The Threat Invest 95L Poses to the Gulf Coast

Invest 95L Satellite Imagery, Image: NOAA

National Weather Service link tracking Gulf Low. (Click on the Gulf Low tab above the radar imagery.)

Meteorologists across the Gulf Coast are closely watching Invest 95L despite its lack of organization and poor chance of development. With oil still gushing from the bottom of the Gulf of Mexico, this low and its associated wind and wave action could drive more oil into sensitive marshes and estuaries along the northern Gulf Coast. Yesterday, hurricane specialists Lixion Avila and Chris Landsea identified the low and gave it a 10% chance of development. We’d already had our eye on it in the FOX 8 Weather Department. Today, Avila and Landsea give it a 20% chance.

Stalled Frontal Boundary, Image: Unisys

In early June and July, the main source of tropical development in the Gulf of Mexico is a low that forms off of a stalled frontal boundary in the gulf.  You can see the position of the low is about 150 miles or so south-southeast of the boot of Louisiana. There’s a lot of wind shear and dry air affecting the low right now keeping it from developing into anything tropical. Wind shear is expected to remain fairly strong over the next couple of days. So, for this thing to develop, wind shear has to relax and the dry air will have to be replaced by a warm and tropical air mass.

Water Vapor Imagery, Image: NOAA

More troubling for Gulf Coast residents is the wind and wave action associated with a low pressure system east of Louisiana. With oil gushing offshore, a persistent southeast wind could drive the oil onshore. Wave heights are currently about 5 feet around the location of the Deepwater Horizon Incident. Wave heights are forecast to become 6′ offshore, keeping skimmers and other cleanup craft in safe harbor.

-Dawn Brown

Alex and the Oil Spill

Tropical Storm Alex forms off the coast of the Yucatan Peninsula in the warm waters of the Caribbean Sea.

Infrared Satellite, TS Alex, Image: NOAA

The current track takes Alex toward the Yucatan, weakening as it crosses the peninsula. Hurricane forecasters expect it to strengthen once again in the southwestern Gulf of Mexico, moving toward the south Texas coastline before possibly curving toward the west-southwest.

Official Forecast Track, Tropical Storm Alex

Most of the computer models agree on this forecast track. Hurricane specialists from the National Hurricane Center presented their post-season analysis of the 2009 Atlantic Hurricane Season at a meteorological conference in Miami this week. During their presentation, they announced the European Model, or the ECMWF, has delivered the most successful track forecast the past few years. That model takes Alex toward the southwestern Gulf of Mexico toward central Mexico. The ECMWF isn’t plotted on most computer model tracking maps, if you follow those.

You can find the link to the European model in my link to tracking hurricanes, but it’s hard to read for most people. Keep in mind that the hurricane specialists know which models are giving the best performance when they issue their track forecast, so you can be confident that when you are looking at the 5-day forecast from the National Hurricane Center, that is the most accurate information available.

This past week, two of the government models, the HWRF and the GFDL, were taking the disturbance in the Caribbean to the northern Gulf of Mexico. You can’t really follow computer models for tropical disturbances until there is a tropical depression, or a center of circulation. It’s hard to explain, but the mathematical models are set up to take a storm that has already formed and track it. They do a pretty good job of that. But, until a low, or depression has formed, you can’t rely on all those “spaghetti plots”, as they are familiarly called.

I walked up to Bill Read, the Director of the National Hurricane Center, and I said, “Hi, Mr. Read, I’m Dawn Brown from FOX 8 New Orleans. What’s up with the  HWRF?”

Well, he smiled and said, “We initialized the model with a fake storm…, ” to try and give people battling the oil spill an idea of where Alex might go if it formed. Basically, the hurricane specialists had to input some numbers into the storm, such as maximum winds, etc., to run the model, because once again, these models are not designed to work unless there is a storm.

This is why last week, when most of the models were taking the tropical disturbance toward the west, the HWRF and GFDL were headed straight north. Now those two models are more in line with the other computer models and the official track from the National Hurricane Center reflects that.

Does that mean workers near the oil spill need not worry? No. We still have to watch Alex cross the Yucatan and see how it fares in the southwestern Gulf in the beginning of next week.

By the way, I really like Bill Read. Straight shooter, very smart, great communicator.

-Dawn Brown