The Science of Chasing Tornadoes

Tornado season begins in March, and while spotting twisters is not magic, some basic weather science will help you understand what to look for when severe weather threatens. Chief Meteorologist Steve Lanore explains in Part One of "The Science of Chasing Tornadoes."

A large tornado on the ground is one of the most terrifying natural disasters you might face. Around 1,200 tornadoes strike the United States each year. More than half of these show up in the spring.

Tornadoes are generated by severe thunderstorms. These begin with an updraft and downdraft of air, but sometimes the updraft becomes super-charged. Several factors can trigger the powerful rush of air like a cold front combined with low pressure and a strong jet stream.

Another factor is wind shear, which are winds blowing at various speeds and directions at different altitudes, and that can further boost the destructive potential.

Doug Drace has been spotting and chasing storms since the mid 1990's and explains what goes on in inside a potentially tornadic storm.

"The first visual clue that you're going to see from this storm is the very well defined rain foot that's coming out from the downdraft, which gives you the idea that there's a very strong updraft beneath the rain free base there,” Drace says.

That rain free base is part of what's called the updraft zone. This is the area of the storm that is most likely to produce tornadoes.

"Right here you can see a lot of the mid-level banding that's in this storm, you see, when you get banding like that, and it's tight, and it's almost spiraled looking, then you know that you're in a pretty strong area of wind shear, and the likelihood of a potential tornado is increasing at that point"

A tell-tale sign of trouble is the appearance of -what's known as- a wall cloud. These usually form under the rain-free base of the storm towards the back edge. Once a wall cloud starts rotating, that suggests a tornado could form at any time.

"If you can get a wall cloud you know, rotating really close to the surface, and you can see a lot of scud rising into it, the likelihood is a lot more, a lot greater, that you're going to get a tornado, whereas this (storm) appears to be just a little more elevated than a lot of the wall clouds that I've chased that have actually produced tornadoes," Drace says.

"It's dangerous, you think about getting near a Super cell that's 40,000-50,000 feet tall, producing hail up to the size of softballs, and winds of 80 miles an hour, not to mention extremely strong winds underneath the wall cloud, with strong rotation, just extremely dangerous."

Part 2

On Tuesday, Steve LaNore and storm chaser Doug Drace gave visual clues for spotting trouble in a thunderstorm. In part of two of our series, "The Science Of Chasing Tornadoes" we join the quest to capture twisters on tape, starting with one right here in Texoma.

Doug Drace was only a few miles way when video of a tornado that hit southern Oklahoma was captured May 7th, 1995. He saw the same tornado just before it hit Ardmore.

"It was a pretty incredible experience, I was a little bit scared my first time out, didn't have very good information, so I kept my distance probably about two or three miles from it"

But Doug hit the tornado jackpot on a West Texas chase last year.

"This circulation here became very intense and much lower to the ground, which was an indication that the storm was getting a lot stronger and possibly going to start producing larger and more destructive tornadoes. This is the same wall cloud actually producing a tornado now as it crosses the road. As you can see the circulation is extremely intense,” Drace says.

One problem is severe storm rubber-neckers. It has gotten much worse since the release of the movie "Twister".

"The first year I went chasing, probably each time I went out, I saw 20 or 30 people chasing, just die hard storm chasers; once the movie came out, the very same year, it jumped from probably 30 to about 500 people out there chasing"

Even though Doug is an experienced and sensible chaser, he says sometimes you have to take a few chances to unravel nature's mysteries.

"We're doing what we call a core punch on this, which is a very dangerous thing to do when chasing storms, but sometimes it's the only way that you can get close enough to the wall cloud to see if there's actually a tornado on the ground with it," Drace says.

"This is absolutely the classic "stovepipe" tornado, it's got an extremely large bulge in the center of it and it's very tall, the tornado as this point is probably about a quarter of a mile wide," Drace goes on.

"This was the largest tornado of the day. This was rated F5 tornado, over a mile wide, sometimes a mile and a half wide, and it's just a classic Texas Panhandle kind of tornado," Drace says.

"These were all fortunately out in the middle of nowhere; had we had a tornado outbreak like this through a populated area, say through the Texoma area or the Oklahoma City area, it would have been pretty bad, there were a lot of strong tornadoes that day, a lot of F3-F4 kind of tornadoes, including that one really large F5"

As for advice for those interested in storm chasing, Drace says, “First thing to do, is just get information; everything you need to know about storm chasing is available over the Internet; try and maybe get in contact with storm chasers, some will give you the time of day, some of them won't. The best thing to do is even try and set up a storm chase with someone who has done it."

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