By AccuWeather senior meteorologist
Published Aug. 13, 2021 12:53 PM EDT | Updated Aug. 14, 2021 8:59 AM EDT
Florida Gov. Ron DeSantis issued a state of emergency for 23 counties on Friday as Tropical Depression Fred began closing in on the Sunshine State. AccuWeather meteorologists say that even though the system was disorganized, it still has a chance at restrengthening into a strong tropical storm as it moves through the eastern Gulf of Mexico this weekend.
Tropical storm warnings are in effect across the Florida Keys west of the Seven Mile Bridge to the Dry Tortugas. Meanwhile, Floridians in Miami, Key West, Tampa and elsewhere in the Sunshine State braced for their second brush with a tropical storm so far this hurricane season. Tropical Depression Fred was spinning about 130 miles south-southeast of Key West and moving west at 12 mph early on Saturday morning.
AccuWeather forecasters have rated Fred a 1 on the AccuWeather RealImpact™ Scale for Hurricanes in the United States. Damaging winds, isolated tornadoes and minor coastal flooding are all likely to result from Fred, but AccuWeather forecasters are most concerned by the threat of excessive rainfall and localized flooding that could unfold over the Florida Peninsula, as well as the southeastern United States mainland.
Impacts along the path of Fred in the United States are anticipated to vary dramatically. The majority of people in the storm's path are likely to have just the inconvenience of outdoor plans and travel being altered, a part of the population could experience potentially dangerous, damaging and life-threatening conditions.
That will occur as atmospheric conditions and warm waters of the Gulf of Mexico are expected to allow Fred to become a strong tropical storm over the weekend. Tropical-storm-force winds begin at 39 mph and go up to 73 mph.
Water temperatures over the eastern Gulf of Mexico are in the upper 80s F, which will favor the strengthening of Fred. When water temperatures are in the upper 70s or higher, it is considered to be favorable for tropical development and intensification.
On the other hand, persistent winds from southwest in the middle and upper levels of the atmosphere are likely to keep Fred's rainfall and thunderstorms east of its center. The disruptive winds could also limit how much the system is able to strengthen while it spins over the Gulf of Mexico.
"Because of this wind shear, the heaviest rain and strongest thunderstorms are forecast to occur first to the east of the center of circulation and later to the north and northeast of the storm center," AccuWeather Hurricane Expert Dan Kottlowski said.
Even though the center of the storm may stay off the west coast of the Florida Peninsula, torrential downpours and severe thunderstorms are likely to progress northward over the state during the weekend about a day or more in advance of the storm's arrival over the Florida Panhandle and the southeastern U.S. mainland.
The only chance for Fred to intensify into hurricane strength, with maximum sustained winds of 74 mph or higher, on Sunday or early Monday would come about if wind shear were to diminish quickly enough to allow thunderstorms to wrap around Fred's center.
The Florida Keys and the southeastern part of the peninsula are the first parts of the United States that are likely to feel the effects of Fred early Saturday morning in the form of locally drenching downpours and gusty thunderstorms.
Along with the likelihood of flooding in urban and low-lying areas as well as gusty winds that can lead to sporadic power outages, there is the potential for isolated tornadoes and waterspouts to touch down. Isolated, dangerous and damaging tornadoes can spin up anywhere over the Keys or across Florida this weekend. The risk will expand later Sunday to Monday to include the eastern part of the panhandle as well as southern Georgia.
AccuWeather forecasters are urging people in the Florida Keys and the Florida Peninsula, including beach and boating enthusiasts, to keep a lookout for rapidly changing weather conditions and to heed all warnings from officials. Seas and surf will build ahead of Fred, and squalls capable of capsizing small vessels can develop with little notice. Rip currents will increase in number and intensity from south to north this weekend along the entire Florida coastline.
"Sustained winds of 20-40 mph with gusts of 40-60 mph are anticipated over the Florida Keys and at least for the western half of the peninsula this weekend. But, as Fred gains strength over the northeastern Gulf of Mexico, the eastern part of the Florida Panhandle is likely to have a potential AccuWeather Local StormMax™ of 70 mph," AccuWeather Senior Meteorologist Adam Douty said. For comparison, hurricane-force winds are 74 mph or greater, although they must be sustained winds rather than gusts.
The amount of rain that falls over the Florida Peninsula this weekend will vary significantly and is highly dependent on the effect of wind shear in the atmosphere and bands of thunderstorms that are likely to develop due to Fred's strengthening circulation and moisture supply.
"A general 2-4 inches of rain is forecast to fall over southern and central Florida with heavier rains on the order of 4-8 inches likely with locally higher amounts over the Keys and along the Gulf coast of the Peninsula into Monday," Douty said.
Fred is forecast to make landfall over the U.S. mainland, most likely over the central part of the Florida Panhandle on Monday.
"Near, north and just east of where the center makes landfall a general 4-8 inches of rain is forecast with local amounts of 8-12 inches of rain with an AccuWeather Local StormMax™ of 12 inches possible," Douty added.
From Sunday night to Wednesday, Fred is forecast to transition from a tropical storm to a tropical rainstorm while taking a curved path inland over the southeastern U.S. During this transition, a general rainfall of 4-8 inches is most likely over western and northern Georgia, upstate South Carolina, eastern Tennessee, western North Carolina and southwestern Virginia.
Fears from early this past week of Fred potentially stalling, similar to what Florence or Harvey have done in the past, seem much less likely at this point, AccuWeather forecasters say. Florence stalled over the Carolinas in 2018, while Harvey stalled over Texas in 2017. Both systems unloaded feet of rain which triggered catastrophic flooding.
Steering breezes should remain strong enough to keep Fred moving along at a steady pace, which should substantially lower the risk of 2 feet or more of rain pouring down. Still, local rainfall amounts of 12 inches to perhaps 15 inches can occur from the eastern part of the Florida Panhandle to parts of the southern Appalachians and the eastern foothills.
Sometime on Wednesday or Thursday, Fred may dissipate over the central Appalachians or lower mid-Atlantic coast.
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Well behind Fred, Tropical Depression Seven formed over the central Atlantic on Friday before eventually strengthening to Tropical Storm Grace on Saturday morning. This storm is forecast to impact several of the same islands of the Caribbean that were just hit by Fred a few days ago.
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