to stay amplified east of the upper ridge axis...in turn strengthening western convergence on the back side of the upper trough axis such that the surface ridge currently in the north Atlantic (mentioned in paragraph P3) remains strong. In essence...the amplified north Atlantic upper ridge and strong surface ridge cuts-off a portion of the aforementioned 1011 mb low and east Atlantic upper trough that all retrogrades westward such that subtropical cyclone formation is possible.

...TROPICAL BELT DISCUSSION...
P5...Sprawling tropical Atlantic upper anticyclone continues covering the waters east of the Lesser Antilles and the Caribbean Sea. Surface trough below the sprawling upper anticyclone...located midway between the Lesser Antilles and Cape Verde Islands...remains suppressed by dry air whirling within the upper anticyclone.

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2012 Atlantic Hurricane Season Birdseye Discussion #151

By: NCHurricane2009, 7:21 PM GMT on November 04, 2012

...SUNDAY NOVEMBER 4 2012...2:21 PM EDT...
Tropical cyclone development no longer possible in the southern Caribbean as highlighted in paragraph P5 of the tropical belt discussion. Slight chance of subtropical cyclone development in the open eastern Atlantic remains possible as highlighted in paragraph P4 of the mid-latitudes discussion.

See paragraph P2 in the mid-latitudes discussion for statement on what appears to be an imminent threat of a nor'easter impacting the same areas in the northeastern United States hit by last week's Hurricane Sandy. Formation of this nor'easter is expected at 72 hours...and while it will bring gusty winds...it is not expected to be as severe as Hurricane Sandy. This nor'easter is not expected to gain tropical characteristics.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...

This chart is generated based on surface analysis from the National Hurricane Center TAFB at 1200Z, and the 1411Z-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...Intense 960 mb gale that affected southern Alaska sits offshore of the west coast of North America and currently out of the scope of the above birdseye charts. Currently...warm air advection ahead of the gale supports highly-amplified west coast upper ridge whose eastern convergence supports a 1027 mb surface ridge over the western US. For the next 72 hours...models show an eastern lobe of the gale moving into western Canada and to the north of the western US surface ridge...with cold air driven in by the back side of the eastern lobe energizing the paragraph P2 upper trough. See paragraph P2 for how the energized paragraph P2 upper trough creates a nor'easter. The models then pivot the remainder of the gale into the western US in the wake of the nor'easter.

P2...Upper trough over the western US in the previous discussion has been pushed east into the central US thanks to building west coast upper ridge mentioned in paragraph P1. The upper trough consists of an upper vortex now over the Great Lakes and upper trough extending to the SW. The Texas/Oklahoma 1010 mb frontal depressions supported by the eastern divergence of this upper trough have shifted into the SE US as a now singular 1013 mb depression...while the 1020 mb depression over South Dakota in the previous discussion has been left behind and is weakening to 1023 mb in eastern convergence of the paragraph P1 west coast upper ridge. See statement in paragraph P1 on how the upper trough is expected to be energized. By 72 hours...all models agree that strengthening upper divergence on the east side of the energized upper trough will support the rapid genesis of a surface non-tropical gale offshore of the Carolinas and along the front extending from what is now the 1013 mb depression. Because the strong gale is expected to track NE parallel to the US coast...it will be called a "nor'easter." Unfortunately...the nor'easter is expected to impact areas hit by last week's Hurricane Sandy with gusty winds...with rain and snow showers also possible. However...this nor'easter is not expected to be as strong as Sandy.

P3...Large upper trough pushing into the western Atlantic...mentioned in paragraph P2 of the previous discussion...has arrived except for its northern portion still over SE Canada. Vast convergence west of the upper trough supports a 1020 mb ridge in the Gulf of Mexico and 1025 to 1031 mb ridge diving SE from central Canada. Divergence on the east side of the upper trough supports 996 mb frontal depression over SE Canada...which has lifted NNE toward southern Greenland while strengthening to 995 mb. Relatively new 996 to 997 mb surface frontal depressions just south of Atlantic Canada in the previous discussion...supported by the same upper divergence...have intensified into a singular 990 mb depression that has moved northward into Newfoundland. Low-level warm air advection ahead of these frontal depressions are supporting an upper ridge that has moved offshore into the north Atlantic from the east coast of Canada. North Atlantic surface ridge offshore of Canada (currently greater-than-1024 mb) is becoming supported by the western convergence of the paragraph P4 upper trough.

