2012 Atlantic Hurricane Season Birdseye Discussion #53
...JULY 15 2012...11:35 PM EDT...
It appears tropical wave has lost its chances of developing east of the Lesser Antilles (see paragraph P10). New pop-up disturbance east-southeast of Bermuda showing no signs of developing in the midst of high surface pressures (see paragraph P6).
...ATMOSPHERIC FEATURES BIRDSEYE CHART...
This chart is generated based on surface analysis from the National Hurricane Center TAFB at 1800Z, and the 1930Z-released HPC analysis.
In light blue is upper air analysis, with 200 mb wind barbs calculated by GOES satellite imagery showing the upper-level wind direction. Based on the 200 mb wind barbs, blue-dashed lines are locations of upper troughs, blue-zig-zag lines are locations of upper ridges. Blue Ls are locations of upper lows, blue Hs are locations of upper ridges.
In red is surface analysis, with solid lines indicating locations of surface fronts, dashed lines indicating locations of surface troughs, and zig-zag lines indicating surface ridge axes. Ls indicate surface lows, Hs indicate surface highs.
...THERMODYNAMICS BIRDSEYE CHART...
This chart is generated using GOES water vapor satellite imagery. Brown indicates dry air. White, blue, and purple indicates moist air. An increase in moisture indicates slower air parcel lapse rates with elevation and hence an increase toward instability.
Sea-surface temperatures are overlaid with light blue isotherms. The 26 deg C isotherm is highlighted in red. Waters at and south of the 26 deg C isotherm indicate low-level warmth and hence faster environmental lapse rates with elevation (more instability). Waters north of the 26 deg C isotherm indicate slower environmental lapse rates with elevation (less instability).
...MID-LATITUDES DISCUSSION...
P1...Hudson Bay frontal system and its supporting upper trough are beginning to shift east. Likewise...the east North America upper ridge supported by warm air advection ahead of this frontal system is shifting east. Whatever of the upper trough and upper ridge that is not shifting east is now a cut-off upper vortex over Texas and cut-off upper anticyclone over the SE US. Upper convergence behind the upper trough supports a 1019 mb ridge over central Canada...and upper convergence behind the Texas cut-off upper vortex supports a 1019 mb ridge over the SW US.
P2...Surface 998 mb cyclone south of Greenland and its upper trough are beginning to shift eastward toward Europe. Although the surface cyclone has not yet weakened...expect this to happen any time now as it is beneath the less divergent axis of the upper trough. Upper convergence on the back side of this upper trough is supporting a 1019 mb ridge over Newfoundland.
P3...Cut-off upper vortex SW of the Azores has opened into an upper trough as it begins merging with upper trough mentioned in paragraph P2.
P4...Open Atlantic surface ridge has dissolved into multiple centers from the eastern US all the way toward Europe without a clear-cut upper convergent source to support a dominant surface ridge center. In conjunction with the south side of the upper ridge in paragraph P7...south side of this surface ridge is helping to waft Africa desert dry air westward across the Atlantic tropics.
...TROPICAL BELT DISCUSSION...
P5...Upper ridge covering the south half of the Caribbean Sea has produced a blow-up of t-storms over E Honduras...E Nicaragua...and Costa Rica with a divergent upper anticyclonic center.
P6...Caribbean area upper vorticity has all shifted into the southern Gulf of Mexico...and extends to a new upper vortex offshore of the Carolinas. The eastern inflow of this upper vorticity has been diverging heavily with the western inflow of the cut-off upper vortex in paragraph P3...the divergence resulting in widespread cloudiness from near Bermuda all the way to Florida...and resulting in a new surface trough over Bermuda and the waters SW that has now moved into Florida. This Florida surface trough is now supported by divergence between the upper vortex in the south Gulf and upper vortex offshore of the Carolinas. There is also a new upper ridge just NE of Bermuda that separates this upper vorticity from the upper vortex in paragraph P3...and this upper ridge has recently expanded into the Bahamas. The outflow of this upper ridge has created a circular t-storm burst ESE of Bermuda and weak surface trough. Because the weak surface trough is in the midst of high surface pressures of the ridge in paragraph P4...and because the surface trough is located east rather than under the circular storm burst...I do not expect tropical cyclone development. Louisiana coast surface trough has dissipated...but its southward west Caribbean extension that formed yesterday has moved into the southern Gulf of Mexico while now supported by divergence between the south Gulf upper vortex and cut-off Texas upper vortex in paragraph P1.
P7...East Atlantic upper ridge persists...still featuring an anticyclonic center WNW of the Cape Verde Islands that has begun a southwestward shift predicted by computer models...thanks to the merger between the paragraph P3 upper vortex and upper trough in paragraph P2 that is pushing the anticyclonic center. Disorganized upper vorticity is still located west of the anticyclonic center...toward the Lesser Antilles and E Caribbean Sea. Upper trough from Canary Islands has shifted southward to the Cape Verde Islands while orbiting the east side of the anticyclonic center.
P8...Tropical wave in the eastern Caribbean is moving into the central Caribbean. It is suppressed by southwesterly vertical shear induced by the upper vorticity mentioned in paragraph P6.
P9...Tropical wave midway between the Cape Verdes and Lesser Antilles is now nearing the Lesser Antilles. It is suppressed by dry air mentioned in paragraph P4.
P10...Satellite animation suggests there is still a possible tropical wave SW of the Cape Verde Islands. This is the third time I have analyzed this wave in the above birdseye charts while the NHC TAFB maps have yet to acknowledge it...so my confidence in the existence of this tropical wave is decreasing. If this tropical wave has existed...continued northerly shear on the east flank of the upper anticyclonic center in paragraph P7 has allowed the dry air in paragraph P4 to intrude from the north. Paragraph P7 explains that the upper anticyclonic center is shifting southwest as the models have been predicting...which would mean eventual vertical alignment with this tropical wave...and hence good upper outflow enhancement. However...the expanse of the dry air intrusion now tells me tropical cyclone development is out the window despite the potential for upper outflow enhancement in the future.
P11...Satellite imagery suggests yet another tropical wave is rolling off the coast of Africa. I am gun shy to add this possible tropical wave to the above birdseye charts until if/when NHC TAFB adds the tropical wave in paragraph P10 to their charts. The upper trough headed toward the Cape Verde Islands in paragraph P7 may enhance the western upper outflow of this possible tropical wave...but dry air (in paragraph P4) is likely to be a challenge as it has been for the past several tropical waves.
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