Stephen's Tropical Storm Gustav Blog

By: Stephen Bowers Email
By: Stephen Bowers Email

I'll start with a general discussion of Tropical Storm Gustav, and for the weather enthusiasts like myself, I will go into a little more detail after the more general discussion.

General Discussion
Tropical Storm Gustav will likely continue on a slow track toward the west across the northern Caribbean Sea. By Thursday afternoon or evening, a gradual turn more toward the northwest is anticipated and that is expected to continue across most of the expanse of the Gulf of Mexico.

There is the possibility that Gustav will continue northward or north-northwestward and have some direct impact along the coast of southeast Louisiana, Mississippi, Alabama, or the western Florida Panhandle. As of Wednesday afternoon, the most likely impact zone looks to be along the coast between Lafayette, LA and Pensacola, FL. Please note that this forecast is several days out, and a lot may change between Wednesday afternoon and the time of landfall.

Occasionally, I will have disagreements with the forecast track from the National Hurricane Center, although I will always show their official forecasts on air. Often, I also agree with the official forecast, and this is one of the times I do agree with their forecast track. Intensity forecasts are a little more difficult, but right now the official intensity forecast also seems reasonable to me.

National Hurricane Center's Forecast

Detailed Discussion
Tropical Storm Gustav made landfall yesterday afternoon along the south coast of Haiti. Following that landfall, Gustav has been moving very slowly between west and northwest. One of the main reasons for that northwest movement yesterday was a weakness in the high pressure area to the north that was caused by an upper level low pressure system that has moved well east of Gustav this afternoon. As the high pressure remains anchored over the Bahamas, Gustav will continue westward since is embedded within the clockwise flow and south of the high pressure's center.

That area of high pressure extends across Florida and into the Gulf of Mexico, and most models indicate some west to east erosion of that high pressure zone as an upper level trough of low pressure drops southward from the U.S. Plains states. This will set up a general south to north or south-southeast to north-northwest flow across the central Gulf of Mexico.

The upper level low pressure trough that is eroding the ridge may play in the favor of most. It's possible that the trough may dig farther south and give Gustav a bit of a shove more toward the northeast. I don't necessarily expect that, and the models have not picked up on that possibility just yet. If that should happen, I would expect that the wind shear, or change of wind, that would nudge the storm northeastward would also help to weaken Gustav a bit - and that's where it plays in everyone's favor.

One major concern I have is the loop current eddy that is situated over the central Gulf of Mexico. Most forecast models as well as the official forecast track from the National Hurricane Center move Gustav over this eddy, and typical fashion is that storms go through a process called rapid intensification when crossing this warm water eddy. Most major storms I can think of were not major storms until they reached this feature. A few past storms that passed over a similar eddy that come to mind are Katrina, Rita, and Opal. Intensity forecasts range from 90 mph to 145 mph as Gustav crosses the Gulf. The official forecast from the National Hurricane Center does bring the storm to category 3 intensity.

The major thing to remember is that no place on the Gulf Coast is in the clear yet. There's still almost a week for things to change and come together.

I'll discuss more of the potential effects of Gustav over the next couple of days when the confidence of the forecast is a little higher.

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