May 2, 2018: Another Round of Severe Weather in the Central Plains

May 2, 2018: Another Round of Severe Weather in the Central Plains

Update: 9:00 PM CDT May 2

While it looks like things have not been too bad in the Oklahoma City area, there have been a few tornado warnings. The most interesting looking storm at the moment is what could be a possible tornado embedded in a line of thunderstorms that just passed through the northeast side of Norman, Oklahoma. Radar showed rotational velocity of about 30 knots, which while not terribly strong, was at an altitude of only 300 feet. Furthermore, quasi-linear convective system (QLCS) tornadoes tend to be associated with slightly weaker rotational velocities than supercell tornadoes (which typically have rotational velocities of 40 knots or higher). There have not been any tornado reports yet, but any tornado embedded in this line was likely moving very fast, wrapped in rain, after dark, and was passing through very hilly, forested terrain. While storms seem to have grown upscale into a line, and we will primarily see a damaging wind and heavy rain threat going forward, given the strong wind shear, do not be surprised if we see some more of these spin-ups heading into the late evening. This threat also extends up into Kansas and Missouri. Another one of these spin-ups appears to be underway on the far south side of the Kansas City Metropolitan Area along the Johnson-Miami county line.

0.5 degree reflectivity (left) and storm-relative velocity (right) showing a possible tornado northeast of Norman, OK at 8:46 PM CDT May 2, 2018. Radar image produced using GR2Analyst.


Reflectivity (left) and velocity (right) radar data of a possible QLCS tornado south of Kansas City at 9:01 PM CDT May 2, 2018. (Image source: GR2Analyst).

Update: 6:30 PM CDT May 2

Forgot to mention in the previous update, but the environment remains extremely favorable for severe weather. Surface analysis reveals temperatures in the upper 70s and dewpoints in the upper 60s to near 70 across central Oklahoma. SPC Mesoanalysis shows CAPE in excess of 3,000 J/kg, but also some convective inhibition remains. The convective inhibition could inhibit the tornado potential somewhat, but basically every other parameter is excellent for tornadoes (the Significant Tornado Parameter is in excess of 7.0!).

Radar and surface plots from Digital Atmosphere Workstation.
Significant Tornado Parameter (STP) and radar from SPC Mesoanalysis.

Update: 6:15 PM CDT May 2

The storm of the day so far appears to be a supercell thunderstorm that formed over southwest Oklahoma and has tracked northeast and is now near the town of Binger, Oklahoma (about 50 miles southwest of Oklahoma City). There were a few brief tornadoes earlier, but no tornadoes have been reported for some time. Still, the storm is very strong. The image below is a cross-section of radar reflectivity of this supercell. Note the very high reflectivity aloft above the clear area. This clear area is rain-free base or inflow part of the storm. The high reflectivity aloft is the overhang and is the result of rain and probably some hail being suspended well above the ground from the strong updraft. We will have to keep an eye on this storm as it tracks towards the Oklahoma City Metropolitan Area.

Radar reflectivity cross-section of supercell thunderstorm near Binger, Oklahoma at 2259 UTC (5:59 PM CDT) May 2, 2018 from the Oklahoma City (KTLX) radar. Image created with GR2Analyst.

Original Post

A second day of severe weather is underway today across the Central Plains. As of this writing, there are two Tornado Watches in effect in Kansas, Oklahoma, and Texas; and an additional Severe Thunderstorm Watch in Illinois. The greatest threat will be within the Tornado Watches, but especially in the Kansas watch. SPC has a moderate risk in this area for damaging wind gusts.

SPC Watches valid 4;31 PM CDT Wednesday, May 2, 2018.

Surface analysis in Kansas reveals a cold front from Falls City, NE to Salina, KS to Perryton, TX. Thunderstorms are already ongoing along this cold front. Ahead of the front, temperatures are in the lower 80s with dewpoints in the upper 60s across eastern Kansas. Given the very steep lapse rates, the atmosphere ahead of the cold front is very unstable.

Surface analysis valid 4:30 PM CDT Wednesday, May 2, 2018.

Several severe thunderstorm and tornado warnings are in effect for portions of this line of thunderstorms. While low-level shear is strong and a few tornadoes are expected (and in fact, have already been reported), the linear storm mode and very large downdraft CAPE suggest a primarily damaging wind threat as storms push east towards the Kansas City Metropolitan Area late this evening, though a few embedded tornadoes will be possible as well.

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