Tornado Central

I uploaded some pictures and a brief narrative of the recent ice storm in Oklahoma at http://www.tornadocentral.com/events/icestorm07.php . Alternatively, this page can be accessed by clicking on "Other" on the left, then clicking the appropriate link. Just FYI.

I continue to see mixed freezing rain and sleet. Most of the day, I'd say the predominant precipitation type at my house (on Waterloo E of I35 along the Oklahoma / Logan county border) has been sleet (IP), though we did have heavy enough liquid precip about 30 minutes ago that it started overflowing the gutters (granted, they're clogged with leaves that I haven't had time to remove, but it's interesting nonetheless). I'd say there's ~0.4" of glaze on the grass and branches, but the solid surfaces (i.e. my concrete driveway) has a good deal of sleet on it, so walking isn't too bad (the sleet acts to bite into the glaze ice a bit, giving a little bit of traction).

The Missing or Calm wind obs on the Mesonet can most likely be attributed to frozen anemometers. I just took a stroll down the road, and I'd say sustained winds are 5-10 mph.

I'm quite fascinated by the persistance of the quasi-stationary band of precip that started about 24 hours ago along I44. Asphalt roads are still largely just wet, not surprising given 2" and 4" bare soil temps in the 34-36F range (see http://agweather.mesonet.org/soil/default.html ). The freezing of the roads will be slowed a bit as the freezing process itself, as I'm sure we all know, releases energy (i.e. latent heat of fusion slows the freezing process). I'm still looking to get out tomorrow morning to take some pictures. Some of my favorite winter landscape pics involve glaze ice.

FWIW, news is reporting 100 auto crashed since last night, with 8 fatalities (a count that doesn't include a multi-fatality collision in Okemah along I40 that closed that interstate). Enhanced rainrates expected given possibility of convection yet again tonight. The 00z OUN sounding (http://www.spc.noaa.gov/exper/soundings/07121000_OBS/OUN.gif ) showed ~700 j/kg MUCAPE, with a very impressive warm nose (~10 C at 850mb... in December!). Interestingly, there's also ~45-50 kts of effective shear (~35kts at updraft base / 850mb / increasing to 85kts at the equilibrium level / ~300mb) which may promote a little organization to some of the storms.

KTLX base velocity data at 0300 UTC indicate that the cold air is back down to near 2800-2900 feet in depth. If I recall correctly, the cold air deepened earlier this morning to near 4000 feet, so it's decreased in time lately. This is not surprising given the strength of warm air advection just above the cold dome. Eventually (most likely by tomorrow afternoon), the freezing line should move back northward. Of course, it's important to note that models have a strong tendency to underforecast the speed and intensity of these shallow arctic air intrusions, so I wouldn't be surprised to see subfreezing temps hold on a little longer than models forecast.

I'm always fascinated to see moderate convection when surface temperatures are below freezing. A look at the Spencer, OK, mesonet meteogram (Spencer is just northeast of OKC), shows that it picked up 0.5" of rainfall in a 20 minutes time span near 1am. The temperature at the time was around 30F, and the temp has continue to fall to a current value of 28F. Not surprisingly, the anemometer appears to have been frozen, given that it's currently not reporting any winds. For ASOS/AWOS and mesonet sites, calm or missing winds are usually good ways to find where the precip has been falling as freezing rain (assuming ambient/environmental winds are >3 mph). A glance at surface obs on the OK mesonet show about half a dozen sites with missing winds (at a time when most wind obs in central and northern OK are 10-15 mph sustained).

FWIW, temperatures have also fallen into the teens in far northwestern OK, with 8-15 mph NNW winds likely continuing to bring in low-mid 20F temps closer to I40. These very shallow arctic fronts have a tendency to be underforecast by most models (both in intensity and speed), so this isn't too surprising.

07 UTC SPC/RUC mesoanalysis also continues to indicate >500 j/kg MUCAPE, supportive of a continued risk of thunderstorms and upright convection. The band of heaviest precip just N of I44 east of I35 in northeastern OK appears to be in an area of decent frontogenetical forcing (and the fun ageostrophic accelerations associated with such forcing). The 850mb cold front may be a good marker for the freezing rain - snow transition zone (or liquid - frozen transition zone).

The VWP from KTLX valid 0720 UTC suggests that the top of the cold layer is ~1800 ft AGL (I'm using the 2.5 degree base velocity data to pick that out easily; KINX / Tulsa / data suggests a similar depth). The cold air deepens to >3000 ft above the KVNX radar, pretty much in line with velocity data from KICT. Given this, I wouldn't be surprised to see some sleet mix in with the freezing rain closer to the OK/KS border west of I35. Well, maybe not, but perhaps close... Same mesoanalysis shows the 850mb front located near a line from Shamrock TX to Emporia KS to the NE MO / SE IA border area.

