Chances Increasing That the Gulf System Will Become Tropical Storm Bertha

Proving the rule that there is so much energy in the Gulf water that almost anything that spins can organize into at least a tropical depression, the expansive low-pressure system centered over the Gulf just west of Tampa Bay is getting organized. Rain bands have taken shape, and the pressure near the center of the system is slowly dropping.

In order to run specialty computer forecast models and have the computers do deeper analysis, the National Hurricane Center has designated the system Invest #91L. "Invest" meaning it's being investigated. They now put the odds in the high category that the system will organize into a tropical depression or Tropical Storm Bertha in the next day or so.

Later today, the NHC will likely switch the designation to Potential Tropical Cyclone Two. This allows them to issue Tropical Storm Watches to put boaters and coastal residents on alert. In addition, we will get a forecast cone if forecasters think there is a sufficient threat to issue the watches.

Dry air is still penetrating the circulation both from the north and the south, but moisture from the very warm Gulf should allow the system to overcome that limitation enough to organize.

Slightly hostile upper-level winds from the northeast or north are forecast to plague the system during its time over the Gulf, which should put an upper limit on its intensity. The winds will also hold most of the heaviest rain offshore, though tropical downpours will certainly affect the coastal zones from the west coast of Florida to Louisiana, including sections within about 50 miles of the coast.

There is a high consensus in the computer forecast models that the center of the broad circulation will move into the northeastern Gulf well south of Tallahassee tomorrow. After that, the future track seems to depend on how organized the system is. If it has tall thunderstorms, which seems likely, it will be pushed west in the general direction of the Louisiana coast. If it's weaker, it's more likely to continue to drift inland, but fewer computer forecasts indicate that scenario.

Here you see the location of the center as forecast by the European model (ECMWF), the U.S. GFS, the Google AI model, and the European AI model (AIFS) tomorrow and Wednesday. Notice that the dark green, where the tropical moisture is concentrated, is mostly offshore. This is the work of the upper-level winds blowing out of the north, pushing the moisture south.

Still, the biggest threat is heavy rain from a slow-moving system first over the west coast and peninsula of Florida, and then across the eastern half of the Gulf Coast and surrounding areas. Here is the map showing the forecast rain based on current forecasts. But higher amounts are likely to fall where a rotating band traverses the same area for an extended period of time.

Because of the somewhat hostile upper winds and dry air, there's no indication that, from a wind standpoint, it will get very strong. But whenever systems are drifting over the warm water of the Gulf, we pay attention, of course. In the affected areas, plan to stay aware at least until the middle of next week.