P4...Large eastern Atlantic upper trough at all latitudes persists. Surface 1000 mb vortex south of the Azores in the previous discussion has weakened to 1010 mb while trapped beneath the non-divergent upper trough axis. Meanwhile...upper divergence east of this axis meanwhile supports a western Europe surface front extending from the 1010 mb low. Low-level warm air advection ahead of what is expected to be a nor'easter mentioned in paragraph P2 will keep the north Atlantic upper ridge mentioned in paragraph P3 amplified...causing the aforementioned east Atlantic upper trough to stay amplified east of the upper ridge axis...in turn strengthening western convergence on the back side of the upper trough axis such that the surface ridge currently in the north Atlantic (mentioned in paragraph P3) strengthens. In essence...the amplified north Atlantic upper ridge and strengthening surface ridge cuts-off a portion of the aforementioned 1010 mb low and east Atlantic upper trough that all retrogrades westward such that subtropical cyclone formation is possible.

...TROPICAL BELT DISCUSSION...
P5...Sprawling tropical Atlantic upper anticyclone continues to have one anticyclonic center east of the Lesser Antilles and another over the Caribbean Sea. Shortly after previous discussion #150 was written...the central Caribbean surface trough strengthened into a 1009 mb surface low with t-storms thanks to upper outflow enhacement of the upper anticyclone. However...the 1009 mb low has been steered westward into central America via the easterly flow south of the Gulf surface ridge in paragraph P3. Since landfall...the surface low has lost its t-storm activity and identity within the ITCZ between 0600Z and 1200Z today...and therefore tropical development in the southern Caribbean is no longer expected. As of 1200Z...there is another surface trough that has entered the environment below the sprawling upper anticyclone...this one located midway between the Lesser Antilles and Cape Verde Islands which is the fracture of the old cold front extending south from the 1010 mb low in paragraph P4. However as we saw with the aforementioned failure of development in the southern Caribbean...a surface trough below an upper anticyclone does not mean imminent risk of tropical development. Plus...this surface trough is suppressed by dry air. An animation of the above thermo chart over the last days reveals this dry air originated on October 31 when the current 1010 mb low of paragraph P4 was a deep-layered low in paragraph P2 of discussion #148. Western upper convergence of the deep-layered low triggered the sinking dry air which has since been advected anticyclonically within the aforementioned sprawling upper anticyclone.

Updated: 1:07 AM GMT on November 06, 2012

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2012 Atlantic Hurricane Season Birdseye Discussion #150

By: NCHurricane2009, 3:14 PM GMT on November 03, 2012

...SATURDAY NOVEMBER 3 2012...11:30 AM EDT...
Tropical or subtropical cyclone formation is possible during the next days in two areas. See paragraph P4 in the tropical belt discussion for potential tropical cyclone development in the southern Caribbean. See paragraph P3 for potential subtropical cyclone development in the open eastern Atlantic.

...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...Next upper trough and surface frontal system in the mid-latitudes has entered the picture from the western US. The upper trough consists of an upper vortex over the Dakotas and upper trough over the SW US...and the surface frontal system consists of 1010 mb depressions in the Texas/Oklahoma area as well as a 1020 mb depression over South Dakota. Relatively warmer air ahead of these surface depressions supports a low-amplitude shortwave upper ridge over the central US.

P2...Broad surface frontal low in which Sandy became indistinct within during the previous discussion has lifted northward from SE Canada and out of the scope of the above birdseye charts. Meanwhile...upper vortex above this broad surface low has shifted eastward while merging with Great Lakes-to-Gulf of Mexico upper trough now heading into the western Atlantic. Vast convergence west of the upper trough/vortex supports a 1021 mb ridge in the Gulf of Mexico and 1028 mb ridge diving SE from central Canada. Divergence on the east side of the upper trough/vortex supports 1000 mb frontal depression near Newfoundland in the previous discussion...which has lifted northward into SE Canada while intensifying into 996 mb. This same upper divergence also supports new 996 to 997 mb surface frontal depressions just south of Atlantic Canada. Low-level warm air advection ahead of these frontal depressions are supporting an upper ridge over the east coast of Canada. Surface ridge offshore of Canada (currently 1025 mb) is becoming supported by the western convergence of the paragraph P3 upper trough.

