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As we move towards sunset, the MCS continues to munch across the southeast Tejas, Louisiana, and portions of Arkansas. There is alos a strong storm developing ahead of the MCS in SE Louisiana. Add in some storms across Northwest OK and there is whole spectrum of flash sizes is showing up now:
What is neat about this image is that the small flashes (purple) are concentrated near the overshooting tops of the storms. The large area flashes (red to white) are in the trailing stratiform area.
One other cool tidbit I just saw in this loop; watch the southwestern part of the line where a storm weakens and dissipates; flash area basically shows that all electrical activity ceases along with the storm. Looking closer:
In this case of a rapidly developing storm, GLM data was leaned on to issue a SVR Warning on what otherwise may have been a marginal storm. AllSkyLAP showed the storm was developing in an area of MLCAPE values over 2000 J/kg, and ProbWind model had rapidly increased to ~50%. GOES-16 1-minute imagery showed rapidly cooling cloud tops, with a sharp increase in lightning activity. Given GLM values comparable to other severe storms on the day a SVR warning was placed on the storm. The warning was sent out relatively early to try to capitalize on lead time.
Radar w/ ProbSevere:
IR-Sandwich:
Flash Event Density:
Minimum Flash Area:
Event Density:
Total Optical Energy (too fast, whoops!):
AllSkyLAP CAPE:
ProbWind Model Increase:
UPDATE: Shortly after warning on the storm, it completely fell apart after failing to become rooted in the boundary layer and all indicators (i.e., ProbSevere, GLM imagry) dropped to null. Initial warning was shamefully cancelled.
At 2127 and 2157 UTC on 8 May (exactly six hours after it was previously noted), a surge in TPW in a cloudy region (Northeast TX region). This might be a predictable behavior in All-Sky LAP and points to improvement needed in how it handles new model cycles. Similar jump behavior was noted in All-Sky LAP CAPE.
In trying to give due diligence to all of the products I decided to look at the NUCAPS soundings a little deeper today. The location of the sounding point was around 9 mi SE of Ruston Regional Airport in an area that was impacted by a weak line of convection moving across central Louisiana, as shown in the METARS from KRSN.
Both soundings passed the QC checks and were towards the center of the swath. So what did NUCAPS show? Here are the lowest levels of both the NUCAPS and Modified NUCAPS soundings at 19Z…
NUCAPS Sounding at 19ZModified NUCAPS Sounding at 19Z
The NUCAPS sounding had a temp of 21.92C (71.47F) and a dew point of 16.18C (61.12F). The modified NUCAPS sounding had a temp of 20.81C (69.46F) and a dew point 17.72 C(63.87F).
For comparison here are the RTMA temp and dew point between 17-19Z at the sounding point and at KRSN…
It makes sense that the RTMA dew point depression is small given the recent rains, and if the RTMA is suppose to be the ground truth, it looks like the NUCAPS soundings did a bad job in this case. Temps for the NUCAPS soundings were 2-4 degrees cooler which is okay, but the modified sounding was cooler. It would have probably been better to keep the temp from the unmodified sounding. With regards to dew points, both the modified and unmodified soundings had lower dew points than RTMA, on the order of 6-7 degrees. These definitely affected the thermodynamic calculations, though I’m pretty positive that it was the mid-level inversion that did the most damage. I’m not sure how to fix this since only the surface points get modified.
Anyways, hindsight being 20/20, I probably should have looked at an area that wasn’t recently impacted by rain, but by the time I realized it it was too late and I already gathered all the data. Anyways, both NUCAPS soundings in this case did not accurately represent the environment in the lower levels, likely a result of evaportaive cooling and outflow behind the line of convection. This is a word of caution that despite the soundings passing the QC checks (the points were both green) and being in the center of the swath the data may not be the most useful.
Isolated convection trying to develop across TX Panhandle. GLM Average Flash Area product picking up on initial lightning activity within the developing convection.
Big flashes taking place in the stratiform region of the departing MCS across the eastern third of Texas. A LOT of big flashes:
But that doesn’t tell the full story; there are a LOT of big flashes but they are being masked by the scaling of Flash Area. Right now the scale runs from 64 km2 to 2000 km2. What happens if we bump that max side up to 4000 km2?
There we go, a bit better discrimination on the big-side of the scale! It may be hard to see but there is one “white” flash in there; a slightly larger 4600 km2 flash southeast of DFW.
That. is. Yuuuuuuuuuuge.
So, lesson of the day; check the values of flash size (or any flash component). See if there are values past the end of the current color scale. Right click on the appropriate product, select Change Colormap , and bump that up some. May be able to pull out a bit more information than what comes as the default. Once again however…YMMV.
Example from KAMA radar showing how the legacy MDA (top left) and DMDA (top right) are falsely indicating mesocyclones with general thunderstorms along the OK/TX border, while the NMDA (bottom left) does not indicate a mesocyclone. Noisy velocity data may be resulting in the false meso indications.
In general, the performance of the NMDA along the thunderstorm line moving across the northern SHV CWA has been superior to both the MDA and DMDA in terms of more accurate detection of greatest, often small, regions of cyclonic vorticity along the leading edge of the line that I’d likely be issuing TOR warnings for as a warning forecast in the SHV office today.
Here’s a case where the ProbTor model significantly increased in an area where tornado potential was extremely limited. Below are animations of the radar velocity at the closest radar (KGRK), the low-level Merged AzShear, and the time series of the ProbSevere product. The cell in question was small and behind the main line of storms in the more stable airmass, yet the ProbTor model jumped to 79% for several minutes. The time series seemed to indicated this was due to an increase in AzShear yet the Merged Low-Level AzShear product showed no distinct signature (same for Mid-Level AzShear not shown).
UPDATE:
After consulting with the fantastic Mr. Cintineo, he found that the false flags were likely from a jump in the Low-Level Rotation tracks in MRMS (shown below). These false signatures, however, were not making it into the aforementioned AzShear product.
Modified NUCAPS sounding for Bienville county in SHV CWA in advance of line we have severe warnings out for with embedded tornadic circulations.
Comparison of NUCAPS soundings in pre-storm environment in SHV CWA. We’re warning for a bowing segment line with bookend vortices. There are several important differences between the generated soundings, including a better representative moisture profile from the modified sounding given the moist environment, linear convection, precip. loading processes. Also of note is the inversion shown between 900 and 850mb in the operational sounding. Analysis of the RAP13 850 temp fields suggest the modified sounding is more representative of what’s likely occurring. In this instance the NUCAPS modified sounding appears to be a better product for the current environment.
Operational NUCAPS sounding for Bienville county in SHV CWA in advance of line we have severe warnings out for with embedded tornadic circulations.
