Most Unlikely Tornadoes

[Jeshua Everett]

I’m not sure if that would perfectly match the question but most people I met don’t realize that tornadoes could hit the mountains. There were a few instances of tornadoes hitting Great Smoky Mountains National Park and nearby areas, including behemoth 2011 EF4+ (there’s uncertainty if it was actually EF4 or EF5 according to researchers involved in this study due to its remote location but its still official EF4 by NWS). Some people were surprised about tornadoes hitting Smokies. I think it has more to do with people belief than conditions themselves

I'm often reminded of the 1987 Yellowstone tornado, or how the people of Waco thought the hills (some thought were ancient burial grounds) protected them from tornadoes before 1953.... While the damage survey of the Mayflower/Vilonia tornado seemed to show possible evidence that hills and ridges can effect the path and strength of a tornado, there's been instances where tornadoes just don't seem to care and occur at high elevations and in mountainous, rocky, hilly terrain. So maybe people who have witnessed tornadoes following a ridge in their area instead of tracking directly over it start to develop a belief that they won't ever go over the ridge? When in fact, we all know, a tornado very well can!

 

[Andy Wehrle]

Hi Steve, that's a great question. Keep in mind that the majority of the storm structure exists from about 2000 ft on up to 40,000 ft or more. So one way to get a weird storm situation is have a bunch of cold air at the surface, and bring in tons of rich Gulf moisture just above this cold layer, at about 2000-6000 ft above the ground, with cold air above that (above 10,000 ft).

It's not uncommon for this to happen in Texas and Oklahoma during the cold season, but it is rare when it produces tornadoes. One famous situation where this happened was the night of February 21-22, 1975 near Altus, Oklahoma. On that day there was a cold air outbreak in Oklahoma. Gusty north winds, temperatures of 36 degrees, but aloft it was very unstable. Thunderstorms developed and at least six tornadoes touched down around 2 am, one of them F2. Storm Data shows 3 people were killed around the Altus-Mountain View area with 70 injured.

This would have been a pretty scary situation to be in because it's night, it's overcast so you can't see much, and of course there's no good weather data. Since the situation was so unusual I'm not even sure that Gary England was on the TV.

...

Gary England *was* on TV, he wrote about this event in his book "Weathering the Storm: Tornadoes, Television and Turmoil." He went on air with a severe thunderstorm warning based on a call from a viewer in Altus describing how strong the winds were. Neither he nor the caller would have had any way of knowing it was actually a tornado.

 

[John Moore]

There was the Flagstaff, AZ outbreak - October 6, 2010. Flagstaff is above 7000' MSL, and at least one of the tornadoes was over significantly higher terrain. Two of them just missed the NWS office in Belmont - a few miles west of Flagstaff - leaving behind long tracks through the pine forest that looked like power line clearings.

The outbreak included a long track tornado and a 1km wide tornado, 4 EF2's, 1 EF3 out of a total of 9 tornadoes.

The same system caused two damaging supercells here in the Phoenix metropolitan area. The hail not only damaged cars, but also a lot of air conditioner condensers around town. I watched it from my office near the Scottsdale airport, and saw estimated 2" hail.

Wikipedia Link

 

[Jeff Wright]

Two come to mind. The Colton tornado with a very wide footprint from Grazulis Tornado Video Classics (nothat a wedge..)
The Nashville tornado was called a mesocyclone on the ground, was it not? That seems to be how the Tuscaloosa-B'ham twister of 2011finished up as.

Here is one question--what violent tornado had the lowest topped storm spawn it? The weakest storm to produce a tornado?

 

[Paul Knightley]

In answer to the 'weakest storm' - I can't quantify the weakness of the following, but I know the convection was pretty shallow:

Last year we had a very cold easterly flow across the UK, with showers forming in a kind of Lake-effect style - a stream of showers moved over SW England, and someone took this video of a stout funnel, which must have been very close to be a tornado (and probably was), from convection that can't have been more than 12,500 feet high (i.e. the tropopause was at this level) - indeed, the tops may have been lower! Note the snow on the ground too (this area of the UK doesn't get much snow, on average!).

Nearby sounding is below - note the strong speed shear in the lowest part.

 

[Jeff House]

We were returning from a March ski trip in Colorado. Kansas was outlooked for severe; so, I was hoping for a fun drive home.

Much earlier than I expected a rope dropped out of a high base near the Adams/Arapahoe Counties intersection. It was cool, but apparently we had moist enough upslope flow. Plus, Colorado gonna troll, lol!