What do we know about the deadly tornado outbreak of last week?

The devastating tornado outbreak that visited Kentucky and Illinois overnight Friday into Saturday morning has left a tragically large death toll in its wake.

NOAA’s Storm Prediction Center posted this Day1 Outlook Moderate Risk almost 10 hours prior to the outbreak, showing possibilities for severe weather this evening into tonight from northeast AR/southeast MO into western TN/KY and southern IL. (Image credit: NOAA/SPC)

Officials estimated Sunday that more than 100 people may have lost their lives to this event, though the recovery of some survivors later in the day gave hope the number might be lower.

The severe outbreak was part of the same storm that gave Wisconsin a rainy (in the south) and snowy (in the north) Friday.

The storm emerged from the central plains around midday on Friday, and in the 12 hours from midnight Friday to midday Saturday its central pressure (one measure of intensity) dropped 13 mb — a notably strong rate of development. It was during this rapid development period that the several killer tornadoes were spawned as the cyclone’s cold front processed very warm and humid air that was originally located to its east. The front, as all dynamically active fronts are, was characterized by a vigorous circulation that forced the warm, moist air upward forcing deep cumulus clouds and severe thunderstorms to develop.

Though such severe tornado outbreaks are a relative rarity in December, the basic ingredients that made this event possible are not uncommon during winter. In fact, storms that deepen even more rapidly than this one did are common enough that a few such storms will likely populate every winter in the Central United States.

Thus, though it might begin to emerge in the press as an example of climate change wreaking havoc with the weather, such a claim in the immediate aftermath of the storms is an unfounded assertion and will require additional analysis to evaluate.

It should be mentioned that the National Weather Service had the development of these tornadoes in sight a couple of days before they occurred, and this expertise surely saved lives.

Steve Ackerman and Jonathan Martin, professors in the UW-Madison department of atmospheric and oceanic sciences, are guests on WHA radio (970 AM) at 11:45 a.m. the last Monday of each month. Send them your questions at stevea@ssec.wisc.edu or jemarti1@wisc.edu.

Category: Meteorology, Seasons, Severe Weather

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