08 June 2005

First Tropical Depression forms in western Caribbean...

An Air Force aircraft flew a recon mission into the system this afternoon, reaching it at about 4pm EDT and found a closed circulation, making it TD1.  The low-level center is located at 17.2N 84.0W.  Convection is not very centralized, but outflow aloft is improving in all quadrants.  Initial intensity measured by the aircraft is 25kts and 1004mb.

The vertical wind shear has relaxed to 15kts and is still decreasing as the subtropical jet lifts out of the area.  The SSTs are about 29C there, and the 26C water is roughly 100m deep (26C is the rule-of-thumb threshold for tropical cyclogenesis), so there is ample energy available to it even if it stalls for a bit.  The warm water is much shallower in the Gulf, so once there it must move more quickly to avoid cool upwelling.

The forecast is still for gradual strengthening and drifting north toward the US coastline.  Timing and location are the key questions, but the canned answer I'll give is "it's too early to know for sure".  Most likely is on Saturday between New Orleans and Appalachicola as tropical storm.

Please visit my tropical Atlantic headquarters.

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