Category: GLM

GLM and Lightning Cast

Posted in GLM, LightningCast, ProbSevere, SPG2022 on by Kevin Thiel.

The GLM parallax showed up again Thursday, June 16th, over the PBZ area. This was even more evident than yesterday’s event in WI that was written about in a blog post.  Figure 1 has ProbSevere, LightningCast, GLM Flash Extent Density, and ENTLN data overlaid in a 4-panel.  This case was fairly simple to “self correct” the parallax as the GLM was clearly displaced to the north of ProbSevere (as well as the base reflectivity).  Really once you get a few cases under your belt recognizing the parallax, it’s not too challenging to keep that “self correct” in the back of your mind.  One interesting thing to note about Figure 1 is the storm just outside the PBZ CWA just south of Mount Veron, Ohio (See bottom left in Figure 1).  The ProbSevere and GLM FED are lined up perfectly and this is a great example of utilizing the lower threshold in the colormap. The bullseye shows up much nicer than the larger thresholds in the top two images.

Figure 1: GLM with ProbSevere and LightningCast

– Podium

Observations from BUF on Thursday June 16th

Posted in DSS, GLM, LightningCast, Optical Flow Winds, SPG2022 on by Kevin Thiel.

Optical Flow Wind Storm Top Divergence Can Aid in Warning Operations

The storm of the day produced a 2.5” hail stone near Cato, NY.
Strong storm top divergence signals an intense or intensifying thunderstorm. Matched with upper level radar scans, satellite interrogation (clean IR), and ProbSevere, optical flow wind products may be another tool to aid the warning forecaster and/or storm scale mesoanalysis,  Below are the corresponding optical flow wind storm top divergence images approaching 4 PM EDT (3 PM CDT) when the sig severe hail was reported. The thunderstorm of interest is centered just south of eastern Lake Ontario.

LightningCast as Graphical Messaging/IDSS Tool

As the DSS and graphics person for BUF, I took the opportunity to highlight the utility of LightningCast for Graphical NowCasts and DSS graphics. The fairly broad brushed nature of the lightning probability contours at the timesteps utilized for graphics I think is a positive for a few reasons: they show actionable probabilities (10+, 25+, 50+, 75+) that users can understand; the contours are akin to annotations on a radar graphic, so would be a time saver; and finally, broad brushed is a way to prompt users and partners to seek out more information, like real time zoomed in radar data, perhaps calling or sending us a chat on NWSChat, or even simply keeping an eye on the sky and listening for thunder. The parallax corrected product in the images below I feel would be more useful for graphics of the nature shown below. Ultimately, for operational use, there would probably need to be some work done to ensure they are not confusing to the user and aesthetically pleasing.
Graphical NowCasts for our websites and social media
Graphic for IDSS Event

A Case for the Sharpened GLM FED Color Scale Used this Week

Over the course of satellite product interrogation this week, the GLM FED stood out as one of the most useful products.  Below are examples from in/near the BUF CWA at 2043z and 2047z. Note that the top of the color scale was set to 128 flashes/5 min over the grid point vs. the default 256 flashes/5 min in AWIPS. The FED also paired well with the MFA and TOE on this 4-pane procedure.
The color curve used this week really popped and correlated well with frequent ENTLN detections. Another example below from shortly after 6 PM EDT (2202 and 2207z)  shows that there will be instances where perhaps an even small color bar range would be useful.
While the strongest storm at this time still showed up well on the AWIPS default color bar range, the 128 flashes/5 min top end of the range (top right) helped it pop even more and corresponded well conceptually with the ENTLN cloud flash detections. Furthermore, the thunderstorms to the north of the strongest thunderstorm showed up better from an SA perspective, if you have been focusing on the strongest storm for warning ops. The smallest color bar range on the bottom left further enhances the above described effect.

