Tuesday, September 20, 2005

Readin' Rita

Sometime between 1pm and 2pm, the official Washington temperature hit 90 degrees for the 6th time this month. Humidity has also increased, with dewpoints in the low to mid 60s. Some showers which developed near Annapolis around mid afternoon have spread into a broken line from the Maryland middle Eastern Shore across the lower Potomac to the Northern Neck of Virginia and towards Richmond. Easton, MD reported a heavy thunderstorm around 3:45 and precipitation of 0.20". There is nothing to the west which would bring some relief for our developing drought.

Tonight and Tomorrow

The chances of an isolated shower developing through this evening are only about 10%. Lows will be in the mid 60s under clearing skies. Tomorrow will be sunny with highs in the mid 80s and lower humidity.

Tropical Beat

After remaining a tropical storm overnight, Rita quickly strengthened into a hurricane this morning. It is now a Category 2 storm with max winds of 100 mph. At 5pm, the center was about midway between Key West and Havana, moving west at about 15 mph. Key West was recently reporting an east wind at 41 kt, gusting to 50. Hurricane warnings are in effect for the Florida Keys and for the coast of Florida from Florida City on the east around to Chokoloskee on the southwest coast. Tropical storm warnings are also in effect for portions of the Florida coast northward to Jupiter Inlet on the east and Englewood on the west. Rita is expected to strengthen further as it makes its way into the Gulf of Mexico.

Rita's future path depends on the behavior of a huge ridge of high pressure which was stretching this afternoon in the middle of the atmosphere (500 mb level) from Arizona all the way across to the southeastern U.S. coast. (Notice the big area enclosed by the line labeled 594 and the unusual 600 line enclosing the peak of the ridge over Texas.) This had actually strengthened a little from this morning, but it also shifted to the east. The ridge will weaken as a low-pressure trough now off the California coast moves eastward, but the main factor will be a second trough developing over the West Coast toward the end of the week. If that trough is deep enough, it will force the steering currents over the Gulf to be more from the south, and the hurricane will take a more easterly path, perhaps as far east as western Louisiana. Otherwise, it could move into the southern Texas coast or possibly even northern Mexico.

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