AccuWeather forecasters up risk for tropical development near Southeast
The GOES-16 visible satellite shows a tropical concern off the Southeast coast July 23, 2021. Lightning activity is shown in the color overlay. (NOAA/CIRA)
AccuWeather meteorologists warn that a broad area of disturbed weather that was slowly spinning over the warm waters of the Gulf Stream just east of Florida and north of the Bahamas on Saturday has the potential to gradually develop into a tropical depression or storm over the next few days.
Showers and thunderstorms associated with the feature, which the National Hurricane Center (NHC) dubbed Invest 90L on Friday, ignited just off the coast of Georgia and northeastern Florida from Wednesday to Thursday. AccuWeather forecasters, who have been tracking the possibility for development in this area all week, upped the potential for tropical development off the Southeast coast to medium on Friday morning as the thunderstorms grew more vigorous.
As of Saturday morning, the mass of squalls over the waters off Florida and the northern part of the Bahamas was showing signs of some spin or a developing circulation.
"While waters are plenty warm enough to support a tropical system east of Florida, wind shear is significant, and an injection of dry air from the north may tend to limit development in the short term," AccuWeather Senior Meteorologist Rob Miller said.
Generally, water temperatures of 79 degrees Fahrenheit or greater are needed to allow tropical development. Sea surface temperatures in the vicinity of the disturbance ranged from 82 to 84 degrees.
Wind shear is the change in direction and strength of breezes at progressively higher layers of the atmosphere as well as horizontally just above the sea surface. When there are abrupt changes with these breezes, it can hinder tropical development and sometimes cause an organized tropical system to weaken or change course.
There was a significant amount of wind shear in that area east of Florida on Friday, and dry air was streaming in from the north.
"Both of these factors tend to work against rapid tropical development and will be factors that may hold this system back," Miller explained.
If it does overcome the hurdles and become a tropical storm, it will be given the next name on the list of tropical storms for the 2021 Atlantic hurricane season, which is Fred. The name Fred has never been used to name a tropical storm in the Atlantic. That's because the previous "F" storm, Florence, a hurricane, was retired after devastating the North Carolina coast in 2018 with high winds and extensive flooding.
The system is forecast to spin slowly toward the southwest through the end of the weekend.
There have been five named systems thus far in 2021 over the Atlantic basin. Claudette, Danny and Elsa made landfall in or affected the southeastern United States as tropical storms. Elsa reached Category 1 hurricane status while over the eastern Caribbean and again just west of Florida and is the only storm that reached hurricane force so far this year.
AccuWeather meteorologists are projecting 16-20 named tropical systems in the Atlantic for 2021 with additional landfalls in the U.S. foreseen.
Following the usual lull in tropical activity during the middle of the summer, an uptick in named systems is anticipated toward the end of the summer and into autumn. However, to have five named systems by early July, as was the case with Elsa, is highly unusual.
The average formation date for the fifth named tropical system in the Atlantic is not until the end of August. During the record-breaking 2020 Atlantic hurricane season with its 30 named systems, there were eight named storms as of July 23. For a time into early July, the 2021 season was keeping pace, but it has since fallen behind last year's record track.
Anticipated impacts to Florida, northern Bahamas this weekend
While a push of dry air may tend to keep showers and thunderstorms away from the southeastern areas of the Carolinas and Georgia, as well as northeastern Florida, storms are likely to ramp up in frequency and intensity over the southern half of the Florida Peninsula and the northern part of the Bahamas.
The majority of the storms packing torrential downpours, gusty winds and frequent lightning strikes would tend to occur primarily south of the popular theme parks in central Florida, although a rogue storm cannot be totally ruled out.
People heading to the Atlantic beaches should keep an eye out for rapidly changing weather conditions, sudden thunderstorms and a lightning strike risk. Since the system is spinning offshore with its gusty thunderstorms, an uptick in the number and strength of rip currents is likely along the Atlantic coast of Florida as well as the Georgia and Carolina beaches.
Systems such as this have the potential to produce waterspouts. Pleasure boaters and anyone out on fishing trips in the area should keep an eye out for these potentially dangerous storms.
"As the center of the system spins southwestward, it could cross the southern part of the Florida Peninsula late this weekend to early this upcoming week," AccuWeather Senior Meteorologist Bob Smerbeck said.
"If this track materializes, regardless of the system's organization, there may be the risk of isolated tornadoes over South Florida from Sunday to Monday," Smerbeck explained.
If the feature fails to develop through this weekend, it is possible the broad area of disturbed weather splits into two main parts.
"This split could create not only one area to watch this week, but also two features," AccuWeather Senior Meteorologist Paul Walker stated.
One area of concern would be roughly the same general area, off the southern Atlantic coast of the U.S. and the other could end up in the Gulf of Mexico.
Elsewhere in the Atlantic, there were no areas showing potential for tropical development through this weekend and into early week.
The combination of strong wind shear and dry, dusty air is forecast to inhibit tropical development from the Caribbean to the northwestern shores of Africa.
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