TAMPA, Fla. (WFLA/WKBN) — A phenomenon known as the Fujiwhara effect could impact Tropical Storm Helene‘s path as it churns northward.

The Fujiwhara effect is when two areas of low pressure attract each other, when they normally would repel each other, according to NewsNation affiliate WFLA meteorologist Eric Stone. In rare instances, two storms can combine to create a larger one instead of two smaller ones, according to the National Weather Service.

The National Oceanic and Atmospheric Administration defines it as “a binary interaction where tropical cyclones within a certain distance (300-750 nautical miles depending on the sizes of the cyclones) of each other begin to rotate about a common midpoint.”

“It’s something that you just don’t see — it’s very rare,” Stone said. “Usually two lows will repel each other, but in this case, they’re attracting each other.”

Stone said the high pressure system over Florida will also help steer the system north, something that was not present during Hurricane Ian.

“What’s going to happen is Helene is going to be sucked up — guided and attracted to that upper level low,” Stone said. “That’s what’s going to keep this thing moving more northerly than more northeasterly.”

“Then what happens is it actually gets sucked into that upper level low, and the two systems will be combined into one,” he said. “By that time, it’s not going to be a strong storm, so it’s not like we’re going to have this super powerful storm, but it’s a really cool effect.”

The National Weather Service said one example of the Fujiwhara effect was in the East Pacific in 2017 with hurricanes Hilary and Irwin.

When was the Fujiwhara effect discovered?

This phenomenon was first identified by Japanese meteorologist Sakuhei Fujiwhara, who observed two cyclones interacting in the Pacific in 2021.

Since then, the effect has been observed numerous times from storms as small as tornadoes, but it is still fascinating when it happens with a tropical system.

The Fujiwhara effect could make forecasting difficult

Forecasting where a hurricane is going to make landfall is always difficult; however, the Fujiwhara effect could make this process frustrating. The issue is determining how strong the secondary area of low pressure will be.

If it is stronger, then this will pull the track of Helene closer to the Florida Panhandle. If it stays weak, then Helene could make more of an impact along the Big Bend area of Florida. These details will become more clear in the next 24-36 hours.