Gulf ‘blob’ strengthens and could become tropical storm. What does it mean for Miami?

On the first day of the 2023 hurricane season, the National Hurricane Center said in its 2 p.m. Thursday report that a trough growing in the Gulf is poised to become a tropical storm as early as Thursday afternoon.

The system began earlier this week as a disorganized area of low pressure near the northeastern Gulf of Mexico.

Here’s what the system looks like, according to the center’s observation of satellite wind data, along with buoy and ship observations.

The area of low pressure over the northeastern Gulf of Mexico has a broad but well-defined circulation with maximum sustained winds of about 35 mph. Shower and thunderstorm activity is showing signs of organization.

“Environmental conditions remain marginally favorable for additional development, and if these trends continue, a short-lived tropical depression or storm is likely to form as soon as this afternoon,” forecasters Philippe Papin and John Cangialosi said in the Thursday afternoon report.

The system is likely to meander over the northeastern Gulf of Mexico through Thursday night but begin a slow southward motion on Friday. If the system — dubbed Invest91L by the hurricane center and “Gulf of Mexico blob” by some storm watchers — becomes a tropical depression or storm, that would likely be its high point. By Saturday and Sunday, environmental conditions are forecast to become unfavorable for additional development as the system continues moving southward, likely remaining offshore over the Gulf of Mexico.

Formation chances have increased from 50% to 70% through both 48 hours and seven days, considered “high,” by the hurricane center.

An Air Force Reserve Hurricane Hunter aircraft is scheduled to investigate the system Thursday afternoon.

What the trough will do to local weather

Tropical system or not, heavy rainfall could pelt the Florida Peninsula through this weekend, a point also noted by the National Weather Service in Miami.

A weather statement was issued Thursday afternoon through 2:45 p.m. for parts of Hialeah, Miami Gardens, Miami Lakes, Doral, North Miami, Miami Shores and Miramar for strong thunderstorms, with winds approaching 40 mph.

South Florida faces two to four inches of heavy rain and flooding that could top six inches Thursday, Friday and Saturday.

A flood watch issued Wednesday remains in effect and is extended into Saturday because of expected rounds of rain.

Affected areas include:

Coastal Miami-Dade, Broward and Palm Beach counties.

Far South Miami-Dade.

Inland Miami-Dade, Broward and Palm Beach counties.

Metro Miami-Dade, Broward and Palm Beach counties.

Glades and Hendry counties.

Wettest hours

Miami-Dade and Broward 48-hour hourly outlook concerning rain, according to the weather service.

5 p.m. Thursday: 63%.

8 p.m. Thursday: 43%.

11 p.m. Thursday: 20%.

2 a.m.-5 a.m. Friday: 10%.

8 a.m Friday: 29%.

11 a.m. Friday: 42%.

2 p.m. Friday: 67%.

8 a.m.- 11 a.m. Saturday: 61%.