24 June 2012

Debby forms in northern Gulf, threatens the coast

On Saturday at 21Z (5pm EDT), the disturbance in the Gulf was upgraded to Tropical Storm Debby based primarily on aircraft recon into the system.  On average, we only see the 4th named storm on August 23, and to have the 4th named storm form on June 23 shatters the previous record set by Dennis on July 5, 2005.  This is truly a remarkable season so far!  As of 12Z on Sunday, Debby is located about 200 miles south of Pensacola FL and drifting north at 2kts, with a slowwww turn to the west expected later today.  The maximum sustained winds are 50kts and the minimum surface pressure is 994mb.  Debby is forecast to continue intensifying, and perhaps reach hurricane status by mid-week.


There are tropical storm warnings in place along a large stretch of the northern Gulf coast, as shown here.  There is larger-than-normal uncertainty in the track forecast due to the very weak steering currents and wildly divergent model guidance, but the latest official forecast shows a westward drift for the next couple of days, then speeding up a little but still heading generally west toward TX or western LA.  Keep in mind that the size of the cone of uncertainty is fixed for a season, and does not reflect storm-specific uncertainties.


The biggest threat from Debby right now is the large amount of rain.  The forecast rainfall over the next 5 days is shown here, with the largest amount offshore, but substantial amounts over land.  Several oil rigs in the Gulf have already begun evacuations and are shutting down, and some coastal counties/parishes have declared a state of emergency.


Being so close to the coast does have one advantage... constant monitoring by land-based radars.  The latest composite shows the extent of the rain, and you can always view the most recent loop at http://radar.weather.gov/Conus/southeast_loop.php


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