Addendum: GLM Flashes and a more smoothed FED

The excellent COD NexLab Satellite and Radar page added within the past year the GLM flash centroids to their GOES derived overlays. From an apples to apples perspective with respect to the ground based lightning detection network displays, this may be a useful product to add into AWIPS.
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Addendum 2: Would a more smoothed FED be preferable?

Below are a few web based examples of FED displays.
A case can be made that these smoothed FED examples would be somewhat less obtrusive than the default AWIPS FED display, especially for storm scale interrogation by the warning operator or storm scale mesoanalyst.
– Hurricane84

GLM & Prob Severe in Low Radar Coverage

Posted in GLM, ProbSevere, SPG2022 on by Kevin Thiel.

With the Buffalo CWA being a long and narrow forecast area, there are areas where the Buffalo Radar doesn’t provide good coverage. On a day like today where their second radar (KTYX) isn’t providing any data, the entire eastern half of the CWA has the Buffalo radar hitting storms at 20 kft or higher. This meant that we had to more heavily rely on Satellite data for warning operations.

Looking at the northeast corner of the CWA we had convection popping for a few hours along a frontal boundary. Being able to look at spikes in the GLM over time and Prob Severe time scales and just instances in the Prob Severe were very helpful with determining what was going on in the lower levels that weren’t visible on radar. As one storm over the lake begins to move inland there is a jump in the GLM and Prob Severe.

Being able to see the upward trends in time with the prob severe over time and then the increasing GLM was a big confidence boost to put out a warning.

-Cirrus Fields

Which GLM Color Scale is Best?

Posted in GLM, SPG2022 on by Kevin Thiel.

One of the easiest ways to get an argument…I mean discussion…going among AWIPS users is color tables.

However, in this case it does pose an interesting thought experiment because the color table isn’t changing but the scaling is.  Case in point, look at a line of tornadic supercells across Wisconsin from the GOES East GLM:

Changing the range of the color table helps pull out some details with low flash rate storms.  Although the northern storms have some higher flash rates and can be seen when the scale is set to the default (260), the southern storms with a lower flash rate can pull out more details with the lower maximum point (60).

Others this week have come up with some great ideas; developing a climatology for FED to know what the best ranges would be for the display for a given season, event type, etc.  Another thing to look at is how to best develop a table for the logarithmic scale that is used with FED with a different or wider color range.

– Hank Pym

Pre-Convective Environment Across GRB

Posted in GLM, NUCAPS, Optical Flow Winds, ProbSevere, SPG2022 on by Kevin Thiel.

With a busy day still underway across Wisconsin, the use of the Optical Flow Winds, GLM, Prob Severe, and NUCAPS soundings were a big help in looking at the pre-convective storm environment and in warning operations.

When it came to looking at sounding data we had a NOAA-20, and AQUA pass for the polar orbiting satellites, that we could then compare to the special observed sounding from GRB.

There are some spatial differences in the locations since each satellite doesn’t pass over the exact location and the observed sounding came from the GRB office. I ended up grabbing NUCAPS soundings from west of the office where I thought the better storm environment would be. Regardless of this they do show great information over a temporal and spatial scale.
Just between Aqua (bottom image) and NOAA-20 (middle image) you can see that the environment becomes much more moist over time (AQUA came around 19Z and NOAA-20 came around 18Z). The increase in temperatures and dew points in the low levels between the two NUCAPS soundings show that there was increasing low level lapse rates and increasing CAPE through time. Then compare both of these to the special sounding sent out by GRB, you can see AQUAs vast improvement in the low level over NOAA-20. The one caveat seems to be the smoothing of the values in the mid levels. Smoothing seems to have decreased the values almost too much for both satellite soundings. It is fairly within reason given that there is a dry layer in the mid levels on the observed, but the smoothing looks to have slightly overdone it.
Moving on to the GLM, it was very helpful when boosting confidence in the warning operations. There were lightning spikes collocated with increasing rotation and reflectivity. The one things worth mentioning is to have a reminder or maybe even have offices lower/change the color curves for FED prior to the start of an event. It could even be a permanent change that some offices make.
Since I was the only one in the group to check, compare, and lower the FED color curve accordingly it was much easier to pick out lightning jumps. From the graphic above alone, 0-65 was much more informative than 0-128 or 0-260.
The last thing worth mentioning for the day was the Optical Flow Winds. While this was helpful in a warning environment to look at storm top divergence and speed of the winds at the tops of clouds, I was able to find another great use for it. In the pre convective environment I had pulled up the Optical Flow Winds and noticed that it was tracking winds and speeds of clouds over Lake Michigan. In an area where any wind information and observation data can be very sparse to near non-existent. The optical flow winds could be very helpful for open waters forecasting.
-Cirrus Fields

