pGLM colormap (comparison)

As the MCS moves towards the Northern Alabama LMA, I thought it was a good time to compare colormaps and get feedback from each of the forecasters.

I added the following image to the large screen of the situational awareness display within the HWT and asked each forecaster which colormap they preferred – the one on the bottom left or the one on the bottom right.

top left:  200 km2 LJA over MRMS lowest refl.  Top right: 600 km2 LJA over refl at -10 C.  Bottom left: PGLM flash extent density (colormap 1).  Bottom Right: PGLM flash extent density (colormap 2)
top left: 200 km2 LJA over MRMS lowest refl. Top right: 600 km2 LJA over refl at -10 C. Bottom left: PGLM flash extent density (colormap 1). Bottom Right: PGLM flash extent density (colormap 2)

All forecasters this week preferred the colormap on the bottom left except for one specific case:  when they want to overlay the data on radar.  For that particular occurance, the bottom left is a bit to similar to the radar. However, all agreed that on its own or overlaid on satellite the colormap on the bottom left is much preferred. (note: the colormap on the bottom right is the default colormap for AWIPS2).

-K. Calhoun



Total Lightning to forecast strengthening storm

lightning data


I have been watching the Total Lightning product over the developing storm and it shows both flash initiation density and flash extent density that have been increasing over the last 30 minutes.  That coupled with the increase on the Prob Severe, would lead me to believe this is nearing severe limits and I would then issue a warning.  I really like these products because it shows where the updraft is developing and also where hail would be found. ~ Vollmar

Same Storm Different Lightning Jump


A secondary lightning jump occurs at 23:28 UTC with the same storm east of Denver Co. The lightning jump here reached the 2 sigma level when the total flash rate increased from 8 flashes per minute to 16 flashes per minute in the span of two minutes. This reinforcing lightning jump indicates that the storm’s updraft was still undergoing periods of intensification.  Baseball size hail was being reported at the time of the jump, and ping pong ball size hail was reported at 23:35 UTC in association with this storm.  Hail was reported as deep as 3 inches on the ground.

*There appears to be a delay between the jump occurrence in the Flash Initiation Density (23:28 UTC) and the LJA sigma plot (23:33 UTC).

PGLM, Lightning Jump, and Quarter size hail


Example lightning jumps from just east of Denver CO at 2251 UTC. The image above shows the lightning jump feature (shaded purple), flash initiation density (FID; pink boxes) and the meteogram output information.  The top two panels are the sigma levels at which lightning jump occurs, and the bottom panel is the total flash rate from the PGLM.   The Tracking meteogram outline is the white circles encompassing the storm.  Two lightning jumps occur at 2249 and 2251 UTC.  The first jump occurs as the total flash rate from the PGLM reaches 10 flashes per minute (4 sigma level; anything above 2 sigma indicates a lightning jump according to Schultz et al. 2011), and the second jump occurs with the larger increase in total lightning from 5 flashes a minute to 15 flashes per minute (6 sigma).  The jumps are indicating increases in updraft strength and volume,and can be used as a metric in storm intensification.  Quarter size hail was reported approximately 20 minutes later at 2310 UTC.

*note the flash rates are likely higher with this storm because the LMA used in this case only had 5-8 sensors active at any given time.*

Evaluating the Total Lightning Tracking Tool

Posted by Geoffrey Stano – NASA SPoRT

The 2013 Experimental Warning Program (EWP) has offered a great opportunity to test the NASA SPoRT / MDL total lightning tracking tool. Part of EWP’s efforts are to demonstrate future GOES-R capabilities, such as the Geostationary Lightning Mapper. This is being done with the pseudo-geostationary lightning mapper products being produced by NASA SPoRT in collaboration with seven ground-based total lightning networks. With total lightning observations (intra-cloud and cloud-to-ground) forecasters are looking for lightning jumps, or very rapid increases in total lightning activity ahead of severe weather. In the past, this has been done by visually inspecting the PGLM data. From previous evaluations by both SPoRT and the EWP, the number one request was for a way to visualize the time series trend of total lightning in real-time. With AWIPS II and the ability to create custom plug-ins, the first effort for this has been developed and is now here in operations at the EWP. One design feature was to make this a manual tool. In other words, it is the forecaster who selects the cell track and not an automated tracker, which traditionally has difficulty with merging and splitting cells or not activating at the proper time. Once the forecaster places two points, the tracker activates and will create a track based on these points.  Each point can be moved individually to adjust the track and the tracker will attempt to maintain the track as new data are ingested.  We wanted to evaluate the utility of the total lightning tracking tool as well as its impact on operations. In only a couple days, the feedback has been great. First, here is an example of the PGLM with the total lightning tracking tool this evening.

The PGLM flash extent density observing a maximum of 50 flashes with the total lightning tracking tool time series (pop-up to left).
The PGLM flash extent density observing a maximum of 49 flashes with the total lightning tracking tool time series (pop-up to left).  The lightning jump can be seen early in the time series as it goes from 20 to 49 flashes in two minutes.

