GLM parallax issues?

We've been watching t-storms across central/southern SD and northeast ND today. A few storms were severe with reports of hail 1" or greater. I was kind of
expecting to see some GLM FED lightning jumps with these storms as they became severe, but that just wasn't the case.

Could this be a parallax issue?

This far N (roughly a similar latitude to Toronto, only farther W, so that there are even MORE potential parallax problems), the GLM is likely not sampling storms very well (at more of a side angle), so perhaps it can't actually "see" all of the lightning occurring within a storm.

If that is the case, watching for lightning jumps within a storm might not be a good "warning determination method" for a forecaster across the Northern High Plains and Northern Mississippi Valley...

Or...

Maybe we can still see lightning jumps in more northern/western storms, but due to parallax, we should expect more storms to have lower lightning values, hence lower lightning jump thresholds?

Other parallax-related questions I have include:

How does parallax affect other GLM products like the Total Energy and Avg Flash/Group Areas?

If the GLM is sampling more of the side of a storm across the northern US, can we expect storms to look brighter or darker?

Should we expect the areal extent of lightning flashes within a storm appear to increase or decrease as parallax increases?

How parallax affects GLM data is a mystery to me at this point and certainly another area of research that GLM developers should explore.

- Thomas Bell

DLH - GFS CAPE forecast degrading all-sky CAPE

During my mesoscale discussion I blogged about how the all-sky CAPE did not seem to match up well at all compared to SPC mesoanalysis. I compared the all-sky CAPE to the clear-sky only CAPE & noticed that the most questionable areas were blacked out on the clear-sky product, & thus filled in with GFS data. Looking at the 12Z GFS CAPE data it was obviously too high with 2500 J/kg SBCAPE over NW MN & over 3000 J/kg over SE MN. It took me a while to identify that the GFS CAPE was too high & thus the all-sky LAP CAPE would also be too high because I really do not use the GFS much when doing a short-term mesoscale analysis. I think it would be much more useful to fill in the missing clear-sky data with RAP/HRRR/or some other hourly updating field vs the every 6-hour GFS.

22Z LAP all-sky CAPE:

22Z clear-sky CAPE:

Peter Sunday

Highest Flash Event Densities Collocated With Updraft Location

[23:00 UTC] Have tried to overlay semi-transparent GLM data over GOES-East meso-sector visible imagery and the results are pretty useful. For one, the highest flash event densities seem to be collocated well with perceived updraft location (overshooting tops are being used as a proxy), which fits the conceptual model of what one would expect. It should be noted that the values themselves were not quite as useful as seeing the change in the values and the "peaks" in values which were highlighted a bit more by altering the color scale. This certainly is useful in an operational setting in terms of isolating the most important (rapidly developing) updrafts in a quick and timely fashion.

Fig. 1: GLM FED data overlaid on GOES-East meso-sector Ch. 2 data

Rosie Red

CI With Radar

Couldn't tell if there was something weird with the CI probs...it looked like the storms had already developed.  Unless it picked up that more towering CU was developing right next to the new storms.  Which in this case it seems possible as the storms were building off each other and morphing into a line.

-Penny Gardens

*Later note. I tried using this to overlap outflow boundaries with the CI or CI Severe to see if any CU developed along the boundary.  Didn't see anything, but that may be because of the cirrus.
And is there a probability tool for a gust front? I'm always reminded of the Indiana State Fair situation.  I kept seeing gust fronts ahead of our storms today...however the peak wind seemed to be only about 30 mph.  

GLM Average Flash Area - Updraft vs. Non-updraft/Anvil

[22:00 UTC] After an idea was shared with me from a colleague of mine of increasing the transparency of GLM data, I decided to explore its usability overlaid on visible satellite.

More specifically, I took a look at average flash area to see if there was any notable difference between the perceived updraft and anvil areas of mature convection moving through the Duluth CWA.

While data still remains a bit jumpy, I did notice that it seems that the average flash area near the overshooting tops (used here as a proxy for approximate updraft location) seems to be lower/smaller than in surrounding anvil areas or in areas where updrafts do not appear quite as strong (or have become weaker). The average flash area appears to increase as the convection becomes "older" (i.e. new/strengthening updrafts not apparently seen on visible imagery). Fig. 1 shows an animation through time while Fig. 2 shows a still frame at 21:40 UTC.

