Weather explainer: What led to so many deadly widespread tornadoes during December

National News

RALEIGH, N.C. (WNCN) — Tornadoes in December are not uncommon, but Friday night’s outbreak may have produced some of the worst December tornadoes, and possibly one of the worst in the state of Kentucky’s history.

The overall weather set-up involved warmer than normal temperatures and windy weather south of a warm front. Remember that thunderstorms need moisture, instability, and a source of lift to develop.

The humidity was coming up on the breezy south winds which in turn also warmed temperatures and helped create the instability and energy storms need.

Finally, a strong cold front was trailing off to the west and as it, and the entire weather system, started moving to the east, it was the “source of lift” that forced strong updrafts in these thunderstorms.

There were other atmospheric factors in play as well such as strong wind shear, or the turning of winds with height, that created the strong rotation needed within these storms to create tornadoes.

What made this outbreak so deadly was a combination of violent, long-track tornadoes, and bad timing. Nighttime tornadoes are more deadly as people are typically in bed and not paying as much attention to the weather.

In Kentucky alone, 22 were confirmed dead by Saturday afternoon, including 11 in and around Bowling Green. But Kentucky Gov. Andy Beshear said upwards of 70 may have been killed when a twister touched down for more than 200 miles in his state and that the number of deaths could eventually exceed 100 across 10 or more counties.

The death toll of 36 across five states includes six people in Illinois, where an Amazon facility was hit; four in Tennessee; two in Arkansas, where a nursing home was destroyed; and two in Missouri.

If early reports are confirmed, the twister “will likely go down perhaps as one of the longest track violent tornadoes in United States history,” said Victor Genzini, a researcher on extreme weather at Northern Illinois University.

A weather radio can be a life-saving measure in nighttime events, as long as the volume is at a loud enough level that it will wake you up from sleep with enough time for you to shelter in a safe place.

— The Associated Press contributed to this report

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