LtgCast Precursor to Storms Diverging

LtgCast gave advanced indication (about an hour) in the FWD region that the northern storms were diverging to the north away from the original track that was more easterly. Below you can see the LtgCast extending to the north into clear skies in the first two images. The next four pairs of images are the LtgCast paired with the radar at about the same time. The last two images are the next 20 minutes of radar.

In the TAE area, the LtgCast wasn’t as effective. Behind the storms, LtgCast kept >75% probs for lightning in clear air as seen in satellite imagery, possibly as much as 50 miles or more. This was odd in that it usually quick to pull in the probs behind the storms. It wasn’t that the storms were slow moving or inconsistent in their motions; they were moving uniformly to the southeast at a constant rate (didn’t measure the speed, but would estimate the line speed 20 kts or more).

– Super Bolt

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Lightning Jump in GLM FED, but not Earth Networks data

Storms continue just after 7pm near the Oklahoma/Texas border. A currently severe-warned storm saw a substantial and rapid increase in lightning activity observed by the GLM Flash Extent Density product. However, the ground based lightning network did not follow the same trend and remained fairly steady. The ground based data is more reasonable considering the storm did not experience any sort of significant strengthening during this time period. Earlier discussions with lightning detection experts suggested the low GLM FED count may be due to the location of lightning within the storm updraft region, which could impact how well GLM can sense it. That is difficult for the typical operational meteorologist to consider in real-time since it goes well beyond current training, and leads to decreased forecast confidence in the lightning data.

Dave Grohl

Minimum Flash Area Shows all the Features

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:


Lightning Jumps in Action

The storm near Tulia is…impressive.  Aside from being a long-tracked supercell, the storm has been extremely active electrically.  There have been several lightning jumps with this storm that appears to coincide with an increase in the strength of the mid-level mesocyclone.  First we will take a look at an hour long loop (TL – Flash Extent Density overlay with Vaisala GLD, TR – Minimum Flash Area, BL –  Optical Energy, BR –  Mid-level Azimuthal Shear (3-6 km AGL) with New Mesocyclone Detection Algorithm Overlay) :

There are two jumps to take a look at, 1) between 21:29 and 21:40, 2) 21:55 – 21:20.  Although the AzShear product doesn’t show a strong mid-level meso developing, the number of positive CG flashes in the GLD data increases and we see continued small area flashes in the core.  The more impressive jump is the second one;  AzShear shows a much more pronounced area of positive shear, a long-lived NMDA indication (the circle with 4 pips on it), and overall smaller flashes in the area of that storm.

Shortly after the last jump (and not shown here), live stormchaser feeds showed a rapid strengthening of low-level features; well defined wall cloud, organized rotation, and frequent CG activity sending a flurry of stormchasers heading east to get out from under the storm…


Big, Bad, Flash or Bad Big Flash

Everything was chugging along great with the GLM and the storms around Amarillo this afternoon as this image from 19:54 shows (TL – Flash Extent Density 5-minute w/ 1-minute update with Vaisala GLD Data overlayed, TR – Minimum Flash Area with ENI Total Lightning overlayed, BL – Total Optical Energy with Vaisala NLDN overlayed, BR – IR/VIS Sandwich):

But then the next set of data arrives at 19:55:

So, that big white area showed up which is a 2918 km2 area flash.  WOW.  THAT. IS. HUGE.  But the question now becomes is that correct or not?  Taking into account parallax and the data from the ground-based networks shows that there was electrical activity in the general area.  However, it isn’t in the area that would line up with the parallax; the ground-based network data should be closer to the southeastern area of the flash.  Also of interest is that there is no Flash Extent Density associated with the large flash but there is an associated area of Total Optical Energy.

One thing we are tossing around here is the possibility of a cloud reflection; here is the 1-minute visible mesoscale scan with the big flashes overlayed:

If there was indeed a flash at this time, the optical energy could have reflected from the originating area off the anvil, and then reflected back off the low clouds around the updraft to the GLM instrument.  However, the fact that there isn’t any data associated with this flash in Flash Extent Density is concerning.  Needless to say, the lightning scientists here are all going “Hmmmmmmm….”


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.



Severe Thunderstorm Warning #2 – Oklahoma

Pulled the trigger on the second severe thunderstorm warning of the day. Radar signatures (60 dBZ to -20C, TBSS) began to indicate hail was possible at roughly the same time that ProbSevere jumped to around 80% and there was a 7-sigma lightning jump. I was ready to pull the trigger when I saw the radar signatures, but the ProbSevere and lightning jump gave me more confidence on the warning.


-Toki Wartooth

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