GLM Parallax and Lightning Cast Fun

Posted in DSS, GLM, LightningCast, SPG2022 on by Kevin Thiel.

The GLM data, specifically the FED data, was used to provide DSS to the Riverfest in La Crosse, WI.  After my first contact with the event POC, I noticed that the FED data was off by roughly a county from the ground-based lightning data.  This was my first time witnessing the parallax issue from the GLM and why ground-based lightning networks are a key component in confirming that the GLM location is accurate. In Figure 1, notice the intense concentration of the lightning just southwest of the event (20 mile and 5 mile radius rings) depicted by the GLM while the ENTLN/NLDN say that concentration is about a county south.   The parallax is evident in other lightning concentrations in and around the event circle.  I know it’s something being worked on to have the GLM data corrected to avoid this parallax issue, but it would be nice to have a map of the locations where the parallax is more evident in case you may not need the corrected version. Obviously, the further north, the larger the parallax, but not quite sure at what latitudes it really starts to show its hand. On a side note, for aviation purposes, the parallax could become problematic if the GLM lightning data is off by a factor of a county or two, especially if re-routing aircraft is occurring.

Figure 1: GLM Flash Extent Density compared with ENTLN data on June 15, 2022.

Figure 2: FED and ENTLN animation showing the GLM parallax.

I utilized the Lightning Cast to provide a probable end time of the lightning threat for the Riverfest event in La Crosse, WI.  This was a valuable tool as it provided some added confidence when the storms would exit the event area.  I did my best to line up the TOA tool with the 25 percentile contour. Once I got my estimated time that the end of the lightning threat would reach the event, then I added about 30 minutes to ensure it was well east of the event circle.

– PODIUM

GLM and ProbSevere – Day 2

Posted in DSS, GLM, SPG2022 on by Kevin Thiel.

Utilizing the GLM data for DSS and severe weather operations is vital in providing timely and quality information to our partners and the public.  In this instance on Tuesday, June 14, 2022, we were monitoring storms near a DSS event (baseball tournament) located in Panama City Beach, FL.  You can see the location marked as Home on the following animations.  Two main forecast concerns, isolated convection along the beach due to the sea breeze and a line of storms moving south west out of SE Georgia into northern Florida heading toward the DSS event.

The first, and most imminent concern, was focused on the isolated storms developing along the sea breeze front throughout the FL Panhandle. The main threat with these isolated storms was lightning and brief heavy rain.  Utilizing Day Cloud Phase Distinction RGB overlaid with GLM Flash Extent Density, Minimum Flash Area, and Total Optical Energy was used for the DSS provided.  A line of CU developed to the east of the event moving westward.  Again, the main concern was with lightning but certainly with the amount of instability (DCAPE present), downbursts could pose a threat as well.   Utilizing the GLM data, they were able to contact the event POC to notify them of the lightning threat to the east and if held together could reach the 10 mile radius within next 1-2 hours (21-22z).  What helped with the lightning briefing was the short intensity shown on the TOE and MFA within that storm to the east of Home. It quickly weakened and we were able to notify the event coordinator of this information providing them with further confidence to not have to evacuate their facility during the tournament.