EDIT: It's important to note that, per OK Mesonet (see HERE), current 2-in and 4-in bare soil temperatures are in the mid 30s in most of northern OK. As such, the precip is not likely to freeze upon impact of roads. Elevated surfaces that tend to cool to ambient temperature more quickly (e.g. powerlines, trees, bridges) are likely icing up rather rapidly right now N of I44. I imagine that it may take until tomorrow night for most areas to see ground temperatures (at least 2" or 4" below bare soil) reach the freezing mark.

EDIT 2: OGE System watch (HERE) is showing >1000 customers w/o power in eastern OKC. Of course, in the scope of things, this isn't a large number. However, I think this is only a hint of what's likely to occur in N of Tulsa through the morning. Latest TLX data shows convection and showers are redeveloping in the quasi-stationary zone along I44, from near Chickashaw to Norman to Stroud and Bristow. My house in Arcadia is currently between this band to the south and the intermittent activity nearer Perry and Guthrie. *shrug*

Dan Dawson, Gabe Garfield, Nick Bierman, my wife, and I chased the tornadic supercell NNW of Fairview OK this afternoon and evening. Though our expectations were relatively limited, it ended up being an awesome chase. The motions at cloud base (both in the horizontal and vertical) were quite impressive. The first attempt we saw at tornadogenesis occurred just N of Hwy 412 W of Orienta late afternoon, with a decent funnel that excellent wall-cloud. A new storm developed to the south of that first cell, which promptly "killed" that first one. Fortunately, the second cell rapidly developed a wall-cloud, with excellent cloudbase motions again. At this time we noted 1.5" hail on the ground about 2 mi SSW of Orienta. A nice wallcloud developed, with funnel and all. Despite looking like an imminent tornado, it quickly occluded. So, we hopped back to 412, and made it a couple of miles W of Orienta before tornado-mania began. Over the next 10- 15 minutes (guessing -- haven't looked at tape yet), we observed at least 4 tornadoes. Most were relatively small and short-lived, but there was a "fat stovepipe" (tornado #3 I think). All tornadoes were from the same mesocyclone, but they were certainly different funnels and from different areas of "enhanced" rotation. Interestingly, before the last tornado from this sequence, I noted a very rapid sinking motion filled with "ribbons" of precip, something that looked an awful amount like a DRC. The tornado that followed seemed to be the longest-lasting, but it also became enshrouded in heavy precip, which completely obscured it for a while. That tornado looked to move southward too.

After that sequence, we meandered back southward to see what would happen with the next storm the was developing farther south. Supercell structure improved at this time, with nice curved bands feeding into the updraft/meso. Despite wanting to play the tail-end charlie farther south, we opted to stick with this one since it had pretty good structure and it was relatively mature. Given a very slow northwestward motion, we headed back north to 412, before working west into the Glass Mtns. We found a small area in which we could view the meso, and it was at this time that we saw tornado #5 to our SSW. It quickly became a lost cause as extremely heavy precip completely obscured the meso. With the supercell appearing to be a lost cause owing to a very HP nature at this time, we decided to hop southward to see what was next. Well, we didn't really get anything else meaningful, despite fears of very strong winds and large hail as we drove by Canton.

Overall, there is very little to be disappointed about with this chase! Our expectations were low, which may have helped, but I'd still consider this a great chase. And heck, it was even in Oklahoma! Despite 20-25kts at 500mb and 250mb (per 00z NAM initialization), strong instability, good moisture, good directional shear, and an old outflow boundary made for an excellent supercell that was essentially stationary for quite some time. In addition, it was great to FINALLY get my wife on a "good" chase (I like split infinitives).

I'll add pics and video stills this weekend.

Been busy with some marginal chasing since mid-May, as we've had both radars in town since early May. I've added a bunch of pictures to various chases I've been on this year, most notably from 4-23-2007, on which I saw at least 7 tornadoes over the course of about 45 minutes. I've been able to add pictures from several other chases before mid-May as well, all of which can be seen on the 2007 Chase Logs page. I still have a few more chases worth of pictures to upload, but at least most of the logs are current.

Speaking of the radars, we were able to use two mobile Doppler radar this year -- the dual-polarized, X-band radar built by UMass, and a new X-band mobile phased array radar (MWR-05XP) developed largely by ProSensing, Inc. Below is a picture of the two radars in operation (from a late May chase in the TX panhandle):
** CLICK ANY PICTURE BELOW TO SEE A LARGER IMAGE **



One interesting event that occurred while I was out of town -- we apparently lost a tree near the side of our house to a lightning strike! It missed the corner of the roof by about 10 feet, so it was a fortunate miss. The "branch" was the lowest to the ground, and it was one of the largest on the tree. The "rip" in the trip is about 8 feet long, so, given it's location near the ground, I'm not sure if the tree is going to survive. I've been able to chop up most of the branch, but a 20 foot section nearest to the trunk of the tree is still attached. Below are a few pics of the tree:




KFOR (Channel 4) in OKC did a little story on our research group a few weeks back as well. My time on camera isn't much (they cut my answer to one of the reporter's questions), but Robin and Howie (obviously) get some time. Click here --> KFOR Story <-- to read the story. Click the video icon beneath the title of the article to view the video.

