...APRIL 26 2012...
This partial discussion is issued as a special update concerning a potential tropical disturbance developing in the central Caribbean Sea.
During the previous week, an unusually late winter storm extratropical cyclone dumped heavy snow in western New York State and Pennsylvania. Since then, the associated large upper trough and associated surface cold front has emerged into the western Atlantic. Showers and thunderstorms have been gradually increasing across the central Caribbean Sea as the upper trough/surface cold front interacts with the surface North South American monsoon/ITCZ.
Upper-level flow is both southwesterly and divergent in advance of the large upper trough. The divergent aspect of the upper flow...coupled with surface convergence from the surface cold front & ITCZ/north South American monsoon...are repsonsible for the activity presently in the central Caribbean. The southwesterly aspect of the upper flow is shearing the disturbance. However if latent heat release continues with these thunderstorms...the upper flow could become more anticyclonic as a warm core upper ridge develops overhead. If this were to occur...this would enhance the outflow and reduce the vertical shear...and a tropical disturbance would be very likely. Should this happen...I will be re-issuing full birdseye discussions.
In the short term...expect the upper southwesterly flow to transport moisture from this disturbance northeastward...bringing rains to Jamaica...eastern Cuba...Haiti...and the Dominican Republic.