GLM – Florida Coast

Convection off the coast of Florida developed into a few organized strong to severe storms over marine zones. GLM Flash Extent Density (upper left)  was far and away the most useful of the GLM products available for warning operations. The strongest storms were the most evident on this product compared to the others, and rapid lightning increases were most easily noted. This allows for quick use of the lightning data for situational awareness and setting priorities when there are numerous storms to interrogate. The other GLM products generally washed out any signal of which storms were the strongest, and didn’t provide as much information about overall storm trends.


The rapid 1-minute update times that can be linked with 1-minute meso sector satellite imagery and 2-minute MRMS data can allow for more rapid warning decisions (and thus more lead time) when all considered together with base radar data.

Compared to ENTLN 1km total flash data, there wasn’t much difference in warning utility between the two products. The same information can be derived from each product in terms of storm intensity and picking out the strongest updrafts. I would give a slight edge to the ENTLN in terms of product display as the smaller grid allows for better viewing of the background satellite imagery. However, the spatial extent aspect of the GLM has advantages for public safety messaging. So overall a very even match between the two products.

— warmbias —


Fun 30 minutes of storms in Florida

There was a nice area of convection moving off the east coast of Florida with storms forming off an apparent outflow boundary moving to the south. As the storms moved off the coast they increased intensity exponentially. Focusing on these storms as they moved over water reflectivity showed max dBzs in the low to mid 60s with tops 45-50k ft high. GOES-16 Event density (5min-1min update) showed a value of 247 suggesting a nice updraft, which AzShear seems to further support with a bright white color and value of .007s^-1 exactly where the max dBzs/echo tops/GLM data is. In addition,prob severe did a good job of tracking the storms…but with the storms moving off the coast it is impossible to get any storm reports to verify its accuracy.

Utilizing all of this data I would most definitely want to issue a localized small craft or some sort of marine advisory or warning…if there was one for this are. -Desmond

AzShear .007s^-1

GOES-16 Event density (5min-1min update)

Max dBzs in the low to mid 60s


Convection on LL PW Gradient

Convection began along a low level PW gradient across NW OK per GLM Flash Extent Density. Expected forecast: Based on steering flow, the storms should move into a more moisture rich environment and expand in coverage.

2027Z Upper Left: TPW, Upper Right: Sfc to 0.9 sigma PW, Bottom Right: 0.9 to 0.7 sigma, Bottom Left: 0.7 to 0.3 sigma PW

A little while later…Storms continued to expand eastward along the gradient into the more moisture rich environment.

2228Z Upper Left: TPW, Upper Right: Sfc to 0.9 sigma PW, Bottom Right: 0.9 to 0.7 sigma, Bottom Left: 0.7 to 0.3 sigma PW

-Tempest Sooner

Event Density with RGB Composite VIS/IR Sandwich

Image 1 shows the  GOES16 RGB Composite VIS/IR Sandwich.  This product displays the texture of the convective cloud tops and the temperature of those cloud tops.  The texture and temperature of the clouds provides information about the updraft.  The 2nd image shows the most intense GOESR GLM event densities and how they correspond with the taller clouds and strong updrafts. – Jonathan W. Smith (ESSIC/UMD) .

Good non-severe storm with agreement from radar/satellite products

One storm became near severe around 545 pm in EWX CWA. All parameters; lightning, ProbSevere and Dual-pol radar agreed on the evolution of the storm and expected impacts. Radar data suggested there to be equal wind and hail threat based on high ZDR and KDP within the core suggesting sub-severe hail. There was some notching in the back side of the storm’s reflectivity as the front end of the storm surged eastward suggesting some wind threat. Lightning over this time had increase from 10 fl/min to 20 fl/min about 15-20 minutes prior to the development of some weak mid level rotation. As the storm cycled and weakened, so did the lightning and ProbSevere values. An uptick in GLM event density was followed by a slight increase in ProbSevere values toward the end of the loop.

KEWX 4-panel – Refl (UL), ZDR (UR), KDP (LL), CC (LR)

KEWX 4-panel – SRM (UL), V (UR), HC (LL), SW (LR)

GLM sequence of Gillespie County storm – 1-min(FED)(UL),AFA(UR),TOE(LL),EventDensity(LR)

ProbSevere time trends from

— SCoulomb

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 MOEvent 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.


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.