Westward Shift Continues on Isaac

NEW: South Florida will face Isaac's lashing Sunday as the eastern side of the storm will bring the potential for tornadoes and flooding rains. The SPC has placed most of the South Florida in a slight risk for severe weather, including the likelihood of tornadoes in Isaac's outer bands:

After killing 3 in Haiti, Tropical Storm Isaac is now tracking back over open water, parallel to the north coast of Cuba and is heading towards the Florida Straits. By Sunday afternoon, this system will solidly be in the Gulf of Mexico, where rapid intensification seems very likely.

If you've been following Isaac closely, you know that the latest trends in the models have favored a farther track west, suggesting a central Gulf Coast landfall early next week (LA, MS, AL). Notice the 00z model runs shifted even farther west, targeting the SE Louisiana coast for a landfall:

Isaac's track really depends on the upper air pattern evolving over the US- the ridge building over the four corners region and the trough developing over the eastern half. The trough will have the most influence on Isaac; if the trough is deeper and farther south, this will likely 'grab' Isaac and lure the storm more northeast, which would mean a landfall farther east- likely the Florida panhandle as was previously thought. However, if the trough is flatter and stays farther north, Isaac will likely stay on its NW track and likely move into Louisiana.

The European model, which originally was an outlier with the farthest west landfall, is is now showing Isaac tracking closer to the FL/AL state line, near Pensacola Tuesday night:

-photo courtesy of Garrett Bedenbaugh

The image above is valid Tuesday at 7PM.

The GFS has shifted farther west with each run today, and now suggest Isaac will make landfall along the SE Louisiana coast Tuesday evening:

The Canadian solution is very close the the GFS in respect to location, but is 6 hours slower; below is valid at 1AM Wednesday morning, showing Isaac near the mouth of the MS River:

How strong will Isaac be? That answer may be a bit troubling. First, let me show you the HWRF 00z run. This model is suggesting Isaac will strengthen into a major category 4-5 hurricane before making landfall near Port Sulphur, LA, Tuesday afternoon:

This seems to be one of the faster models and is probably too fast- but the agreement with the Canadian and GFS on location cannot be ignored. This model has one of the most bullish intensity forecasts, but with the upper air pattern over the Gulf favoring development and warmer than normal water temperatures, this cannot be ignored!

Here again, is the *official* forecast from the National Hurricane Center, suggesting Isaac will make landfall near Fort Walton Beach, Florida, late Tuesday night into Wednesday. It is important not to focus solely on the center line as the effects of Isaac will be felt for hundreds of miles around the storm center, especially if this thing becomes a major hurricane:

Stay tuned for further updates!