The Breakdown:
For the first chase of the year, today’s prospects were too good to pass on! SPC had marked south central KS down across western OK into northeast TX under a moderate risk for severe storms with an unprecedented 15% hatched tornado probability with strong wording mentioning “the only question on potential for a severe thunderstorm/tornado outbreak is the thermodynamic environment”. After a long & bitterly cold winter, this was music to our ears. All eyes were on this system since last weekend, as the GFS had forecasted a strong negatively-tilted trough to collide with dew points well into the mid-50s across the first dry line of the year. At the National Storm Chasers Convention, Howie Bluestein even began his presentation with an enthusiastic outlook declaring the potential for this to be “historic”! Needless to say, our SDS was in full swing!!
Chase Account:
Left Denver at 8 AM with Roger Hill & a couple of his guests on a Silver Lining Local Tour targeting the area along I-40 near the TX/OK border. A quick RUC analysis showed that area would see the best surface convergence along the western fringe of a dry line with a surface low rapidly deepening over southeast CO just ahead of a strong (110 kt/120mph) mid-level jet as the day progressed. Instability fields looked ‘decent’ with MLCAPE around 1,000, but that would quickly improve as the powerful 500mb winds pulled out over the area, further steepening the low-level lapse rates. That, along with strong dynamics (deep layer shear at/above 60 kts) thanks to the powerful trough & strengthening low level jet all supported SPC’s encouraging forecast.
Initially, we debated on southwest KS as the better target since the RUC forecasted a secondary impulse to initiate a separate area of storms--possibly the first surface-based convection of the day--near a Dodge City to Wichita area. With timing such a critical factor we decided to stay the course on our original target & hope for some pre-sunset touchdowns.
As we crossed the dry line near Panhandle, TX, it was fun watching Roger measure the temperature & dew point with his mini-anemometer. Within a 50-mile stretch, the dew point rose from 22F up to 45F & kept rising. Temperatures quickly hit the mid-70s once we reached the northern Panhandle. The surface low had formed over southeast CO and the LLJ was rapidly strengthening! Southeast of Amarillo, we waited most of the early afternoon for the first signs of convection & steady cumulus towers. The first towers were too high-based & sheared over. Scattered raining Cu’s kept building & drifting northeast, shearing out before developing stout updrafts (typical of early season systems that lack the stronger early afternoon instability of main season storms). Clearing skies signaled the deepening instability was building & stronger towers started forming. By 3:00, the heavy cumulus field started to thin out, congealing into larger towers to our west. We stayed on the cells in the development area & watched as they formed clear slots & rained out time & again.
Eventually, the updraft towers of the McLean storm moved into a vorticity rich area that likely had enhanced low-to-ground level shear from the passage of the first cells. We watched from the storm’s west edge as the McLean towers erupted into anvils, an awesome sight as the bases dropped & updraft towers tilted over literally before our eyes --classic tornadic supercell evolution!! Staying on the storm’s western flank, we retraced east on I-40 & spotted a clear slot & developing wall cloud (mesocyclogenesis) just west of McLean with strong cascading motion. A surging downdraft tilted the shear vertically and at 5:50 we had tornado!! The narrow vortex stayed on the ground for about 10 minutes, maintaining classic clear slot/RFD structure throughout its lifespan. It reportedly damaged a farm house & some large farm equipment before thinning out & dissipating a short ways north of us. Another potent supercell just 25 mi. to our southeast also had reports of multiple touchdowns. Unfortunately, as the McLean twister roped out to our north the van’s oil line broke, forcing an abrupt but ‘smooth’ end to our chase day.
We watched the next tornadic supercell from a distance as it put on an impressive lightning show, even spotting a couple cloud-air bolts in the fading daylight. Meanwhile, Roger called AAA. After briefly discussing what went wrong and making a quick post on Stormtrack, we debated possible options & strategies for tomorrow’s cold-core setup in north-central KS when the tow-truck finally arrived. We hitched up & drove back to Amarillo, where Roger picked up a rental SUV. We transfered the equipment to the rental & continued east straight across the Panhandle into western OK, found a small-town motel a little ways west of OKC, and at long last bunked down for a short night.
All in all, today’s chase was a great start to the incredibly early season and just what we needed to shake off our SDS blues!!
