May 16, 2017

Team Turtle (Skip and Jenn) Forecast:

“Tomorrow looks like a classic. I'll keep this short and sweet as it's late and folks are travelling. NAM and HRRR are in good agreement, couple things jumping out at me.

A moisture plume tracking north across the TX PH into KS. It coincides nicely with the trough nosing in from the west. Speed max lags to the west, but 50-60 knots of bulk shear across a strongly unstable dryline looks great.

Both models are in agreement of a morning MCS kicking off in the ne TX PH and tracking into KS leaving a cold pool in its wake. Might throw a wrench in the setup, but it's also maxing out the tornado parameters following recovery, keeping surface winds backed, and the LLJ is ramping up early on. SRH is quite high by 21z even, and despite the cooler temps, moderate surface based instability persists. Big curving hodos, large instability, low LCLs for mid afternoon... would not be surprised to see significant or even a violent tornado tomorrow.

LSIs are opening by 21z, and high-res models are in agreement of a 20z-21 initiation on the dryline across the TX PH into KS. The cold pool may delay initiation in the ne TX PH corner, but storms interacting with an outflow boundary or tracking into this environment as it recovers may be the main tornado play.

Would target Booker, TX for early evening tornado play. Points west-southwest for initiation. HRRR is slightly west with the dryline than NAM NEST with storms possibly initiating by Dumas and points north and south from there. We' are considering a route for Perryton, TX and would try to be there well before 20z and adjust as needed. Main concern would be the cool pool splitting the target and forcing a race north to Dodge City or down south of 40 if that ne TX PH is shut down.”

Team Duck (John and Rose) Forecast:

“Well it’s certainly an interesting morning forecast (wish I had to say that last year).

A surface lee low INVOC central CO has formed in response to the approach of a very strong upper shortwave trough, with the SW component leading to sharpening of the dryline over the NM/TX panhandle border. Large scale moisture transport will occur during the course of the day associated with mass response and the development of a pronounced LLJ ahead of the dryline by 21-00UTC (50 knots – so you can imagine what that does to a hodograph). Cloudiness will result underneath the strong capping inversion (8.5-9 C/km Lapse rates – so no punching hail cores today folks – there will be extreme hail) ahead of the dryline, with transport likely to yield mid-60s dewpoints (which seem realistic given the morning surface analysis and rich moisture available in Southern TX and consensus between MPAS, HRRR, HRRR-E (better mixing), NAM). This combination acts in our favor, as it will suppress diurnal heating east of the dryline and lead to an impressive heating differential leading to the eastward dryline surge. The overall shear profiles as Skip suggests remain favorable – with impressive 0-3km SRH from DDC south into the panhandle by 22UTC (see below) – a hazard on this is that MPAS has been overly fast and eastwardly displaced so far this season – so my general feeling is further west (models tend to move drylines too far east due to aggressive PBL mixing parameterizations) – nonetheless, there is a potent environment favorable for supercells and tornadoes given the ~1km AGL LCLs and extremely favorable shear environment, particularly with the increasingly potent hodograph.

No convective signals on radar so far this morning, but GOES-16 should reveal if anything interesting is about – if and where that boundary develops could be very interesting. SPC is going for a 10% hatched TOR region INVOC this intersection of the shortwave ejection, moisture advection and sharpening of a dryline bulge to the SW. Initiation in HRRR is ~18-19UTC, but HRRR tends to get overexcited about ~1 hour-1.5 hours early in most strongly forced scenarios. Nonetheless, I would expect initiation early ~20-21UTC, with a favorable tornado play into the early evening hours as supercells mature. I’m happy to go with Booker/Perryton, TX as an initial target, and revise later on if development in the surface obs. points to a need to do so. “

Another year had passed and we finally had the band back together for our second season of tornado field research led by Anton Seimon and John Allen. Brindley and I left the night before, our first chase of the season together, and were first on the scene at our rendezvous point: a dingy truck stop in northwestern Oklahoma. Things were looking much more promising than last season with prominent tornado forecasts right out of the gate. Tornadoes seemed likely so it was only up to us screw the chase up. The teams converged and we caravanned into the Texas Panhandle to intercept some severe warned supercells that were coming off the top of the Caprock.

Our supercell target ran afoul. Perhaps there was interference with adjacent cells or they were being choked by activity to the south, which was producing a photogenic tornado near McLean, Texas. We had picked the wrong target and were missing the show on our first day out. We were left with a decaying whale’s mouth on our first storm that we tracked into the Oklahoma Panhandle.

We tracked new targets into Kansas, but they seemed to be tracking in the outflow and cold pools of gusted out storms so we initially thought they may have been elevated. Approaching Bucklin, however, a storm shed its gust front and reorganized. A brilliant white rear flank downdraft clear slot emerged to the north. John called over the radio that he had spotted a funnel in the distance and we could see prominent upward motion to the scud. The storm went tornado warned and we felt that we finally had a real chance at catching a tornado.

I took a chance leading the teams onto an unpaved road as we tracked the north moving storm. The gravel soon degraded and we started to slide. Feeling the car start to drift toward big muddy ditches and open water is terror inducing, white knuckle driving. I was hoping the all-wheel drive on my new Forester would give me better traction than the old minivan, but the stock Dueler tires it had been equipped with weren’t very good. I turned us around to get back to pavement and we spent the rest of the chase playing catch-up with the fast moving storm. It apparently produced a large tornado near where we ended the chase in Great Bend, but it was thoroughly rain wrapped. Anton and I made a vain effort to intercept, but we couldn’t see anything as we trailed behind from the south. We turned around and bedded down in Great Bend for the night.

Team Duck Summary:

“An approaching western trough resulted in the eastward surge of a sharp dryline into the eastern TX and western OK panhandles. A rich airmass of dewpoints in the mid to high 60s contrasted dewpoints west of the dryline in the 30s. With the approaching upper trough, significant 0-6km shear of 50-60kts overspread the warm sector, with favourable profiles for the development of supercells. We rendezvous’d just outside of a giant tipi to confer over the day’s target.

Initial initiation began near the effective triple point between a boundary and the dryline in the central OK panhandle. Several storms developed rather rapidly, with weak early tornadoes. From our position in Shattuck OK, we elected to pursue northwestward rather than wait for potentially more messy initiation to our south. Heading west toward Booker TX, there was impressive northward transport and inflow into the southern most storm, which was tornado warned. We moved into position ahead of this storm northeast of Beaver. Undergoing a relatively rapid cycle and a complex multi-supercell interaction, lead to consolidation to our north into a tornado warned storm that was tracking north to northnortheast.

Repositioning eastwards and the north, we caught up with the storm north of Greensburg KS and attempted an intercept of the HP structure which had just occluded. Continuing northward toward Kinsley, the storm began to rapidly accelerate northward with the LLJ to the west of Great Bend, at which time it was maintaining an impressive doppler velocity couplet. This, we would later discover, had produced an EF3 tornado, however it was of very low contrast and rain-wrapped, with very poor road network accessibility. With fading light and storms congealing into a nocturnal MCS with another round to our southwest, we retired for the night in the town of Greensburg.”