Tropical Storm Isaac:

Wednesday, August 22, 2012 5:45 am by Rob Lightbown of Crown Weather

Isaac is clearly intensifying this morning based on satellite imagery and reconnaissance reports. Very deep thunderstorm activity has been firing in all quadrants of the storm for better than six hours now. Reconnaissance aircraft have found that the central pressure has fallen to 1003 millibars. Further intensification is expected today and residents and vacationers across all of the islands of the Leeward Islands need to be prepared for 50 to 60 mph sustained winds with gusts to hurricane force from late this morning through this afternoon and into tonight.

Isaac is tracking nearly due west at a forward speed of 16 to 17 mph this morning. This westward track is expected to continue right into Friday and Saturday. After that, a trough of low pressure over the central United States is forecast to strengthen causing the strong ridge of high pressure to Issac’s north to weaken and decay on its western side. This, in turn, will cause Isaac to turn to the northwest. How far west in longitude Isaac gets in the next 2 to 3 days will ultimately determine its final track as it approaches the US coastline early next week.

As for the latest forecast guidance: The track guidance forecasts that Isaac will first track across Guadeloupe by this evening, then just south of Puerto Rico on Thursday afternoon and evening before tracking across southern and western Haiti on Friday and headed for the Bahamas and southeast Florida by Sunday and Monday. Now, for the global model guidance:

The GFS model forecasts a track that takes Isaac across the island of Guadeloupe this evening and then across southern and western Haiti, as well as across eastern Cuba from Saturday into Sunday. After that, the GFS model forecasts that Isaac will track right along the spine of the Florida Peninsula from Monday into Tuesday.

The European model guidance forecasts a track that takes Isaac just south of Hispaniola and across Jamaica before tracking through the Yucatan Channel and into the Gulf of Mexico early next week. In the end, the European model forecasts that Isaac will impact central and southeastern Louisiana right around the end of next week. It should be pointed out that the European model forecasts a significantly weaker storm in the Caribbean as compared to the GFS model.

I think the latest European model guidance is way too far west and do think that Isaac will make a northwestward turn, especially since it is currently undergoing intensification as I write this. It should be pointed out that the Canadian model guidance is further to the east than the GFS model and forecasts a strengthening hurricane to impact southeastern North Carolina on Monday. The latest GFDL and HWRF models forecast a track that takes Isaac right along Florida’s east coast on Sunday.

So, my thinking as of this morning is as follows:
I do think that Isaac will track right over Guadeloupe by this evening and then track just south of Puerto Rico during Thursday afternoon and evening. After that, I think we will see Isaac turn more northwestward and come across western Haiti and eastern Cuba during Saturday. Once Isaac is past Cuba, I expect it to continue on a northwestward course and track along a line from about Miami to Orlando to Gainesville on Monday into Monday evening as at least a Category 1 hurricane. After tracking right along the spine of Florida, I think we will see Isaac track right into the inland portions of eastern Georgia, eastern South Carolina and central North Carolina by about the middle part of next week.

Tropical storm force winds are expected to impact much of the Leeward Islands this afternoon into tonight. Wind gusts of near hurricane force seem likely, especially given the fact that Isaac is strengthening this morning. Total rainfall amounts of up to 8 inches are likely across the Leeward Islands from Isaac.

As for Puerto Rico and the Virgin Islands: Strong tropical storm force winds with gusts to hurricane force are likely across the Virgin Islands during the day Thursday and across Puerto Rico from Thursday afternoon into Thursday night. Total rainfall amounts of up to 6 inches are expected from Isaac across Puerto Rico and the Virgin Islands.

All residents and vacationers in the Leeward Islands, Virgin Islands and Puerto Rico need to be prepared for tropical storm conditions. Additionally, all residents and vacationers across the Florida Peninsula and the Bahamas need to keep very close tabs on the forecast track of this system. Go over your hurricane preparedness kits today and make sure you know what to do should hurricane conditions impact Florida and the Bahamas early next week.

I am monitoring the progress of Isaac very closely and will continue to update you on the latest.

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