P3...Upper vortex of deep-layered east Atlantic low south of the Azores is merging with NE Atlantic upper trough from paragraph P2 of the previous discussion to create one large upper trough across all latitudes of the eastern Atlantic. Meanwhile...the surface vortex of the former deep-layered low has weakened to 1000 mb while exposed to the non-divergent upper trough axis. Upper divergence east of this axis meanwhile supports a 1004 mb frontal depression moving into NW Spain...located along warm front extending from the 1000 mb low. Models over the last couple of days have shown that low-level warm air advection ahead of the paragraph P1 frontal system will re-amplify the paragraph P2 east Canada upper ridge...causing the aforementioned east Atlantic upper trough to re-amplify east of the upper ridge axis...in turn strengthening western convergence on the back side of the upper trough axis such that the surface ridge currently offshore of Canada (mentioned in paragraph P2) re-strengthens. In essence...the re-amplification of the east Canada upper ridge and strengthening surface ridge cuts-off a portion of the aforementioned 1000 mb low and east Atlantic upper trough that all retrogrades westward such that subtropical cyclone formation is possible.

...TROPICAL BELT DISCUSSION...
P4...Sprawling tropical Atlantic upper anticyclone now has one anticyclonic center east of the Lesser Antilles and another over the Caribbean Sea. T-storm activity has dwindled in association with the surface troughing in the central Caribbean Sea in the last 36 hrs. However because the upper anticyclone now overspreads the central Caribbean surface trough...this area will need to be monitored for potential tropical development. The track of this system depends on if and when development occurs...with ridge weaknesses to the NE favoring a more NE track...and surface ridges to the NW favoring a westward track. Cold fronts extending from the paragraph P2 upper troughing have created a ridge weakness to the NE...while the Gulf surface ridge in paragraph P2 persists to the NW while supported by convergence on the back side of the paragraph P2 upper troughing. Models then eject the paragraph P2 upper trough NE...and likewise the Gulf surface ridge supported on the back side of the upper trough. Quickly...the models eject the paragraph P1 upper trough eastward in place of the paragraph P2 upper trough such that its western convergence re-builds a Gulf surface ridge to the NW...and eastern divergence of this upper trough re-creates another surface ridge weakness to the NE.

P5...Relatively higher pressures southeast of the paragraph P3 upper trough supports upper ridge near the Cape Verde Islands.

P6...Surface ridge toward the west coast of Africa (currently 1015 to 1017 mb) remains weak due to upper divergence on the east of the paragraph P3 upper trough overspreading the area.

Updated: 9:33 PM GMT on November 03, 2012

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2012 Atlantic Hurricane Season Birdseye Discussion #149

By: NCHurricane2009, 8:31 AM GMT on November 02, 2012

...FRIDAY NOVEMBER 2 2012...4:35 AM EDT...
Tropical or subtropical cyclone formation is possible during the next 120 hours (5 days) in two areas. See paragraph P4 in the tropical belt discussion for potential tropical cyclone development in the southern Caribbean. See paragraph P2 for potential subtropical cyclone development in the open eastern Atlantic.

...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).

...MID-LATITUDES DISCUSSION...
P1...The remnant surface low of Sandy continues weakening below non-divergent upper vortex while in SE Canada...and as of 1925Z November 1 became indistinct within a broader surface frontal low pressure. Cut-off upper trough (left behind by the upper vortex) over the SE US/Gulf of Mexico has merged with upper trough moving across the Great Lakes. Vast convergence west of the merged upper trough supports Gulf of Mexico and SW US surface ridging. Divergence on the east side of the upper vortex supports new 1000 mb frontal depression near Newfoundland...with low-level warm air advection ahead of the depression supporting an upper ridge over east Canada that was formerly the north Atlantic upper anticyclone supported by stronger warm air advection ahead of what was Sandy. Surface ridge offshore of Canada (currently 1020 mb) is becoming supported by the western convergence of the paragraph P3 upper trough.

