Tropical threat diminishing, but flooding risk remains for Southeast
The chances of flooding in your community can change over time. Some people live or work in properties at risk of flooding and may not even know it.
Rounds of showers and thunderstorms with the risk of localized flooding will continue over the southeastern United States through the end of the week and into the weekend due largely to a deadlocked weather pattern.
AccuWeather meteorologists said concerns for a tropical depression to spin up over the northern Gulf of Mexico have diminished due to persistent wind shear, despite water temperatures close to 90 F, or about 12 degrees above the minimum threshold for tropical development.
However, problems from the downpours will persist, even though the potential for a tropical system to develop has waned considerably.
In this image captured on Thursday, July 14, 2022, there was no sign of circulation or organization of clouds over the Gulf of Mexico (left). A large and loose swirl of clouds near the Bahamas (center) was associated with a non-tropical storm. (GOES-East/NOAA)
Wind shear is a stiff straight-line breeze at various levels of the atmosphere. This breeze can blow from one direction or different directions and is often a deterrent for tropical development over much of the Atlantic basin during the middle of the summer.
Without an ongoing organized area of low pressure, AccuWeather meteorologists dropped the designation of tropical rainstorm on Wednesday. Weak tropical low pressure areas, without reaching the official criteria for a tropical depression or storm, have unleashed flooding rainfall in the past. Alex, as a tropical rainstorm, was a recent example of an organized system that produced flooding downpours prior to becoming a tropical depression and storm as it crossed the Florida Peninsula in early June.
However, the potential for flash flooding will continue as an old frontal zone and southward dip in the jet stream will remain the key players in the unsettled, murky and humid forecast.
The front represents a boundary between very humid and slightly less humid air, and showers and thunderstorms tend to fire near this dividing line. Meanwhile, the southward dip in the jet stream represents a pocket of cool air over the middle and upper part of the atmosphere. This setup allows clouds to tower high above the ground and unleash tremendous amounts of rain.
"In a pattern such as this, it is impossible to say exactly which locations will be hit by torrential downpours from one day to the next, but the risk of localized flash flooding will persist through this week and into this weekend," AccuWeather Senior Meteorologist Brett Anderson said.
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Two separate flash flood events threatened lives earlier this week over the southern Appalachians. Torrential rain led to flash flooding in Buchanan County, Virginia, where dozens were still missing Thursday morning in the southwestern part of the state. Farther to the southwest, near Gatlinburg, Tennessee, flash flooding forced hundreds of evacuations.
Populated areas such as Augusta, Georgia, Houston and Fort Bragg, North Carolina, were hit with several inches of rain in less than three hours when the pattern was ramping up last Thursday. The storms have been successful in slashing daytime heat in the East, but not so in the Central states, where temperatures in Houston have topped 100 degrees for several days in a row.
Another weak front will drop southward into the region this week, and that can aggravate the already busy nature of showers and thunderstorms.
The daily rounds of showers and thunderstorms have been chipping away at abnormally dry to drought conditions in southeastern states along the Atlantic coast, but rainfall has largely avoided most areas from central Mississippi to Texas.
In much of the Southeast, downpours that have been occurring on a nearly daily basis will continue through Friday. The downpours will bring disruptions to travel and outdoor activities, including those with getaways at the beach or over the mountains, according to forecasters.
Approximate location of flash flood incidents from Monday evening, July 11 through Wednesday morning, July 13, 2022.
Motorists are urged not to attempt to drive through flooded roadways as the water may be deeper than it appears, experts say. Likewise, people spending time outdoors should seek shelter at the first rumble of thunder to reduce the risk of being struck by lightning.
About 500 miles to the southeast, over the Bahamas, a non-tropical storm in the middle layers of the atmosphere drifted westward this week. Like the system struggling in the Gulf, the chance of this feature organizing into a depression or storm is unlikely.
Energy and moisture from this Caribbean storm are likely to give yet another boost to the weather systems hanging around in the Southeast this weekend. Some of the first places to experience the boost in terms of heavy downpours and thunderstorms from this system are likely to be portions of the Florida Peninsula starting on Friday. Residents of Florida are likely well aware that most storms in the summertime can pack a punch, and there is the potential for some places in the Sunshine State to get walloped by torrential downpours and gusty winds.
"During this weekend, there are some signs that the jet stream dip will shift slightly farther to the west in the Southern states," AccuWeather Senior Meteorologist Joe Lundberg said. "That could allow more storms to fire up farther to the west, say over portions of the middle Mississippi Valley."
The same westward drift of the jet stream might lead to more sunshine and less frequent downpours along the southern Atlantic coast. But the sunshine boost, along with that Caribbean system, could allow the storms that fire to be more robust.
Despite whatever subtle shift in the jet stream occurs, the nearly daily barrage of thunderstorms is likely to continue in cities such as Atlanta, Charlotte, North Carolina, and Greenville, South Carolina. Cities such as New Orleans and Birmingham, Alabama, that have avoided many of the downpours so far may not be so lucky moving forward.
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