I’ve been blogging about some of the more memorable weather of 2021 so how ironic that just last Friday would be the MOST memorable severe weather outbreak of the year.
The cover photo shows twin tornadoes last Friday evening in Bay, Arkansas (just southeast of Jonesboro) that began what would be a long and dangerous night as tornadoes tracked all evening from Arkansas to Kentucky, thus called ‘long-track’ tornadoes. KAIT8 Chief Meteorologist Ryan Vaughn posted: “This pic is when the long-track tornado was just cranking up. Yes, it started as two separate tornadoes. Pic is from Angie Burgess from Bay, AR, looking northwest. I just thought you guys would want to see how it started. For the hour prior to this, it had produced intermittent touchdowns. Pretty sure it was on the ground from this point forward though.”
You can see from the Storm Prediction Center’s map that high wind and hail reports even began in northeast Texas and then a total of 464 Severe Weather reports came through with 69 of those for tornadoes (often the same tornado hitting different communities):
The full report is here. This kind of outbreak is unusual for December, normally reporting the least number of tornadoes and not the kind that stay on the ground for hours. But what is not unusual is tornado formation when very cold air meets very warm and humid air along with a strong set up for winds in different directions. WDIV meteorologist Paul Gross posted this synoptic map showing the contrast and below that I’ve made it simple to understand:
It’s easy to see the 20° and 30° temperatures on one side and the 60-70s on the other.
WOWK meteorologist Joe Fitzwater really got going with the pencils, and while I know you’re seeing a bunch of squiggly lines, if you take time to look at this analysis you can really see how quickly the temperatures cooled down behind the front from 60° to 40° over just a few miles. The faster the cooling, the faster the warm air is forced up into that cool air forming huge and dangerous thunderstorms. This causes an explosive release of energy. The hail reports alone would tell you the air above is very cold.
And that low pressure storm had barometric readings akin to a healthy tropical storm easily producing 60-70 mph winds, which is very close to hurricane strength. Also note that those very fast winds are from almost all directions: southeast ahead of the front, southwest along the front, northwest and north behind the front. Those different winds are what cause the air to turn and twist resulting in those tornadoes.
Are we in for more?
This setup for long-track tornadoes is, thankfully, rare. But the amazingly warm December we’ve see across the country is also rare and those contrasts of extreme warm versus extreme cold are certainly a key ingredient. In fact, we seem to be in the middle of one of our warmest Decembers on record, already hitting 85° twice at Bush Airport, which ties our all-time record high from Dec. 3, 1995.
We’re in for another warm week this week with low 80s starting tomorrow through Friday and long-range models are forecasting another warm period the end of the month -- it’s way out there, but even 80° for Christmas Eve and Day! We’ll see. In the meantime, we’re learning that dangerous weather knows no month, so always stay weather aware!