P2...Deep-layered low pressure system/upper vortex persists in the eastern Atlantic at a location south of the Azores. Even though this system is centered over mild water temps of 23 to 24 deg C...t-storm activity persists with this system...which indicates the cold core upper vortex of the system is cold enough for instability over these water temps. 120-hour outlook of this system is complex...with the system currently trapped southeast of deep-layered ridging consisting of both the east Canada upper ridge and surface ridge offshore of Canada both mentioned in paragraph P1. As the remnant of Sandy has dissipated...the associated low-level warm air advection ahead has weakened such that the east Canada upper ridge has de-amplified...currently allowing this deep-layered low to shift east while merging with the paragraph P3 upper trough. However by the end of 120 hours...all models agree that low-level warm air advection ahead of the next frontal system will re-amplify the east Canada upper ridge...causing the paragraph P3 upper trough to re-amplify east of the upper ridge...in turn strengthening western convergence on the back side of the paragraph P3 upper trough such that the surface ridge currently offshore of Canada re-strengthens. In essence...the re-amplification of the east Canada upper ridge and strengthening surface ridge cuts-off a portion of the deep-layered low that retrogrades westward such that subtropical cyclone formation is possible once again if the current deep-layered low does not develop.

P3...Upper trough in the NE Atlantic persists in relatively lower pressures east of the the E Canada upper ridge in paragraph P1.

...TROPICAL BELT DISCUSSION...
P4...Sprawling tropical Atlantic upper anticyclone is now centered over the northern Lesser Antilles. Upper divergence on the NW quad of the upper anticyclone continues supporting central Caribbean surface troughing. T-storm activity has become less organized around the surface troughing in the last day while becoming exposed to SW vertical shear from the paragraph P1 upper troughing. This increase in shear was predicted by the GFS model yesterday...but the models soon allow the favorable tropical Atlantic upper anticyclone to rebuild over the surface trough. Although their is no computer model support for development...the potential overspreading of the favorable upper anticyclone suggests potential for tropical development. The track of this system depends on if and when development occurs. Over the next 120 hours...their will be surface ridge weaknesses that will try to draw the system east...and surface ridges that try to draw the system west. Models agree that cold fronts extending from the paragraph P1 upper troughing will first create a ridge weakness to the NE...while the Gulf surface ridge in paragraph P1 persists to the NW while supported by convergence on the back side of the paragraph P1 upper troughing. Models then eject the paragraph P1 upper trough NE...and likewise the Gulf surface ridge supported on the back side of the upper trough. Quickly...the models come in with the next frontal upper trough before 120 hours is over...with western convergence of this upper trough re-building a Gulf surface ridge to the NW...and eastern divergence of this upper trough re-creating another surface ridge weakness to the NE.

P5...Relatively higher pressures southeast of the paragraph P2 deep-layered low supports upper ridge near the Cape Verde Islands.

P6...1015 mb ridge north of the Lesser Antilles in the previous discussion is eroding while becoming exposed to upper divergence SE of the paragraph P1 upper troughing and NW of the paragraph P4 upper anticyclone. Surface ridge toward the west coast of Africa (currently 1013 mb) remains weak due to upper divergence on the SE quad of the paragraph P2 deep-layered cyclone overspreading the area.

Updated: 9:23 PM GMT on November 03, 2012

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2012 Atlantic Hurricane Season Birdseye Discussion #148

By: NCHurricane2009, 3:27 AM GMT on November 01, 2012

...WEDNESDAY OCTOBER 31 2012...11:30 PM EDT...
The remnant gale of Sandy has continued to weaken while drifting northward into southeastern Canada...and is no longer producing significant weather. The Appalachian Mountains in West Virginia remain under a winter weather advisory...see www.nws.noaa.gov for hazards associated with this advisory.

Elsewhere...tropical or subtropical cyclone formation is possible during the next 120 hours (5 days) in two areas. See paragraph P4 in the tropical belt discussion for potential tropical cyclone development in the southern Caribbean. See paragraph P2 for potential subtropical cyclone development in the open eastern Atlantic.

...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...The remnant surface low of Sandy continues weakening below non-divergent upper vortex. The surface low and upper vortex are shifting northward into SE Canada about the east side of the central US upper trough finally pushing into the Great Lakes. The upper vortex has left behind an upper trough over the SE US and Gulf of Mexico that is merging with central US upper trough. Vast convergence west of both upper troughs supports Gulf of Mexico and SW US surface ridging. Immense low-level warm air advection ahead of Sandy's large circulation continues supporting a large north Atlantic upper anticyclone. Surface ridge offshore of Canada (currently 1025 mb) is becoming supported by the western convergence of the paragraph P3 upper trough...and surface ridge also persists over Hudson Bay in Canada.

