Earth & sky

Gallery: Stormchasing >>

Few things could dislodge me from watching the World Cup; stormchasing is emphatically one of them. 

Stormchasing. It has multiple meanings. Mostly, of course, we associate it with the semi-crazies who take risks – some greater, some lesser – in their quest to see a tornado. But as a veteran of three chase weekends over the past 7 years (ie not a veteran at all), I have to observe that much time is spent being chased by the storm, and not the other way around.

So it was this past weekend. I headed out to Minneapolis early Friday morning with Anton and our dear childhood friend Anna (Claude) Bailey. Anna left her husband Prospero and their four kids with friends in Charlottesville to come on this adventure. Anton’s wife Tracie joined us on Saturday morning. Anton had been crowing for a week about how it would be a perfect weekend to chase, and the moment we drove out of the Twin Cities it became apparent that he was right.

Chasing is one of those “physical chess” sorts of activities. Played on an enormous board - the vast flatlands flanked by the Rockies to the West and the Appalachians to the East, Texas to the South and Canada North - it’s as much an intellectual challenge as anything else. Radar and satellite are undoubtedly allies, but ultimately it’s a game of experience and judgement. I’d say Anton has both in ample supply.

FIrst, a little Science:

The supercell thunderstorms that form here are unlike those anywhere else in the world. What makes them so amazing is the particular set of dynamics that converge to create them. I’m way oversimplifying here, but as I understand it, moist air from the Gulf (currently the Oily Gulf) drifts up from the South and flows beneath a layer of drier warm air that streams eastward from the Rockies. This creates something called an inversion layer, sort of a “cap” that traps the saturated, sticky air down near the surface, which gets heated by the sun which bakes the moisture out of the rich land below, and thus gets stickier and more saturated. Clouds form, and after many attempts (ie impressive looking cumulus clouds that look formidable but then evaporate), one of them manages to punch through the “cap” - once it’s through, moisture starts rocketing up through breach, and a serious, enormous thunderhead develops. The updraft in the “core” of the storm can be of incredible velocity - imagine a huge, wide blast of air shooting directly upward at speeds that can reach to 150mph! 

As all of this happens, the cloud gets “organized”. Different parts of the cloud perform different functions. There’s the core, blasting moisture up into the high frozen atmosphere, where it forms hailstones that then fall, picking up more moisture, only to be whooshed back up  over and over again until they’re actually heavy enough to fall to earth. There’s the menacing bank of cloud that heralds the edge of the storm, very low to the earth and extremely dynamic and active in that it looks like it’s boiling and seething. There’s the anvil, way high above, the very top of the storm, which can be twice as high as a commercial plane flies (65,000+ feet).

And then there’s this thing called rotation. This happens when the updraft rises through higher altitude winds, coming from a different angle, start to rotate the entire updraft in the storm in a circulation known as a mesocyclone. Growing by positive feedbacks, the mesocyclone picks up velocity and also tightens up - sort of like how an ice-skater brings her arms in closer as she spins until she’s just a blur. Tornadoes, if they occur, will grow within the core of these circulations -- yet the majority of supercells fail to produce tornadoes for reasons that remain unknown. 

There’s more to it, of course, but I think I’ve hit the main points (thanks to Anton for fact checking this section)

Back on the Ground

We set off chasing, down from Minnesota into South Dakota. Hazy, broken sun, and very humid. Burgers at a smoky cafe; the notice board covered with local announcements - No Alcohol or Guns at Saturday night’s concert, if you please. Small towns, many billboards and signs relating to Jesus and God and Abortion (“Dr Henderson rips babies limb from limb here”, read one of them). Anton’s watching a developing cloud but decides we should get heading west. We sit at a lake; pelicans fly over in a huge formation. Anton decides we’ve gone too far, and should get back to the first cloud, which by now is turning into a formidable storm. Given that it’s about 80 miles away, I have to drive like billy-ho to get there. As we’re driving, Anton regales Anna and I with stormchasing lore. 

Like all subcultures, stormchasers have their own terminology, legends and heroes. Everyone knows what a tornado is, but how about a dustnado (sort of a dust devil)? Or even better, a sheriffnado (ie a menacing cloud that looks like a tornado, sufficient for a nervous sheriff to call in a tornado report)? There’s the sector of the storm that you DON’T want to be caught in, known as the “bear’s cage”. And there’s the “tailend Charlie” storm, the last storm in a chain of storms, and thus the most likely to spawn a tornado. Ideally, there’s just one storm, sucking ALL the energy from the atmosphere and concentrating it - the more storms there are in a particular area, the more dissipated the energy and the less likely a tornado.

