Hurricane Helene is expected to make landfall in the US on September 26 as a Category 4 storm with winds of up to 210 km/h, according to the latest storm news from USA Today.
Hurricane Helene is forecast to be one of the most aggressive and rapidly intensifying storms in history. Helene's rapid escalation from a tropical depression with the potential to strengthen into a tropical storm to a Category 3 hurricane on September 24 is unprecedented for a system forecast by the US National Hurricane Center, according to USA Today.
"They've never forecast a major hurricane in 60 hours with a subtropical system. The whole forecast is also substantially faster than any 36- to 48-hour forecast for a tropical depression," said Sam Lillo, a meteorologist and software engineer at DTN Weather.
Hurricane Helene is expected to bring heavy rain when it makes landfall in the US due to the Fujiwhara effect, according to USA Today. The Fujiwhara effect - which describes two adjacent storms attracting each other - is considered the most delicate "dance" in meteorology.
Hurricane forecast models show that as Helene moves through Florida into the southeastern United States, "the storm will experience a Fujiwhara interaction with a low-pressure trough over the Ozarks," the National Weather Service in Shreveport, Louisiana, said.
"This essentially means that the remnants of Hurricane Helene after making landfall in the US will move near the low pressure trough in the Ozarks. The remnants of the storm will circulate around the low pressure trough before being absorbed by the low pressure trough to form a larger closed trough," the weather agency said.
"This phenomenon is extremely rare at this latitude," noted KATV meteorologist James Bryant.
Forecasters say the Fujiwhara interaction between Hurricane Helene and a low-pressure trough in the Ozarks will produce heavy rain, with the potential for flooding in parts of the central and southern United States and Ohio over the next few days.
The Fujiwhara effect occurs when two storms move close enough together to form a violent “dance” around a common center. Experts say the effect occurs when the storms are about 1,500km apart.
This double storm phenomenon was first confirmed by Japanese meteorologist Sakuhei Fujiwhara after observing two interacting storms in the Pacific Ocean in 2021.
The Fujiwhara effect could make hurricane forecasting more difficult. Typically, predicting where a hurricane will make landfall is difficult in weather forecasting. However, the Fujiwhara interaction could make this process even more difficult.
The question is how strong the storm, or secondary depression, will become. If the depression gets stronger, it will push Helene's path closer to the narrow strip of Florida.
If the depression weakens, Helene could have more impact along Florida’s Big Bend region. Forecasters will see clearer details of those in the next 24-36 hours.
