Based on an initial damage assessment of the tornado that touched down in suburban Naperville on Sunday night, the National Weather Service estimates that the twister was an EF-3 on the Enhanced Fujita Scale, packing wind speeds of nearly 140 miles per hour.
The NWS conducted a damage survey of the area on Monday morning after the tornado struck the area. According to the service, the tornado touched down near Naperville just after 11 p.m. Sunday and ended near Willow Springs.
The team has surveyed damage in Naperville and Woodridge, and will work its way through Darien, Burr Ridge and Willow Springs in coming days.
The damage the team surveyed was “consistent with wind speeds corresponding” to an EF-1 or EF-2 tornado, but one pocket of damage, located near Princeton Circle in Naperville, is consistent with EF-3 rating, indicating that the twister was packing wind speeds between 136 and 165 miles per hour.
The Enhanced Fujita Scale, which was brought into use in 2007, uses estimated wind gusts in three-second increments to determine the strength and power of a tornado.
All estimates are preliminary, and additional information about the path, length and width of the tornado will be accrued in coming days as the surveying crew continues its work.