Thursday 18 May 2017

Day 5 - NW OK

The SPC (Storm Prediction Center) had issued a rare 'High risk' of severe thunderstorms for today, capable of all hazards - very large hail, damaging winds and strong tornadoes. I'm always sceptical about Moderate or High risk days because several times in the past these types of days are often associated with ample amounts of the key ingredients required that it tends to turn quite messy fairly quickly, and often ends with disappointment.

With that in mind, there were also large discrepancies amongst the model output as to how the day would evolve, with several of them simulating a large round of thunderstorms moving NNE-wards across Oklahoma into Kansas, which would potentially overturn the atmosphere and make it hard for any significant tornadoes to form with any deep convection later in the day.

In either case, we left Enid (OK) at lunchtime and headed some ways west to get closer to the dryline, which was close to the TX/OK border. Refuelling in Seiling (OK), storms were beginning to fire to our west and becoming quickly severe-warned. We nudged back to Bouse Junction (OK) to give us some options to either of these storms, then up to Waynoka (OK) to wait for the storm near Seiling to get closer - it had become tornado warned, with reports of a tornado on it.

The terrain around this part of Oklahoma is not particularly ideal, with hills around the river valleys and quite a few trees too - it made getting a good visual on the base of this approaching supercell quite hard, especially considering the very low base to the evident wall cloud. As such, we followed the storm for some time north to Alva (OK), but couldn't tell for sure if there was a tornado on the ground or not because of the wide wall cloud that was hovering just above ground level. Nonetheless, it looked very dramatic, but soon began to weaken, so we ditched this storm once we reached Alva and headed back south to chase a couple of other cells approaching from the southwest.

Wall cloud near Waynoka (OK)
These looked like they were weakening as they ran into the much cooler boundary layer air (temperature had dropped from 28C to 19C after the first round of storms) so we were going to park up and let them come over us (as they were no longer with a warning). However, they rapidly intensified as they approached us, and we had to move quickly to keep ahead of them - radar velocities suggested damaging winds of 70+mph were possible. The storm kept accelerating NE-wards and we couldn't keep ahead of it (due to road options) so we had to seek shelter in a car wash in Alva against the large hail. As we parked up, the storm became tornado warned! Numerous emergency vehicles suddenly started their sirens, and the tornado siren then followed - very eerie.

Shelf cloud of approaching storm south of Alva (OK)

Shelf cloud of approaching storm south of Alva (OK)
Our GPS location (blue circle) in relation to the tornado warning (red polygon) at Alva. Any potential tornado would be with the bowing/hook segment to our SE

Radar scans would suggest the part of the storm with the potential tornado would stay south of town so I wasn't overly concerned, but we experienced a lot of heavy rain, thunder and lightning, and a flash flood on the nearby road. Once things had died down, we headed south and spent the night in Elk City (OK) to get closer for Friday's target - the town who's southern suburbs were hit by a substantial tornado on Tuesday.

Day 5 GPS tracker

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