Fig. 1: animation of 5-min/1-min GLM Average Flash Area overlaid on GOES-East Ch. 2

Fig. 2: still of 5-min/1-min GLM Average Flash Area overlaid on GOES-East Ch. 2 at 21:40 UTC

Rosie Red

DLH - Nifty Convection Monitoring Procedure

2150Z: I decided to try looking at smoothed GLM data overlaid on visible satellite by using the "interpolate image" & "interpolate colors" options along with some transparency in AWIPS. On the same image I also overlaid ProbSevere polygons & GOES CI probabilities. It was much easier for me to interpret GLM trends while having some of the texture from the visible satellite imagery. The identification of new updraft growth in the GLM flash extent density data was much more evident with this procedure vs just using the GLM data alone. ProbSevere polygons were useful in monitoring the intensity trends of the storm at a glance. Finally having the GOES CI probability helped in a zoomed-out view to identify potential area of new convection. I'm impressed at the amount of data I'm able to view in this procedure without the whole thing looking too cluttered.

Loop of above procedure showing storm evolution in SW MN:

Peter Sunday

T-storm Warning Decision Process

The storms are heading into a more prime environment based on what I've been looking at (see earlier blogs).  

The ProbSevere increased with each scan leading up to the warning.  The lightning slighly increased.  There were so many cells that it was a tad confusing which one was strongest. The flash centriod density helped a bit...it's a nice small scale with the pixels that I overlapped with the storm.
-Penny Gardens


*Side note the t-storm warnings verified with storm reports from NWS.

000
NWUS53 KFSD 242246
LSRFSD

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE SIOUX FALLS SD
546 PM CDT THU MAY 24 2018

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0522 PM     HAIL             3 W SCOTLAND            43.15N 97.78W
05/24/2018  E1.00 INCH       BON HOMME          SD   PUBLIC 

 000
NWUS53 KFSD 242216
LSRFSD

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE SIOUX FALLS SD
516 PM CDT THU MAY 24 2018

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0502 PM     HAIL             6 S DANTE               42.95N 98.19W
05/24/2018  E1.25 INCH       CHARLES MIX        SD   PUBLIC           

            HAIL COVERED THE GROUND. 

Parallax Issues: Beware in the Northern Plains and Northern Mississippi Valley regions!

Just looked at a cluster of showers/storms in southwest MN and noticed that the IR satellite image and GLM data are offset (to the north) from MRMS "reflectivity at lowest altitude" radar data by as much as a county!

This parallax issue is something that WFOs and CWSUs across the Northern Plains and Northern Mississippi Valley regions will certainly need to be aware of when they use GOES-16 data, as it may lead them to issue warnings/advisories for the wrong storms!

- Thomas Bell

DLH - Mesoscale Discussion

2100Z: Storms have been ongoing for a while across the region but waited to write this post until the modified NUCAPS soundings were in. Right off the bat the all-sky CAPE does not seem to capture the general spatial pattern well compared to SPC mesonalysis/HRRR & observations. The all-sky suggests CAPE over 1000 J/kg over NW MN & SE MN & along a narrow tongue from southern MN up towards the Twin Cities. However mesoanalysis shows CAPE minima in these areas along with high CIN. Furthermore the all-sky LAP CAPE does not seem to capture the extent of the stable capped region in NE MN where storms have struggled in so far today.
2030Z LAP all-sky CAPE:

2000Z MLCAPE Mesoanlysis:

Furthermore visible satellite shows little cu development in the regions of suggested highest instability in NW & SE MN, with minimal GOES CI probabilities as well. 
2030 Visible Satellite/CI probablities:

Gridded NUCAPS 500-700 mb lapse rates match up quite well with mesoanalysis with rather marginal values of 6-6.5 C/km across most of MN. However, NUCAPS does not appear to pick up on the EML moving up from SD up into SW MN where mesoanalysis as well as the HRRR/GFS/NAM all suggest values greater than 7 C/km.
NUCAPS/HRRR/GFS/NAM 500-700 mb lapse rates:

 Overall, the thermodynamic environment does not have me too concerned about widespread severe weather today. Effective bulk shear values of 30-40 kts suggests some organization is possible & it will be interesting to see if the current cells eventually merge into a line as the HRRR suggests, and create more of a damaging wind threat. Some cells have spiked up at times this afternoon with ProbHail & ProbWind values over 80% but otherwise have not been able to maintain this intensity.

