The Fujiwhara Effect: What exactly is it?

What is soon to become tropical storm Helene is forecast to bring northern Illinois additional chances for rain this weekend. 

As of this morning, this tropical entity was centered south of western Cuba. The latest from the National Hurricane Center brings soon-to-be Helene into the warm waters of the Gulf, allowing it to be strengthen into a high end category 2, possibly reaching major hurricane status prior to landfall. 

The remnants of Helene are then expected to take an unusual turn to the northwest towards Illinois as they wrap around a separate upper-level low. This is a meteorological process known as the Fujiwhara effect. It's when two separate low pressure systems rotate around one another. 

 

Forecast models have been consistent over the past few days, "slingshotting" Helen's remnants into central Illinois Saturday morning. 

For the time being, a slight chance for showers in the forecast for Saturday with slightly higher chances in place Sunday into next Monday.