Today does not look good for Central Oklahoma.
When I’m in a rapid outlook mode, I fall back to several forecast graphics that take into account a bunch of parameters to draw risk areas based on a particular model. It saves time over a detailed analysis of the underlying model parameters, but can lead to a bit higher margin of error. I’ve done both levels of analysis today,but am choosing the set of graphics based on multiple parameters because they most clearly show the risk.
With each, I am showing the output from three models, in the same order: RUC2, NAM and GFS.
The first graphic is for what we call the “Davies number” it factors in the typical strength of the cap based on time of year –by this time of the year there is not much adjustment going on, and the cap is pretty much eroded by 4pm any way. This is a depiction of risk for 8pm CT today, based on the RUC2 model.
Don’t focus on what the various colors mean…just look at the size and location of the darkest red blob.
These graphics are generated by another algorithm developed by Jon Davies, the SSCTOR (Significant SuperCell TORnado).
Note that the models differ a bit in placement, but place the highest risk areas within a reasonable distance of one another, clustered around a point southwest of OKC. Same as above, the raw value of each color is not as important as the relative placement of (especially) the purples.
The last set of graphics is based on the STP (Significant Tornado Parameter), in this case the newest version of the algorithm, recently updated by Rich Thompson at SPC.
This one shows the biggest disagreement between the models, I think. the RUC is holding things back a bit, leaving northern Oklahoma in the highest risk based on this algorithm. The GFS is furthest south, with the NAM shaded a bit south of the mid-point of the other two. Based on performance through this storm system all week, if pressed to follow only one of the models, I’d default to the NAM solution.
But here’s what is jumping out to me: for the first time this week, these three models are in what I would call a consensus. At some points earlier this week the peaks of the parameters have been a state or more apart. Now the spread is less than 150 miles.
Put that together with the analysis I’ve done of the RAP and NAM values for available energy, lift, twist, and what the wind profile is expected to look like in the 4-10pm time frame, and I think the heart of Oklahoma is in for another high-end day. Hereis my highest-risk areaperdiction.
Any storm that can (like the Moore tornado) remain separate from the others will have a good chance of winding up and laying down a strong twister. The negative today is lower wind speeds closer to the ground. But many are calling this an analog to May 20th. I agree.
Here are the money paragraphs from this morning’s SPC outlook:
RAPID THUNDERSTORM DEVELOPMENT EXPECTED BY 21-22Z ALONG OR N OF THE I-44 CORRIDOR...AND W OF I-35 ALONG THE DRYLINE WHERE INTENSE SURFACE HEATING WILL OCCUR. THE STRONG-EXTREME CAPE AND EFFECTIVE BULK SHEAR AOA 50 KT WILL FAVOR THE PRODUCTION VERY LARGE HAIL /BASEBALL OR LARGER/...ESPECIALLY WITH THE MORE DISCRETE STORMS EARLIER IN THE CONVECTIVE EVOLUTION. THE TORNADO THREAT IS A BIT MORE IN QUESTION GIVEN [....] RATHER MODEST LOW-LEVEL FLOW/SHEAR FARTHER SW INTO OK. STILL...AN ISOLATED STRONG TORNADO MAY OCCUR AS THE EXTREME INSTABILITY COMPENSATES TO SOME EXTENT FOR THE WEAKER LOW-LEVEL SHEAR.
Please review these posts to prepare yourself mentally!