02 August 2012

Tropical Depression 5 forms

At 21Z yesterday (5pm EDT), the easterly wave we've been talking about was upgraded to a Depression.  There's a bit of fuzziness involved with the exact transition, but some key features to look for are a closed surface circulation and persistent centralized deep convection.  The central pressure is down to 1008mb, and is located at approximately 13N 53W (~550 miles east of the Lesser Antilles) and cruising westward at 15kts.  It is expected to reach the central Lesser Antilles late on Friday, and I will hopefully have a radar loop available from Martinique as it passes through the area.

TD5 is also now entering a more data-rich part of the basin, with buoys, islands, and later today, aircraft.  Buoy 41040 is located about 100 miles due north of TD5's center, and is reporting 30kt gusts and 9' waves.  There is another buoy in its path (41101), so that will also provide some key intensity observations during its closest approach in about 12 hours.

Although it's still over 28C water, it has found itself in an unexpectedly hostile shear environment.  There's currently about 20kts of shear over the system, which disrupts whatever warm core might be trying to form, and allows for enhanced entrainment of environmental drier air.  So it's struggling a bit, and probably will for another 2-3 days, which is very good news for the Lesser Antilles... they're no stranger to monster hurricanes plowing through, making this a welcome change.

As far as the track forecast goes, there's a bit of spread in the models, but they generally agree on a trek across the Caribbean, so Hispaniola, Jamaica, Cuba, etc should be watching this VERY closely.  Once this becomes a tropical storm (sustained winds reach 35kts), the next name on the list is Ernesto.

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