Tropical Moisture to Douse Deep South Early This Week

By Brett Rathbun, AccuWeather.com Meteorologist

September 28,2015; 11:10PM,EDT

 

 

Regardless of whether or not a tropical system develops over the Gulf of Mexico, heavy rain will be unleashed across the Deep South to end September.
The system responsible for the heavy rainfall will track northward toward the central Gulf Coast early this week.
This system being monitored is identified as 99L, according to the National Hurricane Center.
Satellite Loop Over the Gulf of Mexico (Image/NOAA).
The environment over the Gulf of Mexico is somewhat conducive for tropical development.
According to AccuWeather Meteorologist Evan Duffey, "Water temperatures over the Gulf are very warm, which should allow for development; however, wind shear is strong over the Gulf which would inhibit development."

According to AccuWeather Senior Meteorologist Alex Sosnowski, "Wind shear is the changing of wind direction and speed at various levels of the atmosphere. In order for tropical systems to form or strengthen, wind shear must be weak."
"While convection should flourish, it will likely be pushed well east of the center of circulation, which would prevent any development," Duffey said.
In order for a system to become a tropical cyclone, a low-level circulation must be present with organized convection surrounding the center. Should convection be sheared on only one side or disorganized, it is unlikely to develop.

Unsettled Weather across the Gulf of Mexico

While the chance for development would remain very low over the southern Gulf, conditions could be more favorable over the northern Gulf.
"Shear is slightly more relaxed over the northern Gulf," Duffey said. "While the shear may still be too much for the low to overcome, there is still a slight change it could gain tropical status prior to moving over the U.S."
Duffey mentioned that if it were to develop, it would likely intensify to only a tropical depression.
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This system nonetheless contains abundant moisture which could lead to flash flooding in the hardest hit areas along the Deep South.
Heavy rain fell across portions of the Gulf Coast on Sunday. Mobile, Alabama, and Pascagoula, Mississippi, received over 7 inches of rainfall.
"Gusty winds, building seas, rough surf, minor coastal flooding and severe thunderstorms may become concerns for petroleum and coastal interests," Sosnowski said.
Rain will continue across much of the Deep South into midweek.

According to AccuWeather Meteorologist Michael Doll, "A few organized clusters of thunderstorms will likely produce rainfall amounts over 3 inches and can cause flooding."
"In the absence of flooding rain, downpours would not be a terrible thing for portions of the upper Gulf Coast," Sosnowski said. "Places from the Florida Panhandle to Louisiana are experiencing abnormally dry to severe drought conditions."
Rain will soak areas including Galveston and Port Arthur, Texas; New Orleans and Slidell, Louisiana; Gulfport and Biloxi, Mississippi; Mobile, Alabama; and Pensacola, Panama City and Tampa, Florida.
The greatest threat for flooding will focus from southern Louisiana to western Florida.
Those traveling along Interstate 10 from Florida into Texas could deal with wet morning and afternoon commutes to and from work.
Track rain across your area this week using AccuWeather Minutecast®.

Those along the Gulf coast should monitor this system over the next couple of days.
While AccuWeather will continue to provide updates on this system, other features are being monitored across the Atlantic Basin.
A feature located between the Bahamas and Bermuda became Tropical Depression 11 on Sunday night.
"This feature will likely never become strong enough to become a tropical storm," Duffey said. "Therefore, it will likely live out its life without being given a name."
Tropical Depression 11 will spread heavy showers and thunderstorms over Bermuda during the first part of the week.
"During the latter part of the week and into the weekend, Tropical Depression 11 has the potential to join up with a front along the Atlantic coast and add to the anticipated drenching rain," Sosnowski said.
Ida dissipated to a remnant low over the open waters of the Atlantic on Sunday.
"Because of the persistent wind shear, the chance of a major hurricane impacting the United States for the remainder of 2015 is very low," AccuWeather Hurricane Expert Dan Kottlowski said. "Research from the Colorado State University shows that since 1878, no major hurricanes have impacted the U.S. in October and November during El Niño years."