The second concern for the event was the line of storms to the northeast in GA/northern FL moving southwest toward the event.  The great news about this storm was the very very slow movement southwest.  Thus, the threat of lightning and gusty winds would hold off for a considerable time frame.

– Podium

LightningCast/NUCAPS and Isolated to Scattered Convection in FGF

Posted in GLM, LightningCast, NUCAPS, SPG2022 on by Kevin Thiel.

Convection developed rapidly to the south of the main area of convection in an area of high instability. This was first picked up by higher probabilities in the LightningCast data. There was some rapid cumulus development that was picked up well by the algorithm. Probabilities went well above 75% around 5 minutes or so from the first GLM detection. NUCAPs data indicated MLCAPEs of around 2000 J/Kg in this area supporting the quick upscale growth.

Convection developed rapidly to the south of the main area of convection in an area of high instability. This was first picked up by higher probabilities in the LightningCast data. There was some rapid cumulus development that was picked up well by the algorithm. Probabilities went well above 75% around 5 minutes or so from the first GLM detection. NUCAPs data indicated MLCAPEs of around 2000 J/Kg in this area supporting the quick upscale growth.

LightningCast and GLM at 2131 UTC

DCP RGB and LightningCast  2131 UTC

MRMS -10 Reflectivity and LightningCast first GLM detection at 2135 UTC

So let’s take a look at some NUCAPS soundings as we had three overpasses right before the convection initiated in the above examples.  Here is the first overpass with the sounding point selected with the red arrow:

NUCAPS Sounding at 1823 Z

Not too shabby with a MLCAPE value of 2094 J/kg.  (And why mixed-layer? Hank likes ML because very few times do parcels start at the surface for SB, and MUCAPE is just fun to look at).

The next overpass was 2003 UTC (about an hour and a half after the previous overpass) to see if the environment has changed much:

MLCAPE of 1235.  Hmmmm…that’s quite a drop in MLCAPE compared to previous overpass.  Two things to remember; this is on the edge of the field-of-view (matter of fact, the eastern edge).  Luckily we have a Modified NUCAPS for the same profile point which adjusts the boundary layer:

Yeah, that looks much more reasonable based on observational trends (few clouds to change the mid-atmospheric profile, increasing surface T/Td conditions) with 2185 J/kg MLCAPE.  But wait, there’s more!  We also have a:

NUCAPS AQUA Overpass

This was almost directly under NADIR so we should have much better profile retrieval.  Sure enough, MLCAPE value is almost 3000 J/kg in between the 1823 and 2003 UTC NOAA-20 sounding retrievals.

How does this all tie into the weather for FGF today?  This is what the SPC Mesoanalysis graphics had for 2100 UTC MLCAPE values:

They all combine to increase confidence on what conditions COULD be in areas where the models are saying one thing and an observational system is indicating potential reality (remember, it’s still a remote sensing platform with their own set of issues). In our case, the bulls-eye of 3000 J/kg in east central Minnesota is likely real and needs to be an area to watch…and that is where the Lightning Cast product at the start of our post indicated the potential for new activity to develop.  Pretty cool stuff…

– Marty McFly/Hank Pym

Where is the new convection going up?

Posted in GLM, LightningCast, SPG2022 on by Kevin Thiel.

The GLM can be used to help find where new convection is developing under a cirrus canopy.  Here’s an example of this!

Top left – LightningCast with Day Land Cloud Convection and Flash Extent Density (FED).  Top Right is Minimum Flash Area (MFA). Bottom left is MRMS 1km Reflectivity.

We can see that there are some returns developing in the center of the field of view on the MRMS reflectivity but it is hard to tell whether this is real or not.  Five minutes later, we have this image:

Hmm, that could be new convection developing on the Top Left panel because it looks like there is a tower coming through the cirrus shield.

And then the next frame we have:

And there we go!  Flashes starting to show up so it looks like this area of convection will need to be watched.  (Should also note that it would also be helpful to time match to the GLM 1-minute FED instead of the 5-minute RGB!)

-Hank Pym