Apr 132011
 

Wednesday, 13 April 2011

 

12z April 13 WRF model surface pressures/winds valid 00z 15 April

12z April 13 WRF model surface pressures/winds valid 00z 15 April


 

It’s been an active April thus far across parts of the Plains and Midwest, and it appears likely that trend will continue tomorrow (Thursday).

A vigorous 500mb shortwave trough will eject into the southern plains on Thursday. As a result, a surface low will develop over central Kansas, with a cold front diving south and east into west central Oklahoma by the early evening hours. A dryline will also mix east to near the I-35 corridor along the Red River and portions of south central Oklahoma. These two boundaries will be focal points for thunderstorm initiation in the late afternoon, as intense dynamic forcing from the upper air trough cools the mid level capping inversion. This will allow for thunderstorms to form, from the Red River northward to central Kansas, along the north-south oriented boundary.

Dewpoints in the upper 50s to mid 60s will spread rapidly northward across central/eastern Oklahoma and even parts of southern Kansas by 00z. Strong, deep layer shear in addition to generally southerly 850mb winds in the 30-40 knot range will contribute to curved hodographs and sufficient low level SRH values supportive of tornadic supercells.

Based on the 12z WRF, hodographs IMO look better for long track, violent tornadoes across the eastern half of Oklahoma as opposed to further north in Kansas. However, I think tornadoes will likely occur in both areas. But Oklahoma may stand a better chance at seeing a long track, violent tornado. Storm motions will be more northerly across eastern Kansas, and hodographs there just don’t look quite as good as in Oklahoma. In addition, I wouldn’t be too excited about storms moving north tomorrow in Kansas, since they’d be moving away from the good moisture and CAPE. Thus, in general, I’d rather be in central/eastern Oklahoma. Finally, the terrain is pretty good north of I-44 and east of I-35, so that would be my general target region for tomorrow.

 

12z April 13 WRF 500mb winds valid 00z 15 April

12z April 13 WRF 500mb winds valid 00z 15 April


 
12z April 13 WRF 850mb winds valid 00z 15 April

12z April 13 WRF 850mb winds valid 00z 15 April


 
12z April 13 WRF model forecasting hogograph for Tulsa, OK valid 00z 15 April.  This a pretty good hodograph that is indicative of strong and potentially long track tornadoes, as long as the storm motion is generally to the northeast or east-northeast.

12z April 13 WRF model forecasting hogograph for Tulsa, OK valid 00z 15 April. This a pretty good hodograph that is indicative of strong and potentially long track tornadoes, as long as the storm motion is generally to the northeast or east-northeast.


 

My greatest concern for this setup is the fact that there will be so much dynamical forcing in the upper levels from not only intense vorticity advection at 500mb, but also from the 250mb curved jet streak. So even with quite warm 850mb temps by midday across central/southern OK (16 to 20C), the forcing will easily cool that. Thus, I’m concerned there will be numerous cells that fire quickly as the all the dynamics move into the KS/OK region. And given CAPE values are only forecast to be in the 1500 to 2000 J/KG range, storms may compete with one another for moisture and/or instability. But I’m not sure, because the shear could make up for the lack of substantial CAPE. We’ll see.

Good luck to anyone chasing out there tomorrow!

- Jim

 

12z April 13 WRF 500mb vorticity valid 00z 15 April

12z April 13 WRF 500mb vorticity valid 00z 15 April

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