Today's Experimental Operations - May 1, 2019

Today's operations will be focused over the OUN (Norman), SJT (San Angelo), and FWD (Dallas/Fort Worth) county warning areas.  We are highlighting operations south of a remnant outflow boundary that has been left from storms that occurred overnight/early this morning roughly in the area of the Red River Valley.  Storms are currently on-going at the start of operations, with a severe thunderstorm watch over the operations areas that stretches from central OK all the way down to SW Texas.  Supercells will be the primary storm mode to start but might transition to a linear system later in the operations period.  The main threats today are large hail and high winds but tornadoes are still possible (lower probabilities than yesterday though).

Mesoanalysis of Storm Development

Figure A
Lightning and ProbSVR detection of first storm develop in west Texas.  GLM products high-lighting two updrafts at 1810Z in Figure A.





Lightning really increased showing lightning jumps and ProSVR Hail/Wind greater than 90% in time series trends.  Notice Tornado trend increased slightly with lowering wall cloud report, however environment is not as favorable for tornadoes today with 0-1km shear on the low end.

A Quick Start to the Convective Day

After our day 2 debrief, forecasters began operations as severe thunderstorms were already developing over the OUN and SJT.  A common theme from the day 2 debrief, was forecasters really liked the trends captured by ProbSevere.  While work continues on getting ProbSevere time series plotting capabilities in AWIPS-II, forecasters are utilizing time series capabilities from the ProbSevere website.  Forecasters mentioned they appreciated being able to quickly see how the first storms evolved by using the ProbSevere time series.  Also noted by forecasters were strong satellite growth rates and very high CAPE in the hail growth region lending to very rapidly increasing ProbHail values, even before MESH reached 1.00".

ProbSevere time series capability from the ProbSevere website for the first severe thunderstorm of the day in the Norman WFO, near the Red River.

AWIPS-II 0.5 degree reflectivity and NOAA/CIMSS ProbSevere for the evolution of a rapidly developing thunderstorm near the Red River on May 1 2019.

-J. Sieglaff

Remember to look underneath the hood

Here's another example where a casual look at ProbTor might cause some confusion. Flow parallel to the boundary across the OKC metro eventually won out and the semi-discrete cells merged into a messy, slow-moving mess shortly before 22z. At 2148z, ProbTor peaked at 74% for the mass of convection just NE of OKC. However, KTLX velocity showed no immediate areas of concern. The answer to the high ProbTor was found in the 0-2km merged AzShear product. AzShear showed an enhanced area of shear to the NE of OKC near Spencer with generally convergent and broad flow. This is a good example of how ProbTor can be useful in operations: it quickly highlights areas for further investigation that can either be confirmed or thrown out with a very quick interrogation of the base data. In this case, ProbTor worked well, it was just biased by the abnormal/noisy AzShear data.

--Stanley Cupp

2148z KTLX base refl (top), base velocity (middle), and 0-2km AzShear (bottom) with 74% ProbTor contour overlaid on each

Why hello friend - merging supercells into a single ProbTor Object

Here a strengthening southern supercell invaded the personal space of its "more aged" northern neighbor. The merger did not change the  ProbTor values of the original, stronger storm (90%) but did eventually show a slightly lower value (87%) despite the southern storm becoming more intense in rotation. There were only subtle differences noted in the ingredients and nothing stood out as to why the Prob values dropped.

As for the new mesocyclone algorithm (xmda) the strength rank jumped to 25 (max value) at 23:32. It is difficult to follow the individual storms in the attribute table since they jump from page to page and are ordered by ID versus strength. Having the cell ID color coded at certain values (e.g. above 10 colored yellow, above 15 colored blue, etc.) would help more quickly discriminate the strongest mesocyclones, especially if you have to move to another page. ProbWind (lower right panel) continues to be very high for these supercells (consistently >90%) although no wind reports were received by SGF.


0-2km AzShear/ProbTor (UL), 3-6km AzShear/xmda (UR), HI/ProbHail (LL), Z/SRM/ProbWind (LR)

AllSkyLAPS900mb - Dryline

AllskyLaps900mb layer PW product does an excellent job in tracking evolution of dry line over west texas on 4/30/19

-Quik Twip

All Sky Total Layer PW versus CIRA merged TPW

Figure A


Figure B

All Sky Total Layer PW did a better job in Figure A with western gradient of moisture where convection developed along dry-line compared CIRA Merged Total PW.  All Sky also seemed to better capture the moisture plume through central Oklahoma into southeast Kansas.

-Jake Johnson

HWT day 2: 19:10 GLM and AzShear observations of Missouri tornadic supercell

Feature following zoom showing the GLM pulsing phenomena associated with intensification/weakening of a supercell in OK/MO. During the third pulse, a TOR warning was issued.


Case of CPTI values on a confirmed tornado near Miller, MO. No confirmed damage estimates yet, but TOR was confirmed at this time visually and with a TDS


Lightning jump preceding a tornado and then confirmed touchdown in MO

Event Density over the same cell

Minimum Flash area showing updraft core


Average Flash Area



This is a case where AzShear overdid the tornadic threat This supercell had a circulation that never really tightened up. ProbSevere also vastly overestimated the tornado threat, likely due to nearby storm interactions and mergers. When convection gets messy, can we rely on these products as much?



The two images above compare a 4 panel of 1 min GLM data (left four panels) versus 5 min data (right four panels). While the 5 min data was much smoother to view from an animation and trend sense, the 1 min data did provide some fine temporal resolution help during periods of rapid storm intensification preceding this tornado warning.



The above two loops compare 1 min looping (top 4 panel) versus 5 min looping (bottom 4 panels). In a loop the 'flashy' nature of 1 min data makes it less desirable in operations, however manual toggling and advancing still make this data useful.

Max Value Readout for GLM in upper left of screen?

GLM FED maxed out at 160 fl/5-min and TOE at 580 fJ on this cell in southern MO. It would be nice to have the maximum value, at least for the FED and TOE products in the upper left corner like the ground-based networks have. This would also help with quantifying things such as lightning jumps or quickly comparing two cells.


GLM FED (UL), AFA (UR), TOE (LL), RLA (LR)

-- SCoulomb

HWT Day 2 case blog: Start until 19:10

This rapidly developing supercell displayed a GLM lightning decrease as it intensified. This was a good example of optical attenuation due to an updraft core. ENTLN network is displayed, showing that there was a tremendous of CG and IC flashes despite low GLM values. Shown is the TOE product.



The same storm and lightning minimum shown in Event Density.



ProbTor was occasionally too aggressive. Only one of these storms was really concerning at this time given the environment and radar tilts further up in the volume. On a day like this, it would likely be prudent to increase the probtor threshold above 3%



Prob Tor contours showing  a new probtor threshold of 10% instead of 3%. This was edited on the fly in the localization file of the procedure itself. This view shows a less cluttered display given the amount of rotating storms this day.



Comparison of MDA products over a weak low topped supercell, as well as showing the probsevere contours. ProbTor was at 47% at the time, prompting the issuance of a Tor Warning.