Long-track supercells formed across the western Great Plains on Tuesday, May 16th, 2017. Accompanied with these supercells were multiple tornadoes, damaging winds, and giant hail upwards of 4.00″ in diameter. Widespread flash flooding also occurred across the Oklahoma Panhandle and southwestern Kansas.
The morning data analysis, including the 1200z / 7:00am CDT observed weather balloon data, sampled an unstable environment with a strong capping inversion in place. Soundings across the region sampled a low-level jet of 35-45 knots. Strong low-level winds in conjunction with rich moisture was one of many ingredients involved for the formation of severe storms on Tuesday across the western Great Plains.
In addition to strong vertical wind shear, moderate instability above the capped layer was sampled, with Convective Available Potential Energy, or CAPE, around 1,500 J/kg. With hot temperatures in the forecast, it was very likely that the cap would erode in the early afternoon and thus lead to the rapid development of thunderstorms across the western Great Plains.
It is important to remember that CAPE is a potential energy, and is an integral of the maximum amount of buoyancy an air parcel may encounter when it can rise freely (the negative value of CAPE is the convective inhibition; CINH, or cap).
Visible satellite imagery during the latter part of the morning revealed an axis of strong thermal instability nudging its way northward into southwestern Kansas. This was analyzed along the moisture axis accompanied by high theta-E advection ahead of the eastward mixing dryline. Diagnosing the theta-E of air is important in determining the characteristics of thermodynamic instability associated with severe convective storms.
The day started with a target area in the Oklahoma Panhandle, as supercells were expected to form along the dryline. Short term, high-resolution model guidance suggested that supercells would merge together into a forward-propagating line of storms with a few semi-discrete storms along the southern flank.
However, the short term model guidance did not come to fruition; rather, supercells maintained their discrete mode throughout the afternoon and into the evening across western Kansas. This is a classic example as to why it is always important to monitor realtime observations, and utilize model guidance with care the day of a severe weather event.
The tornado potential increased as the cloud base height (lifted condensation level, or LCL) began to lower as storms progressed into an environment with deeper moisture. As we began to track the supercell as it moved towards the town of Beaver, Oklahoma, it was periodically tornado warned given modest mid-level rotation.
The LCL of the storm was rather elevated, and was producing golf ball to tennis ball size hail just west of Beaver, Oklahoma. When bases of thunderstorms are elevated, they do not often produce tornadoes. However, a recent case of a funnel cloud occurring within a high based supercell was in Simla, Colorado, on May 8th, 2017. Heavy rain and minor flash flooding occurred as the supercell progressed to the northeast through the Oklahoma Panhandle and into southwestern Kansas.
Tracking the storm back to the north, we left the town of Beaver, Oklahoma, and traveled north towards Englewood and Minneola, Kansas, along Highway 283. While pulled off of Highway 283 north of Englewood to obtain a better view of the supercell, the LCL had lowered tremendously and became tornado warned again. In addition to a possible tornado, very large hail to the size of baseballs was occurring, along with damaging straight-line winds of 70mph as per storm spotter reports.
Traveling behind the supercell as it moved northeast, we continued to move north towards Minneola, Kansas, and began to drove by hail that had previously fallen out of the hail core. Hailstone size began to increase the closer we got to Minneola, and we observed hail close to tea cup size that had fallen across the southern areas of Minneola.
Continuing north towards the town of Minneola, extensive flooding was occurring due to very heavy rain. The power poles on the east side of Highway 283 were down and/or snapped in half. We thought they were damaged by the rear-flank downdraft, or RFD, but it was later confirmed that an EF-1 tornado crossed the road well before we arrived at the scene of the damage. Strong winds from the RFD also wrapped in behind the tornado, and it eventually lifted five miles southeast of Minneola, Kansas. Video of the damage can be seen here by skipping to the 13:00 minute mark.
After arriving in Minneola, we turned east on Highway 50 towards Bucklin, Kansas, remaining south of the supercell. As we traveled east, a significant lowering of the base occurred and a wall cloud formed. The wall cloud at one point was nearly touching the ground as a strong low-level jet near 40 knots began to move into the area (this was sampled on the velocity data from the Doppler radar in Dodge City, Kansas).
Turning north off of Highway 50/400 from Bucklin, Kansas, rotation began to intensify within the mesocyclone. A funnel cloud began to form and did so rapidly, increasing in size. The large funnel cloud was reported to have touched down by storm spotters that were further west of our location. It was visible for roughly a minute before becoming completely rain wrapped. Thereafter, we were unable to physically see the tornado.
The tornado was confirmed by other storm spotters, and moved off to the northeast over mainly rural areas. How long it was on the ground for has yet to be determined, and the tornado has not been rated due to no damage indicators as it remained over open fields.
Below is a map of the preliminary storm report and weather watch verification, from the Storm Prediction Center, yesterday across the nation. A classic severe weather outbreak unfolded across the central part of the United States on Tuesday, May 16th.
This cyclic supercell continued to move across west-central Kansas into the late evening hours. It ended up producing an intense tornado that had a 15-minute warning lead time, according to the National Weather Service field office in Wichita, Kansas. The tornado impacted parts of Great Bend, Kansas, damaging nine homes and destroying another nine homes. The tornado was rated as an EF-3 with estimated winds of 165mph, and was on the ground for 27 miles. It was 300 yards wide. More information can be found here.
In all, from start to finish, we tracked this tornadic supercell for 147 tangential miles from Beaver, Oklahoma, northeast into Larned, Kansas. A radar compilation of the tornadic supercells yesterday can be seen below. The second supercell in the radar loop that moved into the Oklahoma Panhandle was the storm we tracked (note: you may have to right click the image below and open it up in a new tab for it to animate).