Saturday, June 12, 2010

Four tornadoes, Two Days

Deer Trail, CO

Successful deployment on a tornado that lasted longer than 30 seconds by most of VORTEX2, including the UAVs (Unmanned Aerial Vehicles)! Unfortunately due to, once again, a poor road network, tornado pods were not and could not have been deployed. Two tornadoes formed near the same location, but by the time the meso reached the road it was no longer producing tornadoes. After sunset operations were called off and a few anticyclonic* funnels could be seen between lightning strikes, causing DOW7 and another mobile radar to stop and scan. At one point three funnels could be seen at one time.

Post-tornado meso

Limon/Genoa/Arriba/?, CO

This day was very interesting because we almost ran into two (three?) tornadoes. Initially we moved towards a tornado-warned storm in Denver then turned around and decided to target the southern storm near Limon (where we’d been sitting the past few hours). On radar the storm looked nice with a high-reflectivity core and a hook, then it blew up into an HP (high precipitation) mess. The CSWR pod teams were separated so that 15 and 16 followed DOW7 and 11, 12, and 13 took off on our own down a curvy, narrow, dirt road with two media vehicles following us. As we were moving north we got instructions to turn around and move back south to where the circulation was—we’d overshot it. Unfortunately, turning around meant core punching. Within a few seconds of turning around we were taking baseball-sized hail (2+ inches). Baseball hail is interesting for multiple reasons:

1. Its terminal velocity is pretty freaking fast. Imagine someone dropping a baseball from a two-story building and it’s coming at your head. Ok, now instead of a two-story building, that baseball is being dropped from 10 kilometers up in the atmosphere.
2. Baseball sized hail breaks into smaller pieces upon impact. These “small” pieces are the size of golf balls.
3. The microphysics of getting baseball sized hail also means they are few and far between compared with pea or nickel sized hail. So every now and then you just see a giant piece of ice fall in front of you.
4. It’s ice the size of a baseball. This ice actually melted on the way down from the cloud, which means at some point that piece of ice was much larger than a baseball.

Miraculously, we had no major injuries or vehicle damage. 13 has a nice ring of cracked windshield and 11 has a new large crack. Our already super-cracked windshield on 12 received no damage.

Anyway back to the tornado. At this point we can barely see 100 feet in front of us thanks to this wall of precipitation. I was driving, and in addition to being concerned about the hail, I was concerned that the dirt road we were on was getting a bit ruddy; this would not have been the first time a vehicle got stuck in the mud, but we were expecting the tornado to pop up somewhere nearby this time. In fact, it did just that. 13 was leading the pack and from a few cars following distance behind, I saw them hit the brakes and start backing up. Alex got on the radio and shouted frantically “We have a circulation on the road in front of us, we’re turning around, go north!!!” As we all hurriedly tried to turn around in the baseballs on the dirt/mud road, Josh came onto our frequency to say “Did you deploy pods?” Alex: “No we never made it out of the hail to deploy! We’re moving north, the circulation is on the ground in front of us!” Josh: “Don’t turn around, continue moving south. The circulation should be crossing the road now, it’s not that strong, we’re seeing winds of only 80 to 100 mph.” …………….

To recap this deployment: dirt road, baseball-sized hail, oops the tornado is on the road 50 feet in front of us, it’s ok it’s only 100 mph winds, did you deploy?

I’m sure we have very interesting mesonet data.

Driving into core

So we bailed east through the storm, got ahead, then were sent back west towards more dirt roads. We passed by a deployed DOW6 and went in circles on the dirt road network as our instructions changed to get us closer to the meso. We noticed we were getting dangerously close to the core (again), and received instructions to move back east ahead of it (again). As we were all bailing, a tight circulation appeared off to our right which we reported, then a couple minutes later a less tight circulation appeared immediately to the left of the road. Our initial thought was they were both landspouts** and went about our business. Then we received word from DOW6 that it was definitely a tornado associated with the meso; from about half a kilometer away at their lowest scan they had a very pronounced “doughnut hole” on radar at the location we (and they) were visually seeing the circulation.

To recap this deployment: East, west, east, uh oh core, east, landspouts right next to us?, nope more supercell tornadoes.

*Most tornadoes in the northern hemisphere spin counterclockwise, or cyclonically. An accompanying anticyclonic circulation is not uncommon with a cyclonic mesocyclone.
**Landspouts don’t begin in association with the circulation of the mesocyclone, but develop ground circulation along an area of shear (changing wind direction) which is then stretched by an updraft. Landspouts are still tornadoes (people can get into arguments about this), but not the long-lived, damaging types like those that form from a parent mesocyclone. Landspouts can also evolve into traditional supercell tornadoes; the Jarrell, TX beast began as a landspout event.

No comments:

Post a Comment