November 17th Severe Weather Outbreak: An In-Depth Look
A powerful low pressure system moved to the northeast as it tracked across south-central Wisconsin; by the afternoon on the 17th the low had deepened to 987 mb. At the same time, a potent cold front extended southward from this low across central Illinois. This boundary moved eastward through the afternoon and early evening hours, with severe thunderstorms firing along it. The strong southerly winds ahead of the front allowed a warm, moist and unstable air mass to surge northward into the Ohio River Valley and Midwest. Winds also veered and increased substantially with height, creating plenty of wind shear - a key component of most tornadic severe weather outbreaks.
Event Facts and Statistics:
This event was the deadliest and most violent tornado outbreak on record during the month of November in Illinois, with at least 6 fatalities reported. Over 100 tornado warnings were issued by the National Weather Service during this event, with over 50 tornadoes being confirmed across at least five different states (IN, MI, OH, KY, & IL). The EF-4 tornado that tore through Washington, IL was only 1 of 20 EF-4s to occur during the month of November dating back to 1950, and was the third most northerly November EF-4 ever observed! In total, there were 25 tornadoes in Illinois, with 14 being significant (EF-2 or stronger). Aside from these violent and destructive tornadoes, strong super cells also produced large hail (up to golf ball size near New Lenox and Rockford) and strong gusty winds. Two tornadoes in particular, struck the immediate Chicago Metro Area, which have been documented below.
Frankfort and Coal City Tornadoes:
The Frankfort tornado began around 12:42 PM approximately 3 miles southeast of Manhattan, IL and tracked northeast for about 5.5 miles. The path width was around 200 yards and maximum winds were 125 mph, making it an EF-2. The tornado then weakened and lifted at 12:48 PM, 2 miles SSW of Frankfort, IL. Luckily no known injuries were reported from this tornado. The Coal City tornado touched down at 12:22 PM, about 3 miles SSW of Coal City, IL. It then tracked northeast for 12.9 miles with a path width of 200 yards. This tornado was also classified as an EF-2, with reported winds of at least 125 mph. The tornado finally dissipated at 12:33 PM, 4 miles NNE of Wilmington, IL. Unfortunately there were at least 3 injuries reported from this storm.