Weather History: The July 15th, 2024 Derecho

Northern Illinois got hit with back to back significant weather events in July 2024. 

First, the flash flooding on the 13th-14th which we went into detail about yesterday. That was quickly followed by a long-lived and well-organized complex of thunderstorms (which would be later classified as a Derecho) on the evening of the 15th.    

 

This strong complex of storms brought widespread damaging winds up to 60 to 100 mph as well as many tornadoes to eastern Iowa, northern Illinois and northwest Indiana. Once storm surveys concluded, the National Weather Service confirmed 56 tornadoes, 32 of which occurred in the NWS Chicago's forecast area. This is the most tornadoes in a single severe weather event for their forecast area.

As a refresher, the term Derecho is rarely used as a thunderstorm complex has to meet a certain criteria to be termed one. It's a meteorological term that simply means a significant, long-lived wind storm. 

The word itself comes from the Spanish adjective for straight or direct. The damage path has to be at least 250 miles which includes wind gusts of at least 58 mph and several 75 mph+ gusts. Northern Illinois sits in a region where derechos are a little more common, happening once per year!