|Friday, 30 July 2010 23:57|
Total Distance: 370 miles
Today was definitely a structure day, that's for sure. Dan Dawson, Howie Bluestein, and I made the trip southwest from OUN with an initial target of between Snyder and Hobart, OK. Upon seeing initiation W of SPS, we hedged a bit south, and sat in Lawton for a half an hour waiting to see any signs of life nearer the warm front. SFc maps at the time showed the low-level moisture mixing out across the DFW metroplex northwestward towards SPS, where Tds generally resided in the 55-59F range. Despite this, the only game in town was the triplet of cores W of SPS, so we darted southward towards Burkburnett.
By the time we made it to just N of SPS, the supercell had already produced all the tornadoes it was going to produce. We did see a nice RFD cut NW of SPS, but the base looked mighty high for most of the time. This storm died a slow death as it moved north of our location (a few mi W of I44 about 10 mi into TX), though we watched with some fascination at the many possible gravity waves produced by the supercell as they spread northward. ~3 were readily apparent from KFDR over the course of 2 hours, with Tcu and Cb developing on each wave as it near Lawton, only for all to fall apart w/in ~30 minutes of going up. FWIW, I believe the storms that developed near and W of OKC after dark can be directly tracked back to one of these waves that originated from the SPS storm sometime near 6p.
At any rate, winds backed to an ESE direction across southwestern Oklahoma (near our original target area), and Tds pooled to the 60-62F range. However, vis sat showed no substantial area of Tcu farther north (confirmed with our eyes, obviously). As convection slowly intensified near Seymour, we were all set to head back northward into OK in hopes that something would develop in the marvelous shear and pooled Tds just south of the warm front across western Oklahoma. Just as we were about to leave, the two cells near Seymour intensified rather quickly. Instead of heading S, we dropped south-southwestward towards the two cells.
We came into view of the 1st supercell (the 2nd of the day, really) WSW of SPS, where some very good structure was evident. An RFD tried to cut into the storm, and a wall cloud developed with pretty good rotation and upward motion. However, a cell to its south was disrupting the inflow to this northern supercell. Given the proximity of the storms, it seemed prudent to drop southward yet again to the "tail end charlie" supercell. So, we dropped south to Windthorst TX, running through 3/4" hail on the way (maybe bigger -- we didn't stop to size it up given that the main core was just about to come over us). The structure of the updraft was incredible at this time (815-830p), with multiple tiers in an upside-down wedding cake fashion. Unfortunately, we were right underneath the updraft, so it wasn't really possible to take pictures (we needed to be 15-20 miles away to get some good structure shots). This cell too slowly weakened as it moved to the E, and we headed back home on I44.
The 00z soundings reveal that, as I had feared (and many others had feared, I should note), moisture was the primary inhibitor for more significant tornadic action. Heck, the MLCAPE at OUN and FWD were both in the 750-800 j/kg range, with 45-50F tds just off the deck. Despite the hope of adequate moisture return last night, it appears that it was insufficient. All the storms looked rather high-based when we saw them, and the 55-58F tds "dry hole" in N TX didn't help any. It's worth noting that the 4km WRF run from last night (forget which particular run -- EMC or NSSL) had big "holes" in the higher Tds across southern OK and northern TX today, with Tds as low as 52F in some areas. I brushed this off last night since it seemed to be ridiculously low. However, looking at obs near 5-6pm, it doesn't appear to have been too far off. The various RUC forecasts (and earlier NAM forecasts) of 65+ Tds in southern OK and northern TX were obviously horrendous.
For all intents and purposes, meager moisture ended up laying waste to an extremely good shear profile across the risk area today. Alas, it is only early April, a time of year in which we expect moisture to be a primary inhibitor. And here I was, thinking that we may actually see a significant tornado day in Oklahoma... Foolish me -- I ended up about 75 miles farther south than I ever thought I'd be today (I didn't think I'd have to go south of LTS-LAW), with no tornadoes. Good structure makes up for it a bit, but I'm chomping at the bit for a good tornado, especially given the hype of the past few chase days.