Weatherdem's Weblog

Bridging climate science, citizens, and policy

Atlantic Tropical Weather Update 8/18/09 #3

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The first major hurricane of the 2009 Atlantic season is Hurricane Bill.  Here are his vitals as of tonight:

Center located at 17.2N, 53.4W; moving WNW @ 14mph; maximum sustained winds of 125mph; minimum central pressure of 952mb, which is a drop of ~10mb since earlier this afternoon.

The drop in central pressure means that further strengthening is likely for Hurricane Bill.  He is a strong Category-3 storm right now.  The threshold between Category-3 and Category-4 storms is 130mph.  As such, the NHC has revised its official intensification forecast: by tomorow morning at 8A EDT, Hurricane Bill should be a Category-4 storm.  That condition is likely to last through Friday, with cyclical weakening and strengthening as the storm begins to replace eye-walls.

The official track forecast takes Hurricane Bill north of 30N by late Friday night, meaning Bermuda is in for a rough Saturday morning.  Given the relatively high latitude, decreasing ocean heat content and increasing wind shear, Hurricane Bill should begin to permanently weaken after Friday night.  By Saturday night, Bill is forecasted to be due east of North Carolina as a Category-3 storm.  By Sunday night, Bill is now forecasted to be due south of Nova Scotia, Canada as a Category-2 storm.  Thereafter, Bill is likely to keep decaying and taking on extra-tropical characteristics.

Some ensemble model solutions take Bill ashore near Connecticut.  Others take him ashore on New Brunswick, Nova Scotia or far-east Quebec.  All of them take Bill across the north Atlantic before possibly impacting the British Isles next week.  The landings near CT, NB, NS or Quebec are unlikely solutions.  They are possible, however, so the storm should remain in folks’ interest until it has passed you by.

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