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Atlantic Tropical Weather Update 9/5/08

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[Update 12P MDT]:

For informational purposes: Tropical Storm Hanna is approaching Category 1 hurricane strength.  It means little except for official designations and statistics.  The reality is Hanna’s sustained wind speed have increased by 5mph to 70mph.  The difference at landfall between a strong tropical storm and a weak Category 1 hurricane is negligible.  The outer rain band of Hanna is now making its way across the Carolinas.

New model runs that started this morning became available.  I’m not sure if it’s good or bad news for the U.S.  Instead of making landfall along the southern Florida coast, Hurricane Ike’s projected path has flattened out somewhat and it now appears more likely that he will brush by either Cuba or Florida Tuesday on his way into the Gulf of Mexico.  The official track forecast splits the difference and moves Ike through the Florida Strait as a Category 4 storm.  Once in the Gulf, Ike could weaken to a Category 3 storm as he contends with cooler waters.  If the ridge guiding Ike’s motion remains strong through the weekend and into early next week, Ike could wait to turn towards the northwest and north until he’s in the eastern Gulf.

***

A couple of important changes are available to discuss this morning with regard to the storms currently in the Atlantic.

The first storm to talk about is Tropical Storm Hanna. Her vitals as of this morning:

Center located at 28.2N, 78.2W; maximum sustained winds of 65mph; moving NW @ 18mph; minimum pressure of 980mb. So T.S. Hanna’s pressure has dropped slightly overnight. It won’t be enough to cause the storm to intensify to hurricane status, due to the dry air Hanna continues to entrain. Her track forecast has shifted overnight. Instead of making landfall over the coast of North Carolina, Hanna is now expected to come ashore over near the North Carolina/South Carolina border again either very late tonight or very early tomorrow morning as a tropical storm.

As a result, the official track forecast moves Hanna a little to the left of the official track presented yesterday. She should pass south of Washington D.C., but is also likely to impact New York City and Boston by Sunday morning, albeit as a weaker and very fast moving system. Surge impacts will remain as a threat to coastal areas. Up to 5″ of rain is expected over a wide area of coastal locations from South Carolina to Massachusetts.

Hurricane Ike has weakened slightly overnight, as was expected. Here are his vitals this morning:

Center located at 23.7N, 61.0W; maximum sustained winds of 125mph; moving W @ 14mph; minimum pressure of 945mb.

Ike’s northwestward motion, again as correctly forecasted, has shifted to a more due westerly motion. The 125mph winds mean Hurricane Ike is again a Category 3 storm. In the next 24 hours, Ike should begin moving more toward the WSW or SW as the ridge to his north strengthens. By this time tomorrow, Ike is officially forecasted to weaken to a Category 2 storm until he finally leaves the northeasterly shear behind. During the day on Saturday, however, Ike is forecasted to regain his Category 3 status due to 29C sea surface temperatures and a weak shear environment.

Ike’s motion after Saturday night remain pretty uncertain. A lot depends on how strong the ridge to his north is and where it sets up. By Sunday morning, Ike is still expected to be bearing down on the southeastern Bahamas. Sometime during Sunday afternoon or night, Ike’s official forecast indicates a curve back to the west, then the west-northwest. Further intensification is identified during this time period, and by Monday morning, Ike could again be a Category 4 storm racing through the central Bahamas. The curvature to his track could very slowly increase toward the north in the 4-5 day range. Ike is currently forecasted to finish moving through the Bahamas by Tuesday morning and could threaten south Florida Tuesday night or very early Wednesday morning. Compared to last nights model runs, Ike’s track has shifted southward across Florida. Last night, Miami looked like it was going to be the site of landfall. This morning, it looks like the southern tip of Florida could be that site, which would unfortunately put Miami on the right (more powerful) side of a major hurricane.

I’ll say again that the exact location of the storm in the 4-5 day range is incredibly questionable. But two consecutive model envelopes have put Florida in Ike’s path at the end of the period. However, Ike could just as easily make landfall over Cuba, as two models are showing, or could turn toward the north before striking Florida, as another model shows. As we go through the weekend, Ike’s potential U.S. impacts will become more clear.

Tropical Storm Josephine has battled some southerly shear overnight and it shows this morning.  Her convection is now displaced from the center and she has weakened.  Her vitals:

Center located at 15.8N, 34.8W; maximum sustained winds of 45mph; moving WNW @ 8mph.

T.S. Josephine will continue moving generally toward the NW over the 5 day forecast period.  The next two days will prove critical for Josephine’s existence.  If she can survive the shear currently present, she could stay alive.  If she doesn’t, she will be reduced to a disturbance that will have to wait to move further west before potential redevelopment.

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