Tornado outbreak of November 21, 2019

The tornado outbreak of November 21, 2019, was a major, single-day tornado outbreak that affected much of the Midwest and Southern United States. Over the course of 8 hours, 79 tornadoes touched down across 7 states. The most powerful and deadliest of the whole outbreak was an extremely violent EF4 tornado that tore through the towns of Princeton, Charleston, Madisonville, and Sacramento, Kentucky, killing 24 people and injuring hundreds of others. Another notable tornado was an EF3 that tore through the north side of Effingham, Illinois, killing 10 people and injuring many others. Overall, 42 people were killed in the outbreak, over 570 others were hurt, and at least $2.1 billion dollars in damages was left behind.

Meteorological synopsis
On November 16, the Storm Prediction Center issued a 15% risk of severe weather for the states of Missouri, Illinois, Indiana, and Kentucky, valid for Day 6. Computer Models showed the possibility of a severe weather outbreak taking shape across these areas on November 21, although much uncertainty existed as to how this event would play out. Over the next day, the computer models gained better consensus, which in turn led to more confidence for the SPC. Instability was forecasted to increase along the cold front of an extratropical cyclone, which was, at the time, nearing landfall on the coast of Oregon. With more confidence gained, the SPC issued a 30% risk of severe weather for Illinois, Indiana, and Kentucky, with the 15% risk expanded into Arkansas and Tennessee, on November 18. High amounts of CAPE, wind shear, and other factors led the SPC to issuing the 30% risk.

Early on November 19, the SPC issued a rare, Day 3 Moderate Risk for Illinois, Indiana, and Kentucky. These 3 states were described by the SPC as having the highest potential for tornadoes. The SPC maintained the Moderate Risk for both Day 2 outlooks, with some slight expansions/reductions done. Strong Tornadoes were also first mentioned in the discussion for the second Day 2 outlook. High amounts of CAPE, destabilizing atmospheric conditions, wind shear, and a shortwave trough approaching the area was the basis for the upgrade.

Early on November 21, at 0600 UTC, the Storm Prediction Center issued a High Risk of severe weather for Illinois, Indiana, and Kentucky, with a 30% significant chance of tornadoes. The moderate risk was expanded into Tennessee, Arkansas, and Missouri, with a 15% significant chance of tornadoes. The SPC stated in the discussion the chance for strong, potentially violent, long-tracked tornadoes across Illinois, Indiana, and Kentucky. Additionally, very large hail and very damaging winds were also expected across the high and moderate risk areas.