2012 Atlantic Hurricane Season Birdseye Discussion #47
...JULY 9 2012...10:02 PM EDT...
Still Watching thunderstorm activity along frontal boundary...associated with deep-layered cyclone in Northwestern Atlantic (see paragraph P2). Chances for the next African tropical wave to develop have diminshed (see paragraph P11).
...ATMOSPHERIC FEATURES BIRDSEYE CHART...
This chart is generated based on surface analysis from the National Hurricane Center TAFB at 1800Z, and the 1923Z-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...Strong upper ridge over North America has weakened due to cool air advection behind NW Atlantic cyclone in paragraph P2. Westerly warm air advection south of the same cyclone has spread this upper ridge eastward into the western Atlantic. Upper convergence on the south side of this upper ridge supports a 1018 mb surface ridge in the Gulf of Mexico.
P2...Northwest Atlantic surface cyclone remains centered over eastern Canada with surface center of 992 mb as of 1923Z. Now that the surface center has whirled beneath the less divergent core of its supporting upper vortex (which has recently opened into a longwave upper trough)...expect the surface center to begin weakening. Upper convergence behind the longwave upper trough supports a 1024 mb surface ridge in NE North Dakota. Split flow upper divergence between the SW edge of the longwave upper trough and north edge of the upper ridge in paragraph P1 supports t-storms...a long surface front...and frontal depressions across the east half of the US...all trailing from the surface cyclone. If this trailing front and t-storm activity sags southward into the favorable low shear/enhanced outflow of the upper ridge in paragraph P1...then tropical development in the norhwest Atlantic could be possible in the next days.
P3...NE Atlantic upper trough persists. Cut-off upper trough in the middle of the Atlantic left behind by this system has re-merged with it.
P4...Open Atlantic surface ridge still has a strong center...currently just west of the Azores...which is supported by upper convergence on the back side of the NE Atlantic upper trough (paragraph P3).
...TROPICAL BELT DISCUSSION...
P5...Central America upper ridge persits. T-storm activity supported by the outflow of this upper ridge has reduced now that the tropical wave in paragraph P9 has exited into the eastern Pacific.
P6...Caribbean upper vorticity has elongated into a few features while wedged between the Central America upper ridge in paragraph P5...eastern Caribbean upper ridge in paragraph P7...and North America upper ridge in paragraph P1. This upper vorticity now consists of an upper low in the southern Gulf of Mexico...an upper trough over the Bahamas...with split flow divergence at the boundary between these two features supporting a new surface trough/t-storms near south Florida. This upper vorticity also has an upper vortex in the south Caribbean...and yet another upper vortex south of Bermuda.
P7...Eastern Caribbean upper ridge persists with an anticyclonic center just northeast of the area.
P8...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. Single inverted upper trough on the south side of this upper ridge persists.
P9...Tropical wave crossing the southern Gulf of Mexico and Bay of Campeche in the previous discussion is now exiting the picture while moving into SE Mexico and eastern Pacific. Therefore...this is the last discussion of this tropical wave on this blog.
P10...Tropical wave approaching the northern Caribbean islands in the previous discussion is currently crossing Puerto Rico and the waters to the north. It remains suppressed by dry air mentioned in paragraph P8...and is encountering additional unfavorable conditions thanks to westerly vertical shear from the upper vorticity in paragraph P6.
P11...Tropical wave east of the Cape Verde Islands in the previous discussion has now crossed the islands...and is now just west of the islands. It is rolling into dry air mentioned in paragraph P8. It has failed to sustain enough t-storm activity to expand the east end of the upper ridge in paragraph P8 with latent heat release. Had it been able to do so...the tropical wave would have pushed off the inverted upper trough to the west such that the inverted trough would act as an enhanced outflow channel. It is now also entering the unfavorable upper convergent environment directly below this inverted upper trough.
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