Gulf Coast could be in for flooding, but tropical storm is less likely

Yet another flooding event is possible, this time along the Gulf Coast on Thursday and Friday, as a tropical disturbance tracks toward Louisiana.

The chance that the disturbance will turn into a tropical storm appears slimmer than it was earlier this week. The next one that forms will be named “Dexter,” but it’s looking less likely that will happen anytime soon.

The system is now centered over land in Florida, not water. It can’t strengthen until it begins drawing energy from the warm waters of the Gulf of Mexico. That’s why it’s unlikely to become anything more than a low-end tropical storm, if that.

The main threat will be heavy rainfall. Localized flooding is possible once the system moves ashore sometime Thursday into Friday, which could happen in Louisiana. The National Weather Service’s Weather Prediction Center has already said there is a moderate (Level 3 out of 5) risk of flash flooding and excessive rainfall for Friday. It includes central and western Louisiana, but not the New Orleans metro.

“Regardless of development, the associated tropical moisture plume will support heavy rainfall rates” of 2 to 3 inches per hour, the Weather Service wrote.

As of midmorning Wednesday, it was centered in the Florida Panhandle between Apalachicola and Tallahassee. Surface winds flowing into the system were between 5 and 15 mph.

That means that the disturbance, currently dubbed Invest 93L, is weak. It’s not inhaling much air because it’s not strong, and that’s why winds flowing into it are minimal.

To get stronger winds, the system would need to move over water. The warm waters would heat air from below, causing the air to rise. Then air outside the system would spiral in to fill the void left by the rising air. That’s how tropical storms and hurricanes work.

The National Hurricane Center maintains that the disturbance has a 40 percent chance of eventual development, but noted that’s conditional on “if this system moves far enough offshore.”

Water temperatures off the shore of Alabama, Mississippi and Louisiana are around 90 degrees. The system is forecast to track over these unusually warm waters through Thursday, potentially causing it to intensify into a depression or storm before it pushes ashore in Louisiana.

Over the next 24 hours, Invest 93L will skirt along the coast and probably remain sloppily structured. As long as the center remains near or over land, minimal intensification is expected.

However, there’s a low chance that the center could drift offshore a bit Wednesday night into Thursday, tugged into the gulf by heavier thunderstorms to the south. It would then encounter water temperatures of 86 to 90 degrees near the Mississippi Delta off the coast of Louisiana. That would provide a small window for the storm to strengthen, and a tropical depression or borderline tropical storm could be possible.

Regardless, showers and thunderstorms will continue to circulate around the system. On Thursday and perhaps early Friday, a few waterspouts are possible near the coasts of Mississippi, Alabama and west of Panama City in Florida due to enhanced low-level vorticity, or spin, associated with the system.

Otherwise, a belt of moderate to locally heavy rains will be ongoing in central and western Louisiana.