Storm Chasing Diary: More Tornadoes

Gary Hart Photography: Large Tornado, Morton, Texas

Wedge Tornado, Morton, Texas
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A month ago I shared an image of my very first tornado. As exciting as that experience was, it turns out that was only the beginning….

When a large supercell reaches maturity, the urgency among storm chasers seems to ratchet up exponentially. So one indelible lesson from my first storm chasing experience is that there’s no time to bask in your success, no matter how spectacular, because there’s potentially something at least as good down the road—and we’re on Mother Nature’s schedule.

While chasing supercells is incredible for many reasons, it seems everyone’s number one storm chasing goal is a tornado. But as thoroughly monitored, measured, and studied (and chased!) as tornadoes are, there’s still a lot to be learned about the how, when, and why of their formation. Why does one storm kick out multiple tornadoes, while the next similarly dynamic storm produces none? And why do some tornadoes form and disappear in seconds, while others grow to be a mile or more wide and stay on the ground for hours? Though the answers to these questions and more will undoubtably save lives, they remain frustratingly elusive. Fortunately, despite the lack of life-saving perfect insight, the general mechanism behind tornado formation is understood well enough to already be making a difference.

The action kicks off when daytime heating sends warm, moist air rising into increasingly colder, denser air. Since air cools as it rises, and cool air can’t hold as much moisture as warmer air, condensation occurs and we get clouds. Condensation releases energy that warms the air. The atmosphere is said to be unstable when the heat created by condensation is sufficient to keep the air rising. Lacking instability, the convection driving updrafts shuts off, but as long as the air is unstable, the updraft will persist. Of course what goes up, must come down—eventually the rising air is wrung of its moisture, allowing it to cool enough to descend, and a downdraft is born.

Still, while every thunderstorm forms through some version of this process, most don’t turn into tornado breeding supercells. For that, other atmospheric tumblers must click into place.

Most tornadoes are born in supercells—storms powered by a very powerful rotating updraft called a mesocyclone. A mesocyclone forms when a storm’s updraft encounters wind shear: different wind speed and/or wind direction at different heights in the atmosphere impart a spin to the rising air. Shear-induced spin actually starts horizontally, like rolling logs, but is soon tilted toward vertical by the overpowering updraft. When the vertical column of rising, spinning air reaches the ground, a tornado is born.

On the afternoon we saw our tornadoes, when the first one disappeared and its storm started shifting east, our group quickly loaded back into the vans and raced to get back ahead of it. The goal isn’t to be directly in a cell’s path, it’s (usually) to position ourselves adjacent to and in front of its path, so we can watch the action move across our field of vision.

Storm chasers generally avoid urban areas because traffic, stop signs, and stoplights can be very difficult to navigate, and buildings and trees obstruct views. While chasing tends to be easier in the wide open countryside, the downside there is fewer roads—even if we know exactly where we want to be, that knowledge does little good if there’s no road to take us there. And because many roads in these rural areas are unpaved they could quickly be rendered a completely impassable swamp by a downpour—you definitely don’t want to be spinning your tires in the mud with a large tornado or grapefruit-size hail bearing down on you.

We lucked out this evening. We got our supercell, and roads we found were paved and seemed to be laid out specifically to get us in the right place to continue our pursuit. But we quickly found that we weren’t the only ones appreciating the roads that evening, and as we approached our next target vantage point, we found both shoulders teeming with a veritable fleet of chase vehicles.

This diverse assortment included ordinary street vehicles (think generic rental cars), large passenger vans filled with chase groups like ours, trucks with massive tires, and clearly single-purpose storm-chasing beaters that appeared to sport their hail-inflicted wounds with pride. Some vehicles were outfitted with external cameras, weather stations, or satellite dishes (or all of the above). Of all the cars chasing that evening, I think the highlight for me was Reed Timmer’s heavily armored Dominator. (This is the storm chasing equivalent of a celebrity sighting—if you ever watched “Storm Chasers” on Netflix, you know what I’m talking about.)

Whirl, Tornado Near Morton, Texas

Navigating this stretch, it was impossible to drive more than a few car lengths without having to swerve or brake for a pedestrian bolting across the road. Rather than seek the perfect parking spot, we grabbed the first open spaces we found and raced on foot to a fence separating the road from a recently plowed field. Even though we were outside the most intense storm activity, the wind here was still quite strong, and the clouds overhead seemed poised to open up. Of course all this activity only added to the thrill of the moment.

Soon our trip leader Chris directed our attention across the field and a little west (left), maybe 1/2 mile away, to the tornado precursor we hope for our: a descending, rotating wall cloud. While promising, this isn’t a sure thing, but it wasn’t long before the first funnel dropped. We all watched, and held our breath, as the tornado approached, then appeared to pass just behind, a small farm. Over the next few minutes, a couple more tornadoes spun up and vanished in fairly short order.

Then our attention turned to an expanding wall of brown dust directly across the field. At first there was so much dust, it was difficult to tell exactly what was going on there, but it certainly looked promising. It wasn’t long before everything clearly organized into a very large wedge tornado that was on a different scale from what we’d seen so far, with the inflow feeding it clearly defined by the dust it sucked up.

I only managed a half-dozen or so frames before the wind picked up and approaching hail chased us away; shortly thereafter, the road network failed us and we lost track of the tornado. But given its size and organization, we weren’t surprised to learn later was that this tornado was on the ground for nearly 30 minutes, traveled over 10 miles, and eventually expanded to at least a mile wide. According to some (unverified) reports, it was up to 2.2 miles wide, which would make it the largest tornado ever recorded in Texas. The National Weather Service rated it as an EF2, with winds around 125 MPH. Fortunately, whatever its size, the tornado kept to wide open farmland, which limited its damage to a few downed trees and power poles.