Comparison of Operational NUCAPS / Modified NUCAPS

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.

Surging in All-Sky LAP TPW

We’ve seen a couple of cases where the All-Sky LAP TPW surges back and forth unrealistically over a half hour intervals.  Here are three frames 1/2 hour apart from 1458 / 1528 / 1557 UTC 8 May 2019.  Note the surging TPW over the eastern OK / northwest AR region.

1458 UTC

1528 UTC

1557 UTC

1458 UTC Data type (yellow / gray cloudy)

The data type indicates this is in a cloudy region.  What’s odd is the middle frame is different, then the last frame is more like the first.  Perhaps this is related to handling of the new 12 UTC GFS cycle?

JohnF

 

GLM Activity In Developing Line of Storms

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

 

MDAs with cycling supercell

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.

GLM Data Helpful Far From Radar

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?

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…

Increasing GLM activity in a dying storm

At 2330Z, GLM began picking up a signal of increased lightning activity with a storm moving into the LUB CWA. At the time the core was strong with a spike in value in the MRMS VII product, though real-time radar had started to show a weakening storm. (Left panel shows GLM Event Density)

10 minutes later, at 2340 UTC, the storm was deteriorating, yet GLM Event Density continued to increase in this area while ENTLN Total lightning data was decreasing.

After another 10 minutes, at 2350Z, GLM lightning activity continues to breanch eastward despite little reflectivity aloft and ELTLN lightning continuing to decrease in the area.

Finally, at 2352Z, 2 minutes later there’s a rapid decrease in the lightning activity on GLM in the easternmost storm. The Event Density data was the 5min-1min update, and it looked like 1 minutes worth of data was the result of the eastern extension.

#ProtectAndDissipate