Breakdown: Why December Tornadoes aren’t rare & not usually very strong

Published: Dec. 27, 2021 at 12:36 PM CST|Updated: Dec. 27, 2021 at 1:06 PM CST
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MEMPHIS, Tenn. (WMC) - When many of us think of late fall and winter, we may think that means severe weather is over, however that doesn’t stop tornadoes in the central and southern United States. Sometimes it can be the culprit as the cold air collides with warm, humid air that sometimes rides north from the Gulf of Mexico.

December tornadoes are not uncommon but the devastation and long tornado tracks that impacted northest Arkansas, Missouri, Tennessee and Kentucky was a rare occurence and on a another level entirely. The strength and long track tornadoes that happened were rare but not just for December tornadoes but for any time of year. There were six states total states affected by the tornado outbreak on Dec. 10 & 11th, which were Arkansas, Illinois, Kentucky, Missouri, Mississippi and Tennessee on Friday night and early Saturday.

On average, about two dozen tornadoes form in the Lower 48 states each December. Most of them occur in the western Gulf Coast region and lower Mississippi Valley. Louisiana, Texas, Arkansas and Mississippi are particularly vulnerable. December tornadoes can be violent but normally, they aren’t. On December 10, it was a powerful storm system that approached the central U.S. from the west. The same system brought heavy snow to the colder West and northern Midwest, meanwhile the South had temperatures in the upper 70s to low 80s which broke several records for warmth.

Five Deadliest tornado outbreaks in December

  • Dec. 5, 1953, Vicksburg, Miss., tornado, which killed 38 people, which held the record for the deadliest before the recent Quad-State tornadoes
  • New Year’s Eve, December 31, 1947 in northwest Louisiana, 18 were killed.
  • December 23 and 25, 2015 -northern Mississippi and Middle Tennessee 13 fatalities
  • Dec. 26, 1916, Central Arkansas 12 died
  • Dec 16, 2000 Tuscaloosa Alabama & surrounding counties, 11 fatalities

None of these events of the past were as deadly and destructive as what happened in the Quad-State tornadoes.

It was first thought that the Quad-State tornado, was one single tornado that may have carved out a path of up to 250 miles across the affected areas which would have surpassed the March 18, 1925, tornado event which track 219-mile across Missouri, Illinois, and Indiana. However, storm surveys found that the path was mostly composed of two distinct EF4 tornadoes, with a part of the path between the two EF-4 twisters over northwestern Obion County Tennessee being from three separate, weak tornadoes. Although it may have not broken the record for the longest ever, The National Weather Service (NWS) has given the large tornado that ripped through western Kentucky on Dec. 10 a preliminary damage rating of an EF-4 with a path length of 165.7 miles and estimated peak winds reaching 190 mph. The tornado’s track qualifies it for the top 10 longest tornadoes, according to NOAA Storm Prediction Center data since 1950. It is also the longest tornado on record for the month of December.

The recent Quad-State tornado was rare reaching a max EF-4 rating and had a long track. Since 1950, there have only been 19 F/EF4 tornadoes in the U.S. in December and only 2 F/EF5 tornadoes. The last EF4 tornado to strike the U.S. during the month of December was during the Christmas Outbreak of December 2015. The last EF5 tornado to strike the U.S. during the month of December was in 1957.

In December, the amount of energy available to storms is usually limited, which is why violent tornado outbreaks aren’t common. Friday Dec 10, 2021 was different, with record-setting temperature. Highs were 20 to 30 degrees above normal. In the Mid-South highs were in the 80s which is more common in April. One of the other main ingredient was, wind shear which is also in place. Wind shear is the turning of winds with height. Shear can be caused by the jet stream, which separates cold air from warm air. The jet stream which can migrate south and did just that into the central states and collided with the springlike environment, which was one of the causes of the tornado outbreak. Many other atmospheric elements contributed to the severity of the event, but it would not have been possible without the record-setting warmth.

The Quad- State December tornadoes struck at night and nighttime tornadoes are typically more deadly. More fatalities tend to happen with nighttime tornadoes because people don’t get warnings when they are sleeping. Storm spotting is harder at night and during the day more people are at work and in sturdier structures.

Be sure to have several ways to get warnings, even when you are sleeping. Stay with the Action News 5 First Alert Weather Team.

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