Based on the evidence so far, the Washington IL EF-4 tornado is the strongest November tornado on record for Illinois since modern records began in 1950.
The EF-3 tornado in Gifford is possibly only the third tornado of that magnitude since 1950.
One of the other EF-3 tornadoes occurred on November 15, 1988, in Madison and St. Clair Counties. The other EF-3 tornado occurred on November 19, 1991 in Marion (Williamson County). There is some confusion about this event. While it is listed as an EF-3 in the NOAA Storm Prediction Center database, the Marion History Preservation site stated that at one point the NWS declared it to be a microburst. Another source said it was later decided to be an EF-3 tornado. I am going to consider the Storm Prediction Center database as the final word on that one.
Using a database from the NOAA Storm Prediction Center, I found 62 tornado reports from 1950 to 2012 for November in Illinois. Here is the breakdown by Enhanced Fujita-scale and the earlier Fujita-scale:
- EF-0: 19 cases
- EF-1: 23 cases
- EF-2: 18 cases
- EF-3: 2 cases
- EF-4: 0 cases
- EF-5: 0 cases
Note #1: older tornadoes were rated using the original Fujita damage scale. In 2007, the NWS has shifted to an Enhanced Fujita damage scale. Even though the damage assessments have changed to include more information, the intent is to still allow comparisons between older and newer tornado events. For the sake of this post, I am using the term “EF” to refer to tornado strength in both the original and enhanced Fujita scale.
Note #2: the 62 tornadoes in November for Illinois in this Storm Prediction Center database is lower than the 68 tornadoes in November for Illinois found in an earlier study from 1950-2010 using data from the National Climatic Data Center.