It’s called the Fujiwhara effect after a Japanese meteorologist, Dr. Sakuhei Fujiwhara, who first described it in 1921. It’s a fascinating interaction between two nearby tropical cyclones (or other vortices like low-pressure systems). Here’s how it works: The Basics When two tropical cyclones form close enough to each other (usually within about 800–900 miles), their circulations begin to interact. Instead of moving independently, they start to rotate, or orbit, around a common center point betw

Once inland, Helene will be pulled the northwest, rotating around an upper low over Arkansas. This is known as the "Fujiwhara effect", which is pretty unusual at this latitude. The tropical system and the upper low will basically rotate around each other. Scroll down for my long post with details about the tropical situation. | James Spann