HAIL TO THE CHIEF: Rare Tornado Outbreak Explained
Reports locally of strong wind gusts and small hail certainly doesn’t compare to the extensive tornadic destruction that took place in a number of towns near the Peoria area.
About half of the 80 tornadoes that struck the Midwest on Sunday, November 17, 2013 were reported in Illinois. Once the National Weather Service survey is done for the state, it will likely lead to the largest number of tornadoes ever recorded in the month of November.
Tornadoes in the state of Illinois are rare but they can happen. Since January of 1950 there have been over 500 tornadoes reported across the 23 counties in the state. 11 of those occurred in November. This means that the month of November accounts for roughly 2% of the yearly activity.
Such strong storms in the Midwest are rare this late in the year because there usually isn’t enough heat from the sun to sustain thunderstorms.
However, the temperatures on Sunday did reach into the 60s and 70s, which is warm enough to help produce severe weather like strong winds and small hail.
The lack of heating at this time of year can also be compensated by the wind structure or shear that occurs from the surface to the upper atmosphere. Typically around this time of year, these winds can be stronger compared to the winds that take place in the summer.
On Sunday, surface winds from the south interacted with the strong jet aloft coming from west-southwest. When that combined with the cold air spinning around the core of the system, we had the makings of a towering line of intense, tornado-producing thunderstorms.