This post, originally published at 12:40 p.m., was updated at 3:10 p.m.
A tropical storm in the Gulf of Mexico may dump more than 10 inches of rain over portions of the northern U.S. Gulf Coast through Friday of this week raising the specter of significant flooding in the hardest-hit areas.
The storm, which earned the name Cindy Tuesday afternoon, is one of two active storms in the tropical Atlantic Ocean basin. Forecasters are also monitoring Tropical Storm Bret in the eastern Caribbean, though it is forecast to weaken. It is the first time we have seen two simultaneous pre-July named storms in the Atlantic since 1968.
Given the gulf system’s potential to unload copious rainfall along the U.S. Gulf Coast, it is of greatest concern. Tropical storm warnings have been posted from High Island, Tex., to the mouth of the Pearl River in Louisiana.
This is an expansive system, already bringing heavy rain from the Florida panhandle to southeast Louisiana. The storm is centered about 265 miles south of Morgan City, La., or about 355 miles southeast of Galveston, Tex., and is stationary.
The system packs 45 mph winds, but its biggest hazard is expected to be its rainfall.
The latest three-day rainfall forecast from the Weather Prediction Center includes a bull’s eye of at least 10 inches over coastal Mississippi and Alabama, including Biloxi and Mobile.
Flash flood watches have been posted for much of this area through Thursday evening, and the National Weather Service is warning of “multiple rounds of very heavy rain” resulting in the potential for “significant” flash flooding.
In addition to the freshwater flooding from rainfall, a rise in water or storm surge of about one to three feet is expected along the Louisiana coast, and perhaps stretching into Mobile Bay, east of where the center of the system makes landfall. This may produce minor to moderate coastal flooding. The effect of storm-surge flooding would be maximized if it occurs during high tide.
While forecasters are most concerned about rain, tropical-storm-force wind gusts — perhaps up to 50 mph — are forecast to arrive in coastal Louisiana late Tuesday evening and to persist through Wednesday.
Forecasters are stressing that most of the system’s most significant impacts will occur a good deal east of its landfall location because of its asymmetric shape, which has resulted from wind shear.
The system’s official track forecast, represented by the “cone of uncertainty” that shows where the center has the best chance (66 percent probability) to make landfall, brings the system ashore near the Texas-Louisiana border. But that is well west of where the strongest winds, heaviest rain and greatest storm surge are expected to occur — from coastal Louisiana to the western panhandle of Florida.
Once the system moves inland, it is expected to weaken, but its remnant moisture may spill northeastward toward the Tennessee Valley on Thursday, and the Mid-Atlantic and Northeast on Friday and Saturday, perhaps leading to heavy rainfall in these areas.
Tropical Storm Bret
Tropical Storm Bret, which was named Monday afternoon near the Windward Islands, has crossed into the eastern Caribbean Sea after making landfall on Trinidad and Tobago on Monday night. Coincidentally, the last time Trinidad was hit by a named storm was by a Tropical Storm Bret in 1993. That was also the last storm to come so close to the Venezuelan coastline.
On Monday, Bret became the earliest tropical storm on record to form in the Atlantic Ocean’s “main development region,” which refers to the area of the deep tropics between Africa and the eastern Caribbean.
— Philip Klotzbach (@philklotzbach) June 19, 2017
Not only did Bret form unusually far to the east so early in hurricane season, but also unusually far to the south. Only one other pre-July system on record achieved tropical storm status at a lower latitude than Bret: the 1933 Trinidad Hurricane. Interestingly, 1933 was an incredibly active hurricane season, up in the ranks with the mega-seasons of 1893, 1926, 1995 and 2005.
Bret is forecast to continue its journey along the southern periphery of the Caribbean as a tropical storm, but it will enter the central Caribbean “hurricane graveyard” Wednesday, where many storms meet their demise because of the frequent presence of very strong vertical wind shear. The storm should dissipate by Thursday.
Bret may have been a fluke, but it may also be a harbinger of an active season for tropical waves that originate over Africa.
Jason Samenow contributed to this report.