Hurricane Humberto has become a major hurricane with 115 mph winds out in the Atlantic Ocean, and could strengthen even further, but it’s not the storm that poses the most danger to U.S. shores.
No, the storm that U.S. residents have to worry most about was dubbed Potential Tropical Cyclone Nine at 5 p.m. on Sept. 26. That storm, about 55 miles off the northeast end of Cuba, is expected to soon become Tropical Storm Imelda, the National Hurricane Center said.
The center’s initial forecast shows the storm could briefly strengthen into a hurricane as it moves northward through the Bahamas and past Florida, then weaken into a tropical storm again before making landfall somewhere between North Florida and Southeast North Carolina on Wednesday, Oct. 1.
“An increasing threat of heavy rainfall from this system is forecast over the southern Mid-Atlantic through coastal Georgia which could cause flash, urban, and river flooding into next week,” the hurricane center said in the update.
The other growing concern for millions across the Carolinas and into Virginia isn’t tropical at all. It’s the slight risk for excessive rainfall ahead of the storm in a phenomenon the National Weather Service calls a predecessor rain event. If that sounds familiar, it’s because a similar event took place in mountainous areas of North Carolina and Tennessee before Helene arrived a year ago.
A cold front sitting over the Appalachians is generating showers, and could continue to generate rain through the weekend, with the bulk of the rainfall slowly shifting eastward over the weekend, said Scott Kleebauer, a meteorologist at the Weather Prediction Center.
By Sept. 28, Kleebauer said the showers and thunderstorms in the eastern Carolinas could begin pulling in early bits of tropical moisture out in front of the approaching tropical system, expected to be Imelda by then.
To be clear, the weather service isn’t forecasting Helene-like extreme rainfall, but is urging residents, especially in southeastern North Carolina and coastal South Carolina to expect heavy rain, potentially through the end of September.
Meanwhile, although Humberto is forecast to remain out to sea, it could still affect the path of soon-to-be Imelda through a meteorological process known as the Fujiwhara effect.
How all of the weather systems moving into the larger overall region interact with one another will determine the extent of impacts the storms could have on the U.S. East Coast, the Bahamas and potentially Bermuda over the next few days. But the risks are growing for impacts along the coast between Florida and North Carolina, National Hurricane Center director Michael Brennan said on the evening of Sept. 25.
Showers and thunderstorms continue to show improved signs of organization on Sept. 26, and it’s expected to become Tropical Storm Imelda within 24 hours, according to the hurricane center. The current forecast predicts the storm will move into the central and northwestern Bahamas through the weekend.
Tropical storm watches and warnings went into effect on Friday afternoon for portions of the Bahamas, where the hurricane center forecasts 4 to 8 inches of rain.
Eastern Cuba, where the potential tropical cyclone was centered 55 miles offshore, is forecast to see 8 to 12 inches of rain, with isolated totals up to 16 inches possible, the hurricane center said. Hispaniola, Jamaica and portions of central and southern Cuba are expected to receive up to an additional 4 inches of rain. “This rainfall will likely produce flash and urban flooding, the hurricane center said. “Mudslides are also possible in areas of higher terrain across eastern Cuba, Hispaniola, and Jamaica.”
By Monday, Sept. 29, the forecast grows considerably more uncertain, according to the hurricane center. It depends in large part on Imelda’s forward speed, which could either put it into sooner proximity with the cold front moving over the Southeast, or slow it down and increase the chances of a stronger interaction with Hurricane Humberto as the two systems near each other early next week, said Brian McNoldy, a senior research associate at the Rosenstiel School of Marine, Atmospheric, and Earth Science at the University of Miami.
In Charleston, South Carolina, National Weather Service meteorologist Blair Holloway said on the morning of Sept. 26 that confidence in the forecasts for the storm “has not increased or changed much from yesterday (Sept. 25).”
“Considerable uncertainty remains including its development, track, intensity, timing, and potential impacts,” Holloway said.
“A majority of the (model) solutions, but not an overwhelming majority, bring the system toward the Carolinas by around Tuesday,” said Houston-based meteorologist Matt Lanza on his Substack “the Eyewall” on Sept. 26. “However a non-trivial number of models peel the system back to the east, into the open Atlantic, due in part to some complex interactions with Hurricane Humberto.”
“Anyone having confidence in what, precisely, will happen at this point is probably not being honest with themselves (or you),” he added.
Heavy rain might end up being the main calling card of Imelda. “There is real potential here for a rainmaker in the Carolinas, and particularly North Carolina,” Lanza said. “Readers there will certainly and understandably be concerned that this could become another Hurricane Helene-like event. For now, we think that is unlikely, as the strongest rains appear to be east of areas most impacted by Helene, and the overall signal for prolonged, heavy rainfall is lower this time.”
For now, he said, NOAA is predicting 6 to 10 inches of rainfall for areas hardest hit, which is no picnic, but also far from reaching Helene-levels.
At 5 p.m. on Sept. 26, Humberto was centered about 430 miles northeast of the northern Leewards and moving northwest at 5 mph, with sustained winds of 115 mph.
For now, Humberto is forecast to follow a pattern similar to Erin, moving between the U.S. and Bermuda, but the strengthening Humberto is increasing the risks of long period swells that could make seas and surf hazardous along the U.S. coast, the hurricane center said. Humberto’s exact track is uncertain and remains tied to the future of the potential Imelda and other weather systems in the region.
Humberto is forecast to ultimately reach wind speeds of 150 mph, about 1,100 miles east-southeast of Miami by Sept. 28, the hurricane center said. If it does so, Colorado State University hurricane researcher Phil Klotzbach said the Atlantic would be “3 for 3” in hurricanes becoming major this year, with Erin and Gabrielle both becoming major hurricanes.
The last time an Atlantic hurricane season’s first three hurricanes reached that level was in 1935, he said.
Doyle Rice and Dinah Voyles Pulver are national correspondents for USA TODAY, with decades of experience covering hurricanes, weather and climate. Reach them at drice@usatoday.com and dpulver@usatoday.com.