P2...Deep-layered low pressure system/upper vortex persists in the eastern Atlantic at a location south of the Azores. Even though this system is centered over mild water temps of 23 to 24 deg C...t-storm activity has become stronger and better organized in the last 24 hours...which indicates the cold core upper vortex of the system is cold enough for instability over these water temps. Therefore...the NHC tropical weather outlook may soon flag this area...and I may release a special update in between full blog updates if this system proceeds toward subtropical cyclone formation. 120-hour outlook of this system is complex...with the system currently trapped southeast of deep-layered ridging consisting of both the north Atlantic upper anticyclone and surface ridge offshore of Canada both mentioned in paragraph P1. As the remnant of Sandy has continued to weaken...the low-level warm air advection ahead of the remnants has weakened such that the north Atlantic upper anticyclone should soon de-amplify...allowing this deep-layered low to shift east while merging with the paragraph P3 upper trough. However by the end of 120 hours...all models agree that low-level warm air advection ahead of the next frontal system will re-amplify the north Atlantic upper anticyclone...causing the paragraph P3 upper trough to re-amplify east of the upper anticyclone...in turn strengthening western convergence on the back side of the paragraph P3 upper trough such that the surface ridge currently offshore of Canada re-strengthens. In essence...the re-amplification of the north Atlantic upper anticyclone and strengthening surface ridge cuts-off a portion of the deep-layered low that retrogrades westward such that subtropical cyclone formation is possible once again if the current deep-layered low does not develop.

P3...Upper trough in the NE Atlantic persists in relatively lower pressures east of the the north Atlantic upper anticyclone in paragraph P1. Currently its eastern divergence supports a 1005 mb surface frontal depression over Morocco along the warm front extending from the paragraph P2 deep-layered low.

...TROPICAL BELT DISCUSSION...
P4...Sprawling east-west tropical Atlantic upper anticyclone is now centered over the northern Lesser Antilles. Upper divergence on the NW quad of the upper anticyclone continues supporting Caribbean surface troughing that has shifted from the eastern to the central Caribbean. T-storm activity has become better organized around the surface troughing while under the favorable outflow of the tropical Atlantic upper anticyclone..and although their is no computer model support for development...this favorable upper wind config is shown in the models to last for the next 120 hours. Therefore...this area should be watched for tropical development...and the track of this system depends on if and when development occurs. Over the next 120 hours...their will be surface ridge weaknesses that will try to draw the system east...and surface ridges that try to draw the system west. Models agree that cold fronts extending from Sandy and the paragraph P1 upper troughing will first create a ridge weakness to the NE...while the Gulf surface ridge in paragraph P1 persists to the NW while supported by convergence on the back side of the paragraph P1 upper troughing. Models then eject the paragraph P1 upper trough NE...and likewise the Gulf surface ridge supported on the back side of the upper trough. Quickly...the models come in with the next frontal upper trough before 120 hours is over...with western convergence of this upper trough re-building a Gulf surface ridge to the NW...and eastern divergence of this upper trough re-creating another surface ridge weakness to the NE.

P5...Relatively higher pressures southeast of the paragraph P2 deep-layered low supports relatively new upper ridge near the Cape Verde Islands mentioned in paragraph P4 of the previous discussion.

P6...Surface trough heading toward the Lesser Antilles has been removed from TAFB maps...but interestingly their is a t-storm complex on satellite imagery SE of the Lesser Antilles. Tropical latitude surface troughing in the vicinity of the cold front of the paragraph P2 deep-layered low persists. 1016 mb ridge west of the surface troughing and NE of the Lesser Antilles has weakened to a 1015 mb center north of the Lesser Antilles while becoming exposed to upper divergence SE of the paragraph P1 upper troughing and NW of the paragraph P4 upper anticyclone. 1012 mb ridge to the east of the surface troughing and toward the west coast of Africa has weakened to 1011 mb due to upper divergence on the SE quad of the paragraph P2 deep-layered cyclone overspreading the area.

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