EWP Blog

Went with another TOR for Brule County. The storm turned right and the low level circ increased/tightened up. Also saw an increased updraft (around 15 ms^-1) and increase in updraft helicity.

We have warnings out on a few storms to the SW of Midland.  Storms have increased SW of Midland past couple of hours and this is semi-inline with the OUNWRF forecast of increasing tstm coverage over the central and eastern zones through the course of the evening hours. The model has been consistently too robust on the coverage of storms and too east with the timing of storm placement.

Latest model run still shows some strong Surface Max Hourly Wind Speeds near 30 m/s in the first 1 to 2 hours but then indicates a broad weakened wind field around 20 m/s or less in the 3 to 6 hour forecast.  Radar data suggests main threat with these storms would be large hail, and the OUNWRF has Max Hourly Column Hail around 64 kg/m3 just east of where the storms currently are in the next hour…which is verifying fairly close to current radar observations…just a bit too far to the east.   Most WRF parms seems to be indicating a potential for stronger storms through 9 PM then a weaker trend with tstm intensities by 11 PM as the storms move east into the eastern zones.

Tim/JeffG

Looks like the MESH has been a little low today at least with the Beadle County storm. Been getting golf ball reports although the MESH max has been 1.8 inches. In fact, got a report of golf balls near Broadland at 725pm, but only got a 1.2 inch MESH. Interestingly, the old school Hail Algorithm from the 88D suggested 1.75 at this time.

This storm took it’s time developing but maintained a persistent circulation throughout Brule County. Opted to go with a TOR based on the persistence and depth of the circulation combined with the az shear product. 3dvar also showed an increasing updraft. Storm is very far from the RDA, so there are some velocity quality concerns.

Switching WFOs was the trick. A pair of supercells over north Dallas were just putting out large hail about the time we swtiched. 15Z SREF composite indicators such as Prob of STP > 1 and SCP > 3 have bullseyed this area around 00Z, nice verification.

MRMS MESH shows a nice hail core in the eastern storm. Numerous reports of hail to tennis ball size have been received. The western storm, in spite of MESH values < 1.25″, had a report of golf ball size hail in Grapevine.

3DVAR has good updrafts (~13 m/s) and even better upper level divergence (11 s-1). Not seeing much in the wind or helicity fields yet.  88D velocity from KFWS not showing well defined mesocyclones as of yet. Though we did see a really pronounced 3-body scatter spike.

SNELSON/TY

Switched domains to the FWD CWA. Ongoing supercell were producing hail over 2″ inches in diameter across eastern Dallas county. KFWS radar showing new supercell developing over the western portion of the county. Cloud top cooling product showed tops of >-21 degrees Celsius. Issued a severe thunderstorm warning based off both 88D reflectivity and cloud top cooling. Have since got reports of ping pong ball size hail.

KFWS radar at 2335z (warning issued on both storms):

Cloud top cooling product about 30 minutes before:

Update 0014z: MESH has shown hail sizes around 1.5″. Most real-time hail reports have been ping pong size. Solid.

Update 0052z: The western Dallas county supercell has mirrored the earlier storm to the east, based off of reflectivity. Hail up to 3″ in diameter has been reported with the storm which is double what the MESH was suggesting. At the same time of the 3″ report near Grand Prairie, divergence aloft increased to 10.7 s-1 with an updraft helicity of 145 m/s2.

Great left mover — developed a strong anticylonic circulation with depth. Went with a tornado warning based on the strong gate-gate shear of about 40 kt. We will see…

CTC on the Lyman/Buffalo County Storm peaked at around -21C/15min at 2145z. Just got a severe report at around 2247 of 1.75 inch hail with the storm in Lynam County so it looks like about a big hit for CTC. MRD/RS

Updraft in north central Colfax county may actually push the severe limits. 40 dbz is reaching higher into the cloud (we are reaching here). The visible cloud presentation has become more intriguing. Lightning has also been detected with this thunderstorms for the first time today.

Cloud top cooling product has shown -11 degrees C, well below our severe threshold, but it is a start.. However, MESH is still underwhelming despite the slight increase. We are still not confident in much activity making off the higher elevations, and the latest run of the OUN WRF continues to support our forecast.

Cloud-top cooling product:

MESH at the same time (look closely, it;s there):

It’s getting bigger. MESH at 2214z is now up to 0.40″.

and as I write this, the temporary strengthening ceased. Now onto storms in the southern ABQ CWA.

We abandoned ship and moved way north to look at the development in SD. Good looking cell moving into Bruce County however the MESH is only up to 0.79. Will continue to monitor since this storm is in an area of 2000-2500 j/kg SBCAPE. Below is an image of the CIMSS CAPE and RUC13 SBCAPE (contour).