Disorganized 99L Headed for FL

Thursday 25 August

Disturbance 99L remains highly disorganized this morning. Although convective flareups overnight have been impressive, much of the thunderstorm activity has developed well away from the center. A favorable upper ridge aloft is too far south over Hispaniola to aid in development at this time. Instead, westerly shear and dry air are likely to inhibit significant development for at least another 24 hours. Beyond 24 hours, there is considerable disagreement among model guidance as to whether atmospheric conditions will improve. There is a possibility that an upper low approaching from the northeast may allow for conditions to become only marginally conducive before the slowly-developing disturbance passes over southern Florida.

Despite a slight westward shift within the tropical model suite over the last six hours, there is a fairly good consensus up the Florida peninsula among the more dynamical models. A southwestward retrograding upper low underneath a ridge centered over the Carolinas may lower atmospheric heights near FL just enough to draw 99L between Apalachicola and Orlando. A trof moving eastward between the Midwest US and Great Lakes would also aid in a northerly turn. A track very near, or close to the length of the FL peninulsa would hinder substantial intensification.

Despite everything outlined above, the degree of intensification 12-24 hours prior to passage over south Florida is the primary forecast question mark and concern. Latest data suggests development will be marginal, but a disturbance moving over extremely high oceanic heat content is always an eye opener.