Living for the chase

Dr Jana Houser, Associate Professor, Department of Geography, Ohio State University

It is late May. The morning air is thick with moisture. I breathe in the smell of damp grass and clean air. A moderate breeze out of the southeast blows through my hair, scattering strands across my face and my shoulders. It’s going to be an exciting day for severe weather in the Great Plains. I can sense it. Some days just have that feeling. It is tangible, albeit not exactly scientifically explainable.

It’s 9:00am CDT. Time to check the models. I pore over the data. Satellite observations, radar data, surface observations, upper air profiles, numerical forecast output – collectively these tools inform me where the conditions will be most favourable for tornadic storms today and where storms may (or may not!) fire. Starting out in Norman, Oklahoma today, we’re looking at a local chase, targeting somewhere a little west of Oklahoma City, along the eastward advancing dryline – a favoured region of storm formation where dry, hot air originating from the high terrain across Central Mexico intersects warm, moist air streaming northward from the Gulf. Today we aren’t in a hurry. Sometimes, we would have been on the road by 10am. It’s now noon. I look up into the sky and see a horseshoe vortex, a small, rotating cloud tendril shaped like a U. A lucky charm perhaps? I’d like to think so. I climb into the driver’s seat of the rapid-scan, X-band Polarimetric, mobile radar truck (RaXPol) and we are off, headed northwest to get in position for convection initiation, and hopefully to ‘catch’ a tornado. Not all chasing is the same. Or, perhaps, more appropriately, not all chasing is done with the same intent. At least, not exactly. Yes, I do chase in part for the excitement. I chase because I am captivated by the dichotomy of an atmospheric phenomenon that is delicate and beautiful and yet can inflict massive destruction. I chase because I am drawn to the simultaneous power and fragility of the atmosphere. Chasing storms has been a dream of mine since childhood. While some kids were talking about being firemen or teachers or ballerinas, I was outside on my back deck pretending to be the TV meteorologist, watching the Weather Channel religiously.

But I also chase for the science. I take instrumentation out into the field and collect data on storms that are capable of producing tornadoes, and ideally, on tornadoes as they form, intensify, then ultimately decay. I am not out to sell video footage or to get dangerously close. I am seeking to answer questions such as: “Does the rotation that turns into a tornado begin in the cloud or at the ground?” “What is the source of the rotation that ultimately ends up in the tornado?” “Why does one storm produce a tornado while a neighbouring storm less than 50 miles away does not?” “Can we discern any subtle cues from the environment that will distinguish between an atmosphere conducive for tornadoes versus one that is not?” I want to explain it. I want to put a story together, to complete the puzzle. But the answers keep eluding me (and, let’s be honest, they have been eluding the meteorological community for decades!) It is so logistically challenging to be in the right place at the right time to collect the data you need. Numerical simulations are helpful, but they have to simplify the atmosphere. Tornadoes are small and short-lived, making them very difficult to sample. And the Plains are big, and Mother Nature is fickle. Most chases end with no tornadoes.

Back to the moment. It’s 3:00pm CDT. The cap is breaking. That’s meteorological lingo meaning storms are starting to form. I can see the bubbly white cumulus congestus clouds on the satellite data, and visually off to my southwest. The first radar echoes are showing up. We find a nice, flat, open spot with a clear line of sight to our storm, and we start collecting mobile radar data.

The sky darkens. Daylight turns to an eerie, unnatural twilight with only a thin ribbon of light on the far western horizon. The clouds billow up vigorously, roiling on their ascent. The strong turning of the winds with height makes the updraft of this storm rotate. Some storms have spectacular structure as a result of these rotating updrafts, or mesocyclones – layers of clouds, striations, some even look like mother ships from an alien planet. This one, however, is just black. Featureless and mean. The cloud base starts to lower on the southwestern side of the storm. A wall cloud, the possible predecessor of a tornado, is forming as the updraft ingests rain-cooled air. It is still a bit far away but I can see tendrils of clouds descending from the wall cloud, briefly spinning and then evaporating as if moving to some strange cloud dance. Then I see it! A dust swirl on the ground! Tornado! Turning my eyes higher to the wall cloud, I don’t see evidence of a well-defined funnel, but debris is definitely being picked up at the surface. Our radar is scanning the storm, penetrating past what my eyes can visually see. It detects the strong rotation near the ground first as well. For about one-and-a-half minutes, that’s all there is! Then, over a brief 30-second interval, the rotation is rapidly drawn upward, and a full-fledged tornado is born! We watch in awe and wonder, as the tornado rapidly transforms into a large mile-wide wedge. It is approaching our location. The radar is detecting winds close to 300mph, a mere 100 feet or so above the ground. Thankfully, the tornado is wreaking havoc over mostly empty fields and shrubby grassland. This one is ferocious! It is time to make a decision. We need to bail. It takes at least five minutes to pack up the radar and hit the road again, and this thing is barrelling at us fast! Traditional chasing logic would have us move south. We are on a north-south oriented road. But this tornado and the storm that is producing it have turned to the right, and hard! That means that its motion is more easterly, and perhaps even south-easterly. We opt to head north, back to interstate 40, and then go east, toward Oklahoma City. This turns out to be a very wise strategy, as we likely would not have beaten the tornado across our south road option. That could have been catastrophic! Despite the fact that your eyes focus on the descending funnel cloud, the strongest rotation tends to be concentrated at the surface first, and then rapidly either extends upward, or simultaneously converges in the layer of air between the ground and the cloud base.

Our chase this day ends in a traffic jam, trying to get through Oklahoma City at rush hour, in the midst of a panicked public still reeling from an EF5 tornado that devastated Moore a mere 11 days earlier. That tornado that we sampled? It became the widest on record, exceeding 2.6 miles from end to end! Thank heavens it dissipated before entering the more populated western suburbs of Oklahoma City. Sadly, several of our colleagues ended up losing their lives by deciding to go south on that road we could have very easily taken as well. The data we collected went on to inspire a study which confirmed that many, if not most, tornadoes forming from supercells, develop not from the cloud to the ground but from the bottom up. It was a day to remember, for sure. Forever. Chasing is equal parts skill and luck. You have to know what you’re doing. You need to make wise choices, and anticipate storm behaviour before it happens. But there are so many circumstances out of your control as well. Chasing is an unusual dichotomy of hurry up and wait. Hurry up! Get to your target area! Wait for storms to form. Wait for the moisture to return. Wait for the winds to back. Then hurry again! Feverishly, try to catch up with a storm that knows no road geometry, crosses rivers easily, and moves with the power of the wind. Hope you make it to a place with good visibility just before the tornado forms. So many things can go wrong. So many things do go wrong. But, perhaps, that is what makes the chase all the more gratifying when you catch what you’re looking for! The old adage ‘you have to taste the bitter to enjoy the sweet’ definitely rings true. I keep chasing. Somehow, I can’t get enough. There are more tornadoes to see, questions to answer, and mysteries to unravel. And even if I knew everything, I would still pursue the chase.

We are delighted to share some of the fantastic winning and shortlisted photographs from the Royal Meteorological Society’s annual competition, on these pages, on our front cover, and on articles throughout the magazine. See www.rmets.org/2022-wpoty-winners for more information.