Vast Storm Battling Lots Of Dry Air And Tug Of War Between Multiple Vortices

On Tuesday afternoon after much anticipation, Tropical Depression Nine in the Western Atlantic was found by Air Force Reconnaissance aircraft to be strong enough and well organized enough to become the ninth named storm of the 2012 Atlantic Hurricane Season. Since then, things have been a struggle for Tropical Storm Isaac.

The storm, which has grown to be about the size of Texas, remains in rough shape on this late Thursday morning. Dry air to the north, west, and south of the storm has been one factor that has made it very difficult for the storm to strength. Another issue is the circulation itself, or should we say multiple circulations. As pointed out on the evening broadcasts from The Weather Channel, Isaac has had to deal with several competing vortices that are all battling to take over the storm.

One appeared further to the south and west of the actual center while another was to the north of the storm. Thunderstorms have struggled to wrap around the circulation. To sum it all up, Isaac was literally one big mess. Since then, Isaac has reformed further south. A consequence of that appears to be a more westward track, but that will not keep it from interacting with the mountainous terrain of some of the bigger islands such as Hispaniola, which has mountains as high as 10,000 feet, and Cuba, which has mountains as high as 6,000 feet.

Moving more westward, Isaac will also be more over water and become a threat for the Central Gulf Coast states of Alabama, Mississippi, and Louisiana. Still a lot of time to watch it though, but last night, the European Model did indicate that the storm would take a more westward track into the Gulf by early next week. The GFS had indicated more of a track toward the west coast of Florida, where the Republican National Convention is scheduled to take place in Tampa. Orange futures were up five percent on Wednesday in response to the possible threat from Isaac.

As of the 11:00 AM EDT Advisory on Thursday from the National Hurricane Center, Isaac had weakened to minimal tropical storm force with maximum sustained winds of 40 miles per hour, gusts of up to 50 miles per hour, and a minimum central pressure of 1003 millibars, or 29.62 inches of Hg. Tropical storm force winds extend some 140 miles from the center. Isaac had basically remained at the same intensity all day on Wednesday with maximum sustained winds of 45 miles per hour, and a minimum central pressure of 1003 or 1004 millibars before weakening slightly overnight and this morning.

There did appear to be some signs that Isaac was going to get its act together on Wednesday night. Convection to the north of the center looked like it was trying to wrap around the center, which is an indication of intensification. However, Issac’s center reformed further south and the storm lost some strength overnight. The latest forecast discussion indicates that while the satellite imagery indicates some improvement with the system, Air Force reconnaissance still finds the system very disorganized. The intensity forecast calls for gradual intensification with Isaac becoming a hurricane within 36 hours. Sea surface temperatures and upper level winds are just right for rapid deepening, but as long as the storm’s core struggles to get organized, it will not be able to take advantage of the environment.

After Isaac becomes a hurricane, it will start interacting with land and weaken by 72 hours before moving out over water again and strengthen by 96 to 120 hours. The forecast also indicates that despite the reformation to the south, and a more westward track, Isaac could still be a problem for Florida.