JeffMasters, 4:15 PM EDT on August 26, 2008
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The track forecast for Gustav
The latest 12Z (8 am EDT) model runs continue to be in good agreement on the 1-3 day track of Gustav, and we can be confident that Gustav will turn west and pass south of Cuba after leaving Haiti. The trough of low pressure currently exiting the U.S. East Coast and pulling Gustav northwest is expected to move off to the east, allowing a ridge of high pressure to build in and force Gustav due west or slightly south of due west. After three days, there is more divergence in the models. The NOGAPS model no longer foresees landfall on Mexico's Yucatan, and now takes Gustav to a final landfall in the Florida Panhandle on Monday. The ECMWF is now the only model predicting a landfall in the Yucatan. This model predicts a second landfall in Texas. The GFDL is a little slower than its previous run, but still forecasts a Category 3/4 hurricane hitting Louisiana on Sunday evening. The UKMET prefers a Texas landfall. The GFS is not much help--it dissipates Gustav.
The final landfall location of Gustav depends on the strength and speed of a trough of low pressure forecast to move across the Midwest U.S. late this week. At present, there is no way to guess which location in the Gulf of Mexico is the most likely.
Keep in mind that the cone of uncertainty is correct only about 2/3 of the time--1/3 of the time, we can expect the storm's position to be in error by more than what the cone of uncertainty suggests....
Gustav's intensification potential in the Gulf of Mexico
As we saw in 2005 with Katrina and Rita, the large amounts of deep, warm water brought into the Gulf of Mexico by the Loop Current can help intensify hurricanes to Category 5 intensity. As explained in my
Loop Current tutorial, the Loop Current is an ocean current that transports warm Caribbean water through the Yucatan Channel between Cuba and Mexico. The current flows northward into the Gulf of Mexico, then loops southeastward through the Florida Keys. The Loop Current commonly bulges out in the northern Gulf of Mexico and sometimes will shed a clockwise rotating ring of warm water that separates from the main current. This ring of warm water slowly drifts west-southwestward towards Texas or Mexico at about 3-5 km per day. This feature is called a "Loop Current Ring", "Loop Current Eddy", or "Warm Core Ring", and can provide a key source of energy to fuel rapid intensification of hurricanes that cross the Gulf. The Loop Current itself can also fuel rapid intensification, such as happened with Hurricane Charley in 2004. When a Loop Current Eddy breaks off in the Gulf of Mexico at the height of hurricane season, it can lead to a dangerous situation where a vast reservoir of energy is available to any hurricane that might cross over. This occurred in 2005, when a Loop Current Eddy separated in July, just before Hurricane Katrina passed over and "bombed" into a Category 5 hurricane. The eddy remained in the Gulf and slowly drifted westward during September. Hurricane Rita passed over the same Loop Current Eddy three weeks after Katrina, and also explosively deepened to a Category 5 storm....
Elsewhere in the tropics
Most of the computer models forecast the development of two more tropical waves between Africa and the Lesser Antilles Islands in the coming week, and it is possible we will have three or four simultaneous named storms in the Atlantic a week from now (Figure 3).
If Gustav brings as much craziness as Fay, I might move to the military school for a while--it's supposedly the highest spot in town.
