2012 Atlantic Hurricane Season Birdseye Discussion #125

By: NCHurricane2009 , 7:24 AM GMT on October 06, 2012

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...OCTOBER 6 2012...3:30 AM EDT...
The text in this discussion is about 48 hours after previous discussion #124. The birdseye view charts below are about 36 hours after those in previous discussion #124.

An outage persists with GOES-E satellite imagery in the last several days. GOES-W has been extended to cover much of the view in the two birdseye charts below. However...the east edge of the GOES-W scan has a bias for showing cold cloud tops that are not actually present. Therefore...I have patched the east side of the atmospheric birdseye chart with Meteosat-9 grafts. The east side of the thermodynamics birdseye chart is left unrepaired...so be mindful that the moisture content on the east side of this chart has a positive bias due to the false illusion of cold cloud tops.

Nadine and Oscar have become remnant systems as previously anticipated. See paragraphs P6 and P13 for update statements on the remnants of these two tropical cyclones.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...

This chart is generated based on surface analysis from the National Hurricane Center TAFB at 1800Z, and the 1912Z-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 from W Canada has amplified significantly into an upper vortex currently over south-central Canada...thanks to impressive cold air advection from strong surface ridge over the central US and W Canada it supports with its western convergence...and thanks to cold air advection from frontal depression its supports with its eastern divergence. This frontal depression was 1004 mb over the central US in the previous discussion...and now is still 1004 mb while whirling into south-central Canada beneath the upper vortex. A 1000 mb frontal depression is just to the east...formerly the Great Lakes surface cyclone in paragraph P2 of previous discussion #124...and now supported by eastern divergence of the upper vortex.

P2...Major upper trough from central North America remains split into a few features ahead of the paragraph P1 upper vortex. Western convergence of the southernmost split is driving dry air over the SW US and W Gulf of Mexico...and a 1018 mb surface ridge over Arizona. The eastern divergence of a shortwave upper trough over Atlantic Canada is driving a batch of clouds over Newfoundland. The eastern divergence of northernmost shortwave upper trough (not seen in above atmo chart) continues driving a surface cold front eastward across southern Greenland (cold front marked in top-center of above atmo chart)...and western convergence of this same upper shortwave drives 1020 mb surface ridge just offshore of Newfoundland. Southerly flow from the paragraph P8 W Atlantic upper ridge converges with the westerly flow ahead of the upper troughs mentioned in this paragraph...this upper convergence driving a surface 1020 mb ridge over the eastern US.

P3...A surface 1010 mb low is marked just north of Bermuda this early morning...which is a decay of the old cold front associated with surface cyclone from the Great Lakes mentioned in paragraph P1 above (and mentioned in paragraph P2 of previous discussion #124).

P4...Deep-layered cyclone has moved east-southeast from offshore of Atlantic Canada and into the central Atlantic while its upper trough dug SE to the east of the paragraph P8 W Atlantic upper ridge. Surface center of the cyclone strengthened from 992 to 984 mb since previous discussion #124...as the surface center continues to tap into eastern upper divergence of the upper trough. This strong surface cyclone is centered west of the Azores this early morning.

P5...Based on Meteosat-9 animation over the last 48 hours...upper trough has moved into western Europe and out of the scope of the above atmo chart. However...the same satellite animation suggests a second shortwave upper trough is pivoting southeastward on the back side of the previous upper trough...also headed toward western Europe and marked in upper-right corner of above atmo chart. Western convergence of the upper trough activity in this area continues driving NE Atlantic surface ridge.

P6...Since previous discussion #124...Nadine became extratropical (non-tropical) while moving NE across the Azores and into the open NE Atlantic. Satellite animation of Meteosat-9 over the last 48 hours suggests the remnant of Nadine became very well-defined while receiving supportive upper divergence from the east side of the paragraph P4 upper trough. The remnant is recently becoming less-defined in Meteosat-9...but Meteosat-9 suggests the remnant is turning eastward toward the British Isles while hitching a ride with paragraph P5 upper shortwave currently heading toward W Europe.

...TROPICAL BELT DISCUSSION...
P7...Central tropical Atlantic upper vortex persists...while its old SW fragment retrograded about paragraph P7 W Atlantic upper ridge and is now a central Caribbean upper vortex near Jamaica. As both upper vortices gradually weaken (as all cut-off upper vortices do)...a southern Caribbean upper ridge is building in their wake...and a W Caribbean upper ridge has also built in relatively higher pressures between the Jamaica upper vortex and southernmost upper trough in paragraph P2. Yet another upper ridge persists in relatively higher pressures east of these upper vortices...located across the eastern tropical Atlantic. Upper outflow of the aforementioned southern Caribbean upper ridge supported t-storms across the south-central Caribbean...Panama..Costa Rica...and a portion of the eastern Pacific...but these t-storms have recently dwindled.

P8...W Atlantic upper ridge persists while supported by low-level warm air advection ahead of the paragraph P1 1000 mb frontal cyclone that moved from the Great Lakes into south-central Canada. Split flow upper divergence between south edge of this upper ridge and north edge of paragraph P7 central tropical Atlantic upper vortex supports a batch of t-storms and a developing surface trough south of Bermuda.

P9...A surface trough is currently in the southern Gulf of Mexico and Bay of Campeche...which is a decay of the old cold front associated with surface cyclone from the Great Lakes mentioned in paragraph P1 above (and mentioned in paragraph P2 of previous discussion #124). T-storm activity of the surface trough is supported by eastern divergence of southernmost upper trough mentioned in paragraph P2 above...but SW vertical shear from the same upper trough is preventing tropical development from this feature.

P10...Tropical wave moving into the eastern Caribbean in the previous discussion is now entering the central Caribbean.

P11...NHC TAFB recently added a tropical wave moving across the Lesser Antilles since the previous discussion. I suspect this tropical wave originated from Africa and was too poorly-defined for TAFB to mark it until recently. Eastern divergence from paragraph P7 central tropical Atlantic upper vortex is assisting in creating t-storms. While the t-storms have recently become curved and better organized at a location just NE of the Lesser Antilles...this organization is occurring about the upper vortex rather than the surface tropical wave.

P12...By continuing to track a westward-moving cluster of t-storms using Meteosat-9 infrared satellite...I have continued marking a suspect tropical wave which I believe this early morning is positioned in the open tropical Atlantic to the south of Oscar's remnant.

P13...As expected...Tropical Storm Oscar in the eastern tropical Atlantic turned eastward in westerly flow on south side of the paragraph P4 deep-layered cyclone...and is no longer a tropical cyclone while its low pressure field loses its identity in the vast low pressure field of the cyclone. It is worth noting that the NHC track and intensity forecast in previous discussion #124 did very well...while my track and intensity forecast during that time has larger error.

P14...NHC TAFB has added a tropical wave that has recently moved offshore from Africa..marked just SE of the Cape Verde Islands. Meteosat-9 shows associated t-storm cluster just south of the Cape Verde Islands.

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