On a non-weather note, I posted a bunch of pictures from Lauren and Billy's wedding in early May. See here --> Lauren and Billy's Wedding <-- for pictures.

Oh yeah, before I finish up... I'll update the Pets webpage sometime in the next week. We have finished our animal expansion, as we're at max capacity when it comes to pets. Windy, Hailey, Rainy, Vorty, Doppler, Squirt, and Madison -- two rabbits, one hedgehog, one guinea pig, one dog, and two cats. Whew. The new kitten stands about 7 inches tall; he's a tiny little guy!

No time to post much in the way of updates lately. I think the only significant event that happened since the last post was a crazy tornado-fest on 4-23 in southwestern Kansas. We saw ~7 tornadoes in the span of about 45-60 minutes, including one time during which there were 3 tornadoes on the ground concurrently. I've certainly never seen that before!

Tomorrow looks like a potentially excellent chase day in Kansas. I'm concerned about initiation and the location of dryline / triple point by late afternoon. The NCEP models have been quite underwhelming in terms of accurate dryline position (even the 12hr forecasts -- see 3-28-07), so I'm not sure what to think. Forecast hodographs display an excellent shear profile by 0z ahead of a dryline bulge in western Kansas.

Kim and I are leaving for Lauren's wedding Florida sometime early-to-mid morning on Saturday. As such, I'm not too keen on driving N of I70 tomorrow, since that'll likely mean an arrival back in OKC-area around 3-4am... If we leave ~8am Saturday, that doesn't leave much in the way of sleep.

Speaking of Saturday... Looking at the 18z GFS and NAM, it looks like Saturday could see the best potential for a violent tornado outbreak that the Plains has seen in at least 3 years. The last time I saw a setup this favorable was 5-29-04, and that day was a little disappointing in terms of storm coverage (unless you were on the supercell in southcentral KS, in which case it didn't matter ;) ). Otherwise, I need to go back to the May 4-May 8 2003 time period to find a chase setup that resembles, in terms of areal extend and intensity of potentially-tornadic supercells, what we should see Saturday. Alas, I knew months ago that the only time during which I cannot chase this spring (May 5-8) would turn out to be a major outbreak time. Oh well -- I can't complain too much given how good of a season I've had so far this year. And hey, a lot can change in 48 hours. I wouldn't be surprised, however, to see a High Risk on the Day 2 outlook tomorrow.

Looks like there's a pretty good possibility of at least one chase in the Fri-Sun time period, but I refrain from getting too optimistic until we get a better idea of the amount and depth of quality moisture that will be in place ahead of the dryline. The Gulf has been obliterated in the past week, so I'll remain on the pessimistic side until we see >65F Tds streaming past Austin and Houston.

As mentioned in a previous blog entry, Kim picked up a hedgehog from a fellow vet-schooler this past weekend. She took a picture of him yesterday:




Also, we fell for a mild-mannered, smart golden retriever "pup" this afternoon from the Guthrie animal shelter. Rainy (or Rainey -- I don't have the spelled decided upon yet) now makes the 6th pet in our household (an addition to the hedgehog, two rabbits, guinea pig, and cat). We don't have a fence yet, but she is remarkably calm, so that shouldn't be of pressing importance. We started crate training this evening, but, admittently, this will be somewhat limited until we can get her into a larger crate/kennel.



I'm running a little short on weather-related pet names. So far, we have Windy, Hailey, Vorty, and Rainy. Any ideas? Stormy, misty, gale, stratus/strato, nimby/nimbus, Rossby, ... ?

A disappointing chase through northern Texas yesterday, though there was the potential for a much more severe (and tornadic) event. I just posted my chase log and map, which can be read on the 13 April 2007 Chase Log page.

Next chase day appears as though it won't be for at least 4-5 days, as a strong cold front is currently blasting through the Gulf of Mexico, which will significantly delay strong moisture return into the Plains. This is actually fine with me, since I have quite a bit of school work and thesis work to get done in the next week or two. That said, I'm never upset to have the opportunity to chase!

Oh yeah, we picked up another exotic pet today (our two rabbits are technically considered to be exotic pets) -- Vortie, the hedgehog. Yeah, vortie is an odd name (and a hedgehog is an odd pet!), but it's weather-related and not one that I want to save for a dog. Vortie joins Hailey, Windy, Madison, and Squirt as household pets. You can probably guess pretty easily which ones I named.

Those would be Vortie, Hailey, and Windy, obviously. ;)