Based on veloctiy data from The University of Oklahoma’s RaXpol data (Rapid-scan X-band Polarimetric Radar) the El Reno tornado that hit central Oklahoma Friday (May 31, 2013) has been upgraded to an EF5 tornado, with a maximum width of 2.6 miles. This makes it the widest tornado on record in the United States.And it looks like it was headed almost straight towards my friend John's house, before giving up. Luck held!
Actually I'm a bit puzzled by this. While there was serious damage south of El Reno, calling it a 2.6 mile wide path seems questionable. There may have been a general cyclonic system dropping funnels of varying intensities but there is no indication on the ground of a wide swath of damage. I did not see the area near El Reno but the damage in the OKC area was sporadic. Along NW 10th in NW OKC there was a 3/4 mile section of large power poles blown down but almost no visible damage to structures. My interpretation would be that winds in the F2 range remained at around 15+ meters above ground level.
ReplyDeleteThe Moore tornado, on the other hand, cut a path of total devastation around 1/4 mile wide. A friend stopped by the shop a few days later and I said, "I'm glad to see you survived the tornado.' He responded, "Well, I didn't--I no longer have a house or a car or a bike." Just today I talked to another guy who had lost his house and all other belongings. But things are working out. Insurance is covering most of the losses and emergency workers and volunteers gave help where needed. Things like this are an occasional way of life here.
The disturbing thing about the El Reno tornado was that people were unsure what to do and many people got into their cars in an effort to escape the path of the storm. Unfortunately, there was no clear path and many people drove directly into danger. With normal rush hour traffic and the usual interstate traffic OKC can count itself very lucky that the track did not cause hundreds of casualties on the highways.
Another disturbing aspect was the warning that people "will not survive if you are not below ground". This caused panic among some who did not have ready access to storm shelters and they ducked under bridges where massive stream flow from record rains caused a number of drownings.
And, of course, the mob of perhaps over 100 storm chasers--some working for television stations and others just thrill seekers--accounted for at least four of the fatalities. The guys from the weather Channel got lucky--an SUV that went airborne and landed 200 yards from where they left the road. But the three former WC contractors who were killed were in a Chevy Cobalt (AKA KIA)which is not a vehicle I would want to use under such conditions. The tornado took them all off guard; randomly forming funnels sprang up without warning. A friend of mine who is an experienced meteorologist with a local network affiliate nearly got caught by one. Hopefully these two tornadoes will be a learning experience for everyone in OKC, storm chasers and regular people alike.
-John
Hi John: The pictures of the El Reno storm look ambiguous: like the entire wall cloud descended to Earth. Maybe that's what it was: not a single twister, but the entire mesocyclone, with little twisters circling within about a common center. Big twisters often feature circulations within. Maybe there is no sharp distinction between a big twister and a descended mesocyclone. I've been looking at the soundings for the time of day. So far, they look like you'd expect: lots of CAPE. I wondered about tornado physics. I'm thinking funnels are usually cone-shaped because vorticity is usually distributed vertically in a uniform way, so conservation dictates that the funnel has to be smaller where the air is thicker. So, does the lack of funnel here mean there was a vertical vorticity gradient, with higher vorticity near the surface? I was thinking the sounding might reveal more, but no luck so far. Details of tornado physics are outside my usual purview, but maybe it's worth studying. Do I have a book? Must check!
ReplyDelete