2012 Atlantic Hurricane Season Birdseye Discussion #147

By: NCHurricane2009 , 8:27 AM GMT on October 31, 2012

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...WEDNESDAY OCTOBER 31 2012...4:27 AM EDT...
The remnant gale of Sandy over the northeastern United States has continued to weaken...with weather conditions improving except for in the Appalachian Mountains where blizzard and winter storm warnings remain in effect. See paragraph P1 of the mid-latitudes discussion for update statement on the remnant of Sandy.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...

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

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

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

...THERMODYNAMICS BIRDSEYE CHART...

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

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

...MID-LATITUDES DISCUSSION...
P1...The remnant surface low of Sandy has orbited westward across southern Pennsylvania about the north side of the cut-off upper vortex previously to its southwest...and in turn low-level cool air wrapping around the west and south sides of Sandy has made the cold core upper vortex shift east then NE about Sandy's south side. Recently...the upper vortex and surface low have become vertically stacked such that the surface low of Sandy continues weakening beneath the non-divergent upper vortex. However...the Appalachian Mountains continue to be socked by snow and gusty winds...as the higher elevations are exposed to the portion of Sandy's circulation not limited by surface friction. Central US upper trough mentioned in paragraph P1 of the previous discussion will soon shift into the Great Lakes and pull Sandy and the upper vortex northward. Vast convergence west of this upper trough 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. 1038 mb surface ridge on the east coast of Canada has weakened to an offshore 1031 mb ridge stacked below the upper anticyclone...and a surface ridge over Hudson Bay in Canada.

P2...Deep-layered low pressure system/upper vortex persists in the central Atlantic is shifting into the eastern Atlantic. At the surface...their continues to be a broad low pressure spin in the low 990s of mb that has whirled into a position beneath the upper vortex.

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 couple of surface frontal depressions near southern Spain along the warm front extending from the paragraph P2 deep-layered low.

...TROPICAL BELT DISCUSSION...
P4...Sprawling east-west tropical Atlantic upper anticyclone remains centered just NE of the Lesser Antilles. Upper divergence on the NW quad of the upper anticyclone continues supporting a surface trough extending from south of Sandy into the NW Caribbean...which has evolved into a cold front extending from Sandy..as well as continued surface troughing and new t-storms in the eastern Caribbean Sea. SW-retrograding upper vortex near the Cape Verde Islands in the previous discussion has opened into an upper trough W of the Cape Verde Islands while getting drawn into the south side of the paragraph P2 deep-layered low. Relatively higher pressures east of this upper trough supports a new upper ridge near the Cape Verde Islands.

P5...Surface troughing midway between the Cape Verde Islands and the Lesser Antilles has split into one surface trough heading toward the Lesser Antilles...and another surface trough becoming assimilated into the cold front extending from the paragraph P2 deep-layered cyclone. 1013 mb ridge west of the surface troughing and NE of the Lesser Antilles has strengthened to 1016 mb while taking advantage of upper convergence on the NE side of the paragraph P4 upper anticyclone. 1016 mb ridge to the east of the surface troughing and toward the Cape Verde Islands has weakened to 1012 mb due to upper divergence on the SE quad of the paragraph P2 deep-layered cyclone overspreading the area.

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