GLM Activity In Developing Line of Storms

Posted in Live Blogs on by Justin.

The outflow from the main line of storms was moving west and combined with a strong cell which was spawned off the dryline, resulting in a strong line of storms forming where the two converged. Something that was noted was the delay in GLM FED with the developing convection, where flashes could be seen quickly from the ENTLN. Chalked this up to the optical depth of the storm at the time covering the flashed from the GLM given the extent of cloud-to-ground strikes. Later on, a line of increased GLM FED could be seen.

#ProtectAndDissipate

 

GLM Viewing Angles – what it means

Posted in GOESR, HWT on by Tiffany.

Having both GOES-E and GOES-W GLM data provides some interesting opportunities to compare how the two instrument’s viewing angles impact the data.  Sometimes it does, sometimes it doesn’t.

First case, it confirms the large flash size in a flash across the Texas and Oklahoma Panhandles into Kansas: top image is GOES-W and bottom image is GOES-E.  The white flash is over 2000 km2; G-17 was 2140 and G-16 was 2685.  Not bad!  This was probably a flash extending  from convective cores in northwest Oklahoma back into the anvil region.

But now let’s look at a different flash; this time a bit further south.  The top image is G-16, bottom is G-17.

The white flash in G-16 was shown as a 2262 km2 flash while G-17 in dark red was only 1096 km2.  Why the big difference?  Probably the different viewing angles.  The image below is centered on a strong overshooting top that the flash in question above originated around:

G-16 has a more favorable viewing angle on this flash looking towards the updraft/overshooting top from the southeast.  G-17 may have had some of the weaker portions of the flash blocked by optical depth of the anvil or being underneath a part of the overshooting top.

The implications are that depending on the orientation of the storm to the GLM instruments; checking both will perhaps provide confidence in the evolution of Flash Area and potentially other GLM flash products as well.

-Dusty

ProbSevere Split It

Posted in ProbSevere, Pseudo GLM on by Michael Bowlan.

Quick update to a previous post. Like before, the first image shows GLM Event Density and the second shows base reflectivity with ProbSevere. It took ProbSevere’s tracking algorithm around 15-20 minutes to  splitting the storms into multiple ones. I would have been awesome if it happened earlier, but I’m not complaining. It happened quicker than I thought it would.

MDAs with cycling supercell

Posted in Live Blogs, NMDA on by Tiffany.

The NMDA (bottom left) tracked a weakening meso and picked up on a new strengthening meso with a cycling supercell. The legacy MDA (top left) and DMDA (top right) lost the old meso before the NMDA did. To this forecaster, it is important to still know the location of the weakening mesocyclone, which the NMDA helped locate.

Will these storms split finally in ProbSevere?

Posted in CG Ltg Probability, ProbSevere, Pseudo GLM on by Michael Bowlan.

Below are a few images for a long-lived storm in Pecos County that is starting to split. The first image shows GLM Event Density with two separate hot spots while the second image shows base reflectivity  with ProbSevere contours. It will be interesting to see if/when the ProbSevere tracking algorithm will splits the storm into two storms rather than one merged storm.

GLM Data Helpful Far From Radar

Posted in Live Blogs on by Michael Bowlan.

GLM data is helpful to me, and visually I find more effective than other point lightning data and giving me storm intensity information as the storms get farther away from the CWA radar and other scopes that can see them. Because of the radar location related to the storms, radar based data sets are becoming less useful at this time.

GLM Data – How To Visualize?

Posted in HWT, Live Blogs on by Tiffany.

The GLM data is showing a lot of utility and provides useful information on storm trends, intensity, and storm mode.  However, the biggest issue is how to visualize all this information and tie it to the meteorology; the “physics-science” side of things in order to tie everything together.

Here is the first attempt and why:
Top left panel – 5-Minute Flash Extent Density with 1-minute updates (enhanced color curve): this is a good way to see trends with the GLM data as it is a 5-minute window updated every minute.  Shows increases/ in lightning flashes with time with a “smoother” display rather than just every 1-minute frame.
Top right panel – 1-minute Minimum Flash Area (enhanced color curve): shows where the smallest flashes are occurring.  Rough reason; small flashes corresponds to strong updrafts with lots of turbulence limiting the extent to which flashes can develop.  So, small flashes (around or under 100 km2) should correspond to strong updrafts.  Works with both multi-cellular, super cellular, and pulse convection. Don’t use the 5-minute with 1-minute update because the tendency I’ve seen so far is that it can result in an area of small flashes that is way to large for an individual storm updraft as it covers where it has been for the last 5 minutes!

So, how to tie this into the meteorology.  There needs to be some way to show “ground truth” outside of the ground-based lightning detection networks.  So, let’s give this a try:

Bottom left panel – MRMS composite reflectivity at -10 C.  This shows strong convective cores that are capable of producing mixed-phased precipitation needed for lightning.  MRMS because it can cover areas with storms that are within the Cone-of-Silence for any given radar.  Going with -10 C gets above the melting level at 0 C and below the -20 C where the majority of particles should be switching over to more ice crystals than liquid and/or large hail.
Bottom right panel – 3 to 6 km Merged Azimuthal Shear.  If done right, this should show when mid-level mesocyclones are starting to strengthen and where rotation would be the strongest.   Strong updrafts that are rotation can help a storm produce small flashes (again, the whole turbulent mixing in and around the updraft thing).

Is this the best way to do this?  No idea!  It’s a start though and as we go through the following 6 frames, you can hopefully see how this plays out.  Watch the southern-most storm have high Flash Extent Density counts while the Minimum Flash Area remains around 60 km2.  Although there isn’t a strong sign of rotation in the AzShear product, the GLM data shows that there is a strong updraft that has maintained strength over the last 6 minutes.

Watching the northern storm, AzShear shows stronger rotation and a quick check of the base data (not shown Z, V, SRM) shows that there was a weak but persistence mesocyclone with the northern storm.  With time, the AzShear product shows strong cyclonic shear with this storm and we start to see the FED increase while flash sizes decrease.  It takes some time but after around 5 minutes, the Minimum Flash Area had bottomed out around 60 km2.

This isn’t perfect by any means.  Another issue to look it is how to incorporate this into warning operations because this is a lot to look at.  At this point, GLM data may be too much to add in a single-person warning situation.

Something to consider…