2012 Atlantic Hurricane Season Birdseye Discussion #15A (Special Update)
...MAY 23 2012...
Early tropical activity persists in the Atlantic basin! The Naval Reasearch Laboratory (NRL) of the United States Navy has upgraded an area of disturbed weather in the western Caribbean Sea to Invest 94-L.
This disturbance has been several days in the making as a browse through previous discussions shows:
Second special feature section of discussion #12
Paragraph P6 of discussion #13
Paragraphs P7 and P8 of discussion #14
Paragraph P7 of discussion #15
The prognosis for this disturbance had been that it would not develop due to exposure under westerly vertical shear on the north side of Caribbean upper ridging. The upper ridge was expected to remain suppressed to the south (and maintain the shearing) due to (a) the upper vorticity near Tropical Storm Alberto and (b) the next upstream frontal upper trough behind this upper vorticity.
Shortly after full discussion #15 was written...the lowest surface pressures in the western Caribbean were able to collocate with the Caribbean upper ridge axis...and the system became a little better organized with T-storm banding features E of the low surface pressures. T-storm activity west of the low surface pressures remains absent due to the persistence of aforementioned westerly vertical shear.
The upper vorticity near what was once Alberto has been absorbed by the next upstream frontal upper trough...as this frontal system moves into the eastern US. The first challenge this system faces is surviving the impulse of westerly vertical shear on the south side of this frontal upper trough.
The second challenge is adjacent dry air that has been persisting in the Gulf of Mexico and northern Florida over the last several days (for example see discussion #15...paragraph P5 for the source of this dry air). If the low surface pressures spin up into a cyclone...the cyclonic circulation could easily ingest this dry air source.
Prognosis this early morning is to watch this system carefully...and see how well it fares against the above two challenges. If I see signs of tropical cyclone formation...I will once again be resuming pre-season full birdseye discussions. If not...this will be the last until June 1 2012. Regardless...the presence of this disturbance will continue rains in the western Caribbean (Honduras...Nicaragua...Cayman Islands...Jamaica...Cuba) and Bahamas over the next days. Some of these areas have been saturated by the persistent rainfall with this sytem...so flooding is another possibility.