2012 Atlantic Hurricane Season Birdseye Discussion #161

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

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...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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