We get to the storm we’re chasing, but a little late. It’s already rained a bit, and it’s getting very windy. The earth is visibly exhaling – white tendrils of cloud literally being sucked from the ground into the roiling clouds above. It starts to rain like hell, the hardest rain you can imagine, and blowing like crazy too. The doppler radar indicates hail very nearby, so we duck into a little housing development and park under a tree. Sure enough - small hail, maybe an inch in diameter, starts whipping violently into the ground, stripping leaves off trees.

As it dissipates, we get back on the road. We pass a field covered with hailstones - 4 inch hailstones, the size of softballs! The radio is blaring the emergency broadcast system - “Tornado warning...Route 14...get out of your vehicle immediately and seek shelter...” (a road sign whizzes past - Route 14!). “Tornado on the ground, town of New Crystal...” (another road sign, “Welcome to New Crystal”!!)

Anton is unfazed - “we need to punch through the core of the storm – we’re on the wrong side, it will all be clear on the other side, that’s the best place to be chasing from”. Well, thanks. Time for another diaper change! We come to New Crystal - trees down all over the place, siding and other building debris in the road. Luckily the cop behind us seems distracted as I weave my way through.

(Anna subsequently admits that when we were sitting under the tree in the hail, she had this epiphany that my brother is, in fact, completely insane, and that her trust in him was utterly and entirely misplaced, and that she was going to perish in that spot, in a housing development a thousand miles from her young family, and ten thousand miles from her home in Johannesburg).

We waited for the storm to get ahead a bit, and then abandoned it. For the rest of the day, and most of the following day (with the formidable Tracie at the wheel – WHAT a driver. And when she’s driving, I get to actually take pictures), we played cat & mouse with a few other storms. We were in better position for these. The idea was to stay just ahead of the storm, and stay parallel with the gust-front, the enormous, maraudering dark billow cloud that advances into the hazy murk, sucking the moisture up and funneling it to the exploding thunderhead. To do this, one blasts along dirt roads (the entire region is neatly gridded into 1 mile squares), zigzagging to stay just ahead. We’d stop on occasion and get out to watch - the insane “whale mouth” skies, the vicious huge mosquitoes attacking, and absolutely constant thunder, a perpetual low rumble (from lightning 7 miles above), punctuated by the sharp explosions of the lethal cloud-to-ground lightning closer by as the storm approached. Further away, the bruised squid-ink indigo near the core of the storm, studded with the strange greenish of hailstorms, and frequently eerily backlit by the yellowish sun on the far side of the storm.

Interestingly enough, of course, we weren’t alone. There were dozens of other people out there doing the same thing as us. In fact, chaser traffic is one of the biggest hazards - as the weather becomes more threatening, the propensity of stormchasers to pay attention to the rules of the road evaporates. So at times we’d be pounding along in a little convoy of six or seven vehicles, and then at the intersection some would go left (into the teeth of the storm), some would go right (running away), and others would go straight ahead (trying to outrace and get into better position - that was usually us). Many of the chasers are networked, so we could actually follow storms by looking at maps showing where the chasers were (of course we didn’t actually do this - why follow the herd?)

At night, we ended up in small towns, eating pretty lousy food. Such fertile land, such huge farms, and not a fresh vegetable in sight? As it turns out, that first storm we’d chased (the big hailer) had gone on into the night, and ended up spawning an F4 tornado in the dark (F5 is the most powerful designation for tornados - an F4 is a very serious and destructive storm indeed). Personally, I’d like to SEE an F4, from a safe distance. Poking around for one in the dark? For the birds! 

Of course, a huge pleasure was the luxury of spending a few intense, concentrated days with one of our oldest friends -  I’ve known Anna since she was a tot. It was surreal and beautiful to be singing Danish pop songs under the crackling South Dakota sky (from an album her folks had - Anna’s mom Marianne is Danish). And that drum solo? Priceless! (The song in question? Alla Tin Gala, by Gasolin’. But no doubt you already guessed...)

Back in NY a week now, and Anton sent an email a couple of days ago:“Conditions are looking perfect for next weekend out in Iowa and Nebraska... it’s late in the season...” I immediately begin a mental check of my calendar...hmmm...maybe I can swing it...