Category: GLM
GLM & Prob Severe in Low Radar Coverage
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
A case for NOT changing the GLM image range
Storms going up across NY State have been trending upward with time. So much so that we’ve gone beyond both the 65 and 130 flash/5 min rates:
179 flashes/5 minute north of Syracuse. That’s pretty impressive! And it’s been trending upwards so the lower left pane with the image scale up to 65 has been blown out for multiple frames.
– Pym
Which GLM Color Scale is Best?
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
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.
GLM Parallax and Lightning Cast Fun
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
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
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?
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
Metwatch for Wilmington DSS event
Metwatch for Wilmington NC started with modified NUCAPS soundings and a comparison with NAM BUFKIT profiles:
Looking at 700mb temperatures, BUFKIT has about 8C for that layer, and here is the gridded NUCAPS 700mb temperature layer. Note: not a lot of advection noted at 700mb, with low level dry advection (not shown)
Watching this cell just outside the CWA pulse and then fall apart…PWV3 never exceeds 4% with this pulse. LightingCast also showed a rapid drop in probabilities.
Not much happened today, but just along the coast was this little area of enhanced CAPE (3000j/kg)…so you’re saying there’s a chance…
Comparison between parallax corrected and uncorrected lightning cast. You can see the image above and to the right (corrected) has some higher percentages getting into the 20 mi range ring compared to the non corrected data which just has the 25% grazing the 20 mi range ring. Having the corrected data could be more beneficial to providing DSS support.
– Mr. Bean
– Noctilucent