GLM: Event Increase Preceeds GOES-16 Overshooting Top

While watching the storms enter our far western CWA, I noticed the GLM Events on the southern storm increased some (near the tip of the western part of the cwa in yellow) around 2010Z. At the same time, the GOES-16 data (upper right) didn't show any stronger areas or overshooting near that storm.

2010Z (UL - All Tilts Radar and ProbSevere, UR - GOES Sandwich, LL - GLM/NLDN, LR - ENTLN)

But when the next GOES-16 scan arrived, you can see the colder cloud tops with the overshooting top, matching the strengthening updraft indication from the GLM.

2017Z (UL - All Tilts Radar and ProbSevere, UR - GOES Sandwich, LL - GLM/NLDN, LR - ENTLN)

At 2022Z, the GLM data increased again, but the overshooting top is diminishing and dissipated on the next GOES-16 imagery.

2022Z (UL - All Tilts Radar and ProbSevere, UR - GOES Sandwich, LL - GLM/NLDN, LR - ENTLN)

In addition, I decided to try out the Stano colortable for a while and this seems to have increased the contrast on the moderate GLM values.

-GOB

GLM Grid Spacing for Events

When selecting the resolution for the GLM 5 min events with 1 min updates, I compared the different sized grids that are being tested in this HWT EWP.  There are definitely double count issues with 10km grid (169 events for nearly the same location).  The 8km grid had zero event areas.  When you zoom out to get the bigger picture for a wider area for storms, the 8km grid became a little fuzzy and you could tell the higher event areas.  The best grid from what I looked at seemed to be the 9km grid (5 min events with 1 min updates), even though the native resolution of the GLM is 8km.

-Dan S.

MetopA issue

Noticed a slight bug or issue with the MetopA this morning.  Most of the yellow dots (microwave only) returned back erroneous soundings that did not look realistic.  Here is an example of one of the yellow dots from MetopA:

Here is a yellow dot example from NUCAPS yesterday to show how NUCAPS is not being impacted by the same issue:

-ISU2004

Storms Nearing Mt Holly CWA from the West

The storms that have been showing a consistently "high" ProbTor value (above 20% earlier) have started to weaken as they near the Mt. Holly CWA.  This weakening can be seen on several of the experimental products.

1952Z (UL - All Tilts Radar and ProbSevere, UR - GOES Sandwich, LL - GLM/NLDN, LR - ENTLN)

In the image above, the ProbSevere values were around 66% due to Wind, the sandwich product had colder cloud tops, and the GLM data was more intense (171 Flashes).

2008Z (UL - All Tilts Radar and ProbSevere, UR - GOES Sandwich, LL - GLM/NLDN, LR - ENTLN)

Moving to 2008Z, the ProbSevere values fell between 30-50% due to wind.  The southern storm in the Sandwich product showed slightly warmer and fuzzy/glaciated cloud tops and the GLM flashes fell to 113. Also notice how the event grid on the southern storm (lower left image) has focused more on the northern storm and matches the trends in the radar and satellite data.

At this time, no plans to issue any warnings on these storms as they enter the CWA. 


-GOB

GLM - Reason for Empty/Zero Pixels in Gridded Event Data

Since I've mentioned the empty/zero pixels in the GLM Gridded Event data over the last couple of days, I thought I would post the reason for it.

In the image below, the blue dots are the GLM Events and the gridded data is the GLM Events that are gridded.  Due to the way that the data is AWIPS grid is verses the GLM data (slightly tilted) it will lead to occasional grids that don't have a GLM event in them.  The 9km data is improved from the 8km data that we have been looking at, but still contains these zero pixels.

Would it be possible to deliver this data at its native resolution and in a gridded form, so we don't run into this issue? Similar to how we get the gridded MRMS data instead of having it calculated on the fly.

-GOB

Mount Holly, NJ CWA - Starting to See Development

Over the last 13 minutes, we are starting to see development in the Mt. Holly CWA.  At 1918Z, there were a few showers but at that time, no lightning present.

1918Z - Little to no lightning in the Mt. Holly CWA

Just a short 13 minutes later (1931Z), two storms have developed in the unstable air mass and are producing a decent number of GLM Flashes.

1931Z - Two storms have intensified in the CWA

Unfortunately, the existing cloud cover has limited the use of the Derived Stability products today.

1917Z - GOES-16 Derived Parameters (UL - CAPE, UR - LI, LL - PWAT, LR - Sandwich)

Looking at the SPC Meso page, there is decent MLCAPE and Effective Bulk Shear over the CWA.

19Z MLCAPE & Effective Bulk Shear

-GOB

ENTLN Cloud Flash Increase Much Greater than GLM: Pennsylvania

Tracking a stout thunderstorms across central Pennsylvania this afternoon, a noticeable trend in the ENTLN detecting a much greater number of cloud flashes, vs the GLM Flashes, granted, these are not a 1 to 1 comparison, this is the most significant and persistent difference I have observed this week.

Near the start of the loop, 18:29z: 23 GLM Flashes vs 28 ENTLN Cloud Flashes

At 18:32z, the ENLTN begins to distance itself from the GLM.

 At 18:46, the ENTLN maintains it's large spread on the GLM, 182 to 104.

At 18:53, the ENLTN reaches it's greatest spread from the GLM, 353 to 134.

Of note, during this time period, the NLDN and ENTLN had nearly identical strike counts, for both positive and negative strikes.

Dale Doback

GLM Flash Density

Comparing the flash density for the 5, 8, 9, 10 km grids.  It looked the the 9 km grid had the least amount of data drop out areas to make the lightning fields look more continuous.  Here is a loop of lightning data from southern Ohio/Northern Kentucky showing the differences in the resolution.

5 km has way too many drop off areas and just looks strange, while the 9 km looked the best overall.

Pueblo convergence zone

Pretty good surface convergence zone setting up over Pueblo this afternoon with convection firing up along the boundary.  GLM has been active along some of the line.  Prob severe has been handing out in the single digits and storms are having a tough time sustaining a good depth.  However, storms will continue to move into an area with high CAPE values this afternoon, so some storm strengthening with time seems very likely. 

Convergence zone (noted with white lline) with GLM overlaid.  Shading is events, and plotted is flashes.  This is one of the experimental color curves begin tested this week.

-ISU2004

ProbTor and GLM Comparison

Here is a loop of the ProbTor overlayed on the MRMS Rotation Tracks (Upper Left), along with GLM (Lower Left), ENTLN (Lower Right) and Sandwich GOES-16 (Upper Right).

~80 minute loop over central Pennsylvania

The thing to take notice of in the lower left loop is how the GLM lightning flashes/events quickly ramped up just ahead of the highest ProbTor values (74%).  That GLM increase highlighted the intensifying updraft in the storm.  In addition, when taking a close look at the MRMS Rotation Tracks, you can see increases around the same time or just after the GLM events/flashes increase (possible lightning jumps).

One item that I did notice with the 9km GLM data with this storm is a few pixels of no data (notice it during the first half of the loop and again near the end as the storm moves directly over one of the spots where the lightning data doesn't match with the AWIPS grid.

Example of zero data due to the grid in AWIPS at 1809Z.

 -GOB