How Helene’s tropical moisture could cause significant flooding in Atlanta and the Southeast before landfall
The impacts of Helene will be widespread, as Helene will bring moisture throughout the Southeast and cause flash flooding in the region. September 24, 2024.
ATLANTICA — On the eve of Tropical Storm Helene, much of the Southeast, including the Atlanta metropolitan area, is at risk of dangerous flash flooding on Wednesday, even though Helene will be hundreds of miles away.
The expected torrential rains are due to a combination of factors: Tropical moisture moving in ahead of Helene’s expected arrival on Thursday is interacting with a slowing front and the terrain of the Appalachian Mountains, creating a recipe for persistent rain.
That pattern alone is conducive to flash flooding. But once the storms reach northern Georgia, western Carolina and far eastern Tennessee, they will struggle with the terrain of the southern Appalachians, according to the FOX Forecast Center.
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The mountains help transport moisture upwards, forcing out even more rain and potentially causing flash floods.
“(Helene will) bring all this moisture, not just from the Gulf (of Mexico). Some of it will come from the western Atlantic,” said Steve Bender, meteorologist at FOX Weather. “We know it’s that warm current, that Gulf Stream – all of that is going to be thrown into the mountains. That’s going to cause a big rain event.”
Farther south, the zone of persistent flooding appears to remain in or near the Atlanta area, and increased runoff from urban areas will also increase the risk of flash flooding, particularly when it comes to roads and small streams and rivers, the FOX Forecast Center said.
NOAA’s Weather Prediction Center rated the region at a Level 3 of 4 flood risk on Wednesday because total rainfall from the event could reach or exceed 4 inches (10 cm).
(FOX Weather)
This lays the foundation for the ground to be saturated with flooding when Helene arrives on Thursday and brings direct tropical downpours.
By the time Helene moves out on Friday, some areas of Georgia, especially in the northeast, could see more than 8 inches of rain. Western regions of North Carolina and eastern Tennessee could see up to 10 inches or more by Friday.
The potential for several inches of rain so close to the arrival of rainfall associated with a major hurricane will greatly exacerbate the impacts of flooding resulting from Helene’s rains, the FOX Forecast Center said.
