On December 10-11, 2021 a historic tornado outbreak occurred in the U.S. mid-South, with 69 confirmed tornadoes and 90 fatalities. This was the deadliest December tornado outbreak in U.S. history. This swarm of tornadoes included a violent series of EF4 tornadoes (winds to 190mph) that cut across Arkansas, Tennessee, Missouri, and Kentucky, along a path totaling 246 miles. The thunderstorm that spawned these long-track tornadoes has been termed the Quad State Supercell. The first figure (Figure 1) shows the swarm of tornado (red dot) and damaging wind (blue dot) reports. These are layered on top of the "convective outlook" for the day, which uses a tiered system of severe weather risk categories (marginal, slight, enhanced, moderate) as issued by the NOAA Storm Prediction Center. The track of the Quad State Supercell shows up within the innermost red zone labeled MDT, which was the highest risk issued for the region that day. It's shown by the line of closely spaced tornado reports oriented from southwest to northeast, beginning in far northeast Arkansas.
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