An area of unsettled weather in the southern Gulf of Mexico has been churning and festering for a week now, and computer models have continued to show a tropical or subtropical system emerging from the region. Today, though still disorganized, it appears slightly more impressive in satellite images than it has in recent days, and could be heading for Florida later this week.

It’s not out of the question it brings an enhanced period of rain to the Mid-Atlantic, including the D.C. area late Friday into Saturday.

Currently, the ocean under the system is warm enough to sustain a tropical cyclone. But the upper-level winds are too strong, and the heavy thunderstorm activity is all displaced well to the east of the surface circulation, limiting its ability to intensify.


Afternoon visible satellite image over the Yucatan peninsula and southern Gulf of Mexico. (NASA)

Models are still indicating that this disturbance will develop further, and head generally northeast toward northern Florida. It should make “landfall” on Thursday night into Friday morning. I put landfall in quotes because it may be a broad disorganized system that will not look like the classic symmetric tropical cyclone.

Heavy rain and thunderstorms are already affecting the southern Florida peninsula today, and will gradually increase in coverage northward throughout the week.

While it is very unlikely that it will become anything more than a tropical depression or low-grade (sub)tropical storm, even weak storms are capable of producing extremely heavy rain which inevitably leads to flooding issues.

The latest seven day precipitation forecast from the Weather Prediction Center shows a bullseye of 7 inches expected near Fort Myers, but substantial amounts of 2 inches or more cover almost all of Florida, then up into eastern Georgia, South Carolina, and North Carolina. Locally, totals could be even greater.

Seven-day rainfall forecast. (WPC)
Seven-day rainfall forecast. (WPC)

An aircraft reconnaissance mission will fly into the disturbance later today to survey its structure and environment. If it continues the trend of getting better organized, the surface pressure will fall, the wind speed will increase, and the next phases in its lifecycle would be Tropical Depression 1, then if the sustained winds increase to 40mph, tropical storm Andrea (or subtropical storm depending on the structure). If it remains disorganized, it will still be a rain maker, but with much weaker winds.

On average, the formation date of the first named storm is July 9, but it can certainly be much earlier. Last year, Alberto and Beryl had already formed and dissipated by this date.

* Brian McNoldy is a senior researcher at the University of Miami’s Rosenstiel School of Marine and Atmospheric Science.