If you want to understand why Harvey is lingering for days and days over the Gulf Coast and dumping catastrophic rain, look to the winds.
Ordinarily such tropical storms are steered by mid-to-upper level wind systems, but in this case, Harvey became positioned in a band between the westerlies to its north and trade winds to its south, meaning there was no force to shepherd it elsewhere, said Tim Morrin, National Weather Service meteorologist in Upton.
Harvey is not the first tropical system to get stranded in the Gulf Coast area due to lack of steering winds.
“Residents of this same region may remember Tropical Storm Allison,” which in June of 2001 “made an initial landfall and then meandered for days,” wrote Marshall Shepherd, director of the atmospheric sciences program at the University of Georgia, in a Forbes.com article, adding that the storm produced “nearly 3 feet of rainfall and caused life-altering flooding.”
A lack of wind power was also blamed for that storm’s languishing.
“On average, the steering currents over Southeast Texas during the tropical season are much weaker than for more northern latitudes,” according to the weather service’s Houston/Galveston’s office.
Still, just as Allison ultimately moved on, Harvey is forecast to do so, too.
Now a tropical storm, Harvey is expected to make landfall again Wednesday morning near the Texas/Louisiana border, then track to the northeast, according to the National Hurricane Center.
“Harvey has been steered north-northeastward by a light southwesterly flow between a high in the Gulf of Mexico and a trough over the central United States,” the hurricane center said in its 4 p.m. CDT Tuesday update. “This flow pattern should keep Harvey on the same general track and speed with a gradual turn to the northeast in about 3 days.”
That means up through Louisiana, Mississippi and into Tennessee.
As for Long Island, there is “nothing worth worrying about, as the storm will lose most of its moisture during its slow trek northeast,” said Bill Korbel, News 12 Long Island meteorologist, who expects “no effects here other than some rain showers Saturday night into Sunday.”