2012 Atlantic Hurricane Season Birdseye Discussion #44
...JULY 6 2012...2:15 PM EDT...
Eastern Caribbean tropical wave still not expected to develop (see paragraph P10 for details). Northwestern Atlantic disturbance has been absorbed by deep-layered 1000 mb cyclone (paragraph P1). Next strong tropical wave is emerging from west coast of Africa (paragraph P12).
...ATMOSPHERIC FEATURES BIRDSEYE CHART...
This chart is generated based on surface analysis from the National Hurricane Center TAFB at 1200Z, and the 1334Z-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).
P1...While continuing eastward around the central North America upper ridge...diffuse 1002 mb cyclone over the NE US has moved into the northwest Atlantic as a deep-layered 1000 mb cyclone...and this deep-layered cyclone is moving northward around the surface ridge in paragraph P4...hence tracking toward Atlantic Canada and toward waters temps in the teens of deg C too cool for subtropical development. Remainder of the deep-layered cyclone's upper trough is moving toward the west coast of Greenland with a new 1008 mb cyclone it supports. Cut-off upper trough over the Tennesee valley has moved southward over the SE US coast while orbiting the central North America upper ridge. While continuing to zoom east across the north side of the upper ridge...south-central Canada frontal cyclone and its upper trough now has a 997 mb surface center over E Hudson Bay. The cold front trailing from this south-central Canadian cyclone features a 1008 mb depression and t-storm complex supported by upper divergence on the NW quadrant of the upper ridge. Finally...upper convergence on the east side of the upper ridge is supporting the 1018 mb ridge in the eastern Gulf of Mexico and SE US.
P2...Complex frontal system covering the northern half of the Atlantic Ocean has all made landfall in western Europe (marked with upper trough and extratropical surface low in the upper-right corner of the above charts). It left behind a west Atlantic upper trough 24 hrs ago that was getting absorbed by the upper-layers of the deep-layered 1000 mb cyclone in paragraph P1. Whatever did not get absorbed is now a cut-off upper trough in the middle of the Atlantic...wedged between the east Caribbean upper ridge in paragraph P8 and east Atlantic upper ridge in paragraph P9.
P3...Cut-off upper vortex southwest of the Azores has moved northward toward upper troughing of the system in paragraph P2...and is now west of the Azores.
P4...Open Atlantic surface ridge still has a strong center....currently just north of the Azores...which is supported by upper convergence on the back side of the upper troughing pushing into Europe (paragraph P2).
...TROPICAL BELT DISCUSSION...
P5...Inverted upper trough over the Bay of Campeche and western Gulf of Mexico is retrograding slowly west into south Texas and NE Mexico while orbiting the strong central North America upper ridge mentioned in paragraph P1.
P6...Upper ridge over Central America has gained concentration near the Panama area...where t-storm activity and associated latent heat release has been strongest in the last 24 hours. Surface convergence from the tropical wave in paragraph P10 may be enhancing the Panama area t-storm activity.
P7...Central Caribbean upper vorticity has gained east-west stretch while wedged between the Central America upper ridge in paragraph P6...eastern Caribbean upper ridge in paragraph P8...and North America upper ridge in paragraph P1.
P8...Eastern Caribbean upper anticyclonic ridge persists. Its upper outflow had supported extensive t-storm activity for the tropical wave in paragraph P10 24 hours ago...which has since left the area. The remnant debris clouds of this t-storm activity are now anticyclonically turning about this upper ridge.
P9...Expansive east Atlantic upper ridge continues. In conjunction with the surface ridge in paragraph P4...deep-layered easterly flow exists across much of the Atlantic tropics that is advecting African desert dry air (brown shading in the above thermo birdseye chart) westward. Inverted upper trough signatures on the south and east sides of this east Atlantic upper ridge continue...one of which has closed off into an upper low W of the Canary Islands that could retrograde southwestward around the upper ridge in the next days...or altenratively get absorbed by upper troughing currently pushing into Europe (paragraph P2).
P10...Tropical wave crossing the eastern Caribbean in the previous discussion is now in the central Caribbean. As expected...the tropical wave has finally become suppressed by upper vorticity in paragraph P7. The only development potential I see is near the Panama area...where the tropical wave is enhancing t-storm activity beneath a divergent Central America upper ridge (paragraph P6)...especially if that upper ridge expands in the wake of gradually collapsing upper vorticity in paragraph P7. Not seeing signs of this occurring at this time. Although shear is low in the Gulf of Mexico...thanks to deep-layered easterlies on the south side of the upper ridge and 1018 mb surface ridge in paragraph P1...a look at the models shows the upper vorticity in paragraph P7 retrograding westward into the Gulf of Mexico...and therefore I expect the tropical wave to remain suppressed by upper convergence beneath this upper vorticity as the tropical wave continues toward the Gulf of Mexico.
P11...Tropical wave west of the Cape Verde Islands in the previous discussion is now midway between the Cape Verdes and Lesser Antilles. This tropical wave is in favorable low shear thanks to deep-layered easterly flow mentioned in paragaraph P9...but is suppressed by dry air also mentioned in paragraph P9.
P12...Satellite imagery suggests the next strong tropical wave is about to emerge from the west coast of Africa (as remarked in the lower-right corner of the above charts). If the tropical wave in paragraph P11 is a good analogue...then dry air should ultimately prevent this wave from developing. However...I am watching how this tropical wave phases with new upper low located west of the Canary Islands...mentioned towards the end of paragraph P9. If this upper low retrogrades southwestward...then it could enhance the poleward upper outflow of this tropical wave...allowing it to fight against the dry air.