Overall, feedback has been very positive as forecasters have  appreciated being able to visualize the time series instead of creating a mental picture.  Also, the time series plot is pinned to always be on top, which prevents it from being lost behind the D2D display.  Also, the feedback has been very constructive to help improve the look and provide ways to minimize the time impact.  Some of the commentary has focused on modest improvements to the layout and look.

  • Add a minimize button to the time series display pop-up.
  • Have the time series trend color match the active cell point color for the track.
  • Have a way to change the default size of the cell point radius of influence (which determine how much lightning data to query).

The feedback also has included very interesting options to save time in implementation.

  • The tracker initiates after two points are plotted.  However, it attempts to extrapolate the cell track after placing one point.  This results in the cell points being very spread out.  Suggest waiting to extrapolate the track until after two points placed.
  • Also, when the storms are more discrete, instead of using individual cell points created a small “domain” around the storm cell of interest.  The forecaster selects a “polygon” of where the storm will be and the tracker selects the PGLM value within this domain at each time step. This may be able to be done by using the tools similar to how forecasters plot a warning polygon as well as how that can be edited.  Furthermore, the storm motion could be added to further aid the plot.  The big advantage here is that this polygon may be much quicker to place than several individual cell points.

All of these are very good suggestions and this feedback will be taken back to see what can be implemented. The polygon suggesting is very interesting to consider, while the current cell point method would be most viable in a multi-cellular environment.  Additionally, this feedback has been very useful in that it helps refine the total lightning tracking tool ahead of its next evaluation as part of the Operations Proving Ground later this summer.

Tomorrow should be another good day to gather additional feedback.


Lightning Jump Data Collection Summary: 31 May 2012

An earlier post summarized the first month and half of data collection, the details below will bring us through the end of May.

Note: All times are approximate to include timing of any severe or marginally severe weather in the domains.  Re-processing and analysis should start prior to first time listed here. SHAVE details are included for dates that I personally know they collected data over the domain.  Dates without “SHAVE ops” listed may also have SHAVE data, please check directly with Kiel Ortega if you need it for analysis.

17 May 2012: FL-LDAR, 2230 UTC – 0100 UTC (18 May), SHAVE operational

19 May 2012: OKLMA, 2200 -0800 UTC, SHAVE ops in OK domain

20 May 2012: OKLMA (maybe, on edge of 3d); 2100 – 2230 UTC

24 May 2012:  DCLMA, SHAVE ops in NWS Sterling, VA (LWX) County Warning Area (CWA)

25 May 2012: OKLMA (maybe, on edge of 3d); 2300-0200 UTC

27 May 2012: DCLMA, 2340-0200 UTC

28 May 2012: OKLMA, 2200-0300 UTC

29 May 2012: DCLMA, 1820-2230 UTC; OKLMA, 1900-1130 UTC; NALMA (2330-0300 UTC); SHAVE ops in LWX and OUN CWAs.

30 May 2012:  WTLMA & OKLMA, 2100-0400 UTC. SHAVE ops in OUN CWA

31 May 2012:  NALMA likely. SHAVE ops planned over area. (edit, 5:35 CDT: FL-LDAR domain has had activity &  jumps today)

-K. Calhoun

PGLM Assists in Severe Thunderstorm Warning

Animation from 12 May 2011 covering from 2211-2226 UTC. The PGLM flash extent density is on the left with the corresponding radar reflectivity on the right. To see the animation, please click on the image.

Today’s afternoon shift started with forecasters working across the Norman, Tulsa, and Little Rock county warning areas.  With the some storms beginning to form south and east of Norman, Oklahoma, it was felt this would be a good opportunity to take another look at the PGLM flash extent density observations and focus on total lightning.  The PGLM flash extent density was very useful in identifying when the first cloud-to-ground strikes would occur.  The PGLM was preceeding the first cloud-to-ground strike by approximately 30 minutes today.

As the the afternoon progressed, the storms began to intensify, both on radar and with the PGLM flash extent density and we shifted from using the PGLM for lightning safety and moved into warning operations.  By 2211 UTC on 12 May 2011 (the first image of the loop shown above), three severe thunderstorm warnings were in effect.  The area of interest for this post is in between the two existing warnings in the west.  At 2211, the PGLM flash extent density was no more than a few flashes per minute.  By 2214 UTC the number of PGLM flashes was already approaching 40 per minute.  This continued to rapidly increase through 2220 UTC when the PGLM flash extent density observe 82 flashes in a 1 minute interval for a single 8×8 km grid box.  This was one of the largest lightning jumps of the day with an increase of 75 flashes per minute in a nine minute time span.  With this major lightning jump, along with the forecaster’s interrogation of radar data, a new severe thunderstorm warning was issued at 2226 UTC.  This warning was later verified with several severe hail reports.

Submitted by Geoffrey Stano, PGLM PI for week of 9-13 May.