Peter Sunday

RGBs

I looked at the Day Cloud Distinction RGB with the Severe CI overlapped.  This was a nice tool to see how the storms were evolving along with where I needed to look for severe cu developing.  Again, the values on this were very low in the next 0-2 hours.  Only saw 1% for severe.

I overlayed the Severe CI over water vapor RBG.

The CI showed 30+% just before changing to an actual towering CU indicated by the water vapor image.  Severe CI was 1%. 

-Penny Gardens

Duluth MN 21 UTC Mesoscale Discussion - NUCAPS

[21:00 UTC] Convection has been ongoing across western and southern portions of the Duluth MN for several hours now during peak diurnal heating. Activity continues to track northeast through the area in an environment characterized by sufficient instability with SBCAPE between 1500-2000 j/kg, as depicted by SPC mesoanalysis. NUCAPS soundings showed a slightly more unstable environment with SBCAPE of nearly 2500 j/kg, but NUCAPS sounding Sfc LI, PWAT, and SBLCLs were generally in fairly good agreement with the traditionally-used SPC mesoanalysis. SB CAPE and LI would suggest that convective activity will maintain itself through the next several hours before it gradually enters a more unfavorable/unsupportive environment across the northeast after approximately 23:00 UTC or so. It should also be noted that there appears to be a non-zero tornado threat as SB LCLs are fairly low and surface backing remains fairly pronounced. Although speed shear is not particularly strong and/or robust, the low level directional shear will likely allow for some rotations within updrafts that move through this area. Best chances will exist across north/west parts of the local area. Will continue to monitor development and evolution for possible warning issuance.

It should be noted that having the ability to "point-and-click" to retrieve a sensed sounding in an area of interest is extremely useful. There is always a bit of QC that goes into any data/situation analysis, but to be able to see a sensed sounding in an area that otherwise would not have such data would be very beneficial in an operational setting.

Rosie Red

DLH - Warning Issued based on ProbSevere

2030Z: I issued a warning on a storm near Hill City, MN primairly based on data from ProbSevere. I was started watching the storm when ProbWind values got above 70%. The storm was in a solid environment & GLM data as well as cloud top cooling trends from IR indicated the storm was steadily maintaining its intensity.  Once ProbWind values showed an increase to 80% & MESH values continued to increase over 1" I decided to issue a SVR for 60 mph wind & 1.5" hail. Shortly after issuing ProbHail & ProbWind both continued to increase & MESH increased up to 1.22"

What I found interesting was that the storm to its north seemed to look stronger with higher values of GLM flash extent density & total power, as well as higher reflectivity values. However, ProbSevere values were much lower with this storm with ProbWind the only field of interest up around 58%.

GLM 4 panel animation:

MRMS RALA/warning animation:

Peter Sunday

CI Probability: Some questions (and another potential use)

We've evaluated CI Probability products this week, with some mixed results, but that has me thinking (which, as my wife will attest, is usually not a good thing)...

Have CI developers noted any correlations between the % shown and how quickly cells with reflectivity values > 35 dBZ develop?

One of my co-evaluators noted a small area of 90% CI Prob yesterday and within a few minutes, a strong cell developed.

I have observed several areas where there were consecutive CI Prob % in the 40-70 range within which convective cells developed, but that process took a little longer, closer to 20-35 mins.

It may seem intuitive that a 90% CI Prob area would generate convective cells quicker than an area where the CI Prob potential is in the 40-70% range, but is this really the case? Maybe this is one use for the CI Prob product that could/should be explored further.

And, how long does an area need to be highlighted with a decent (50%) CI Prob before a forecaster should be confident enough in the development of a cell with reflectivity values > 35 dBZ? Our evaluation group hasn't been able to answer that question during this week of testing.

- Thomas Bell

GLM, Flash Centriod Density

I used the flash centriod density over the radar to pinpoint quickly where the strongest storms were located in a shield of cloud cover.  GLM data on the other screens were increasing a bit too. This area is capped for now.  But models have the CAPE growing and the CAP breaking in a few hours...so we have time before these storms may become severe in a better environment.

-Penny Gardens

NUCAPS Comparison

I was curious to see differences in the Improved Latency vs. Modified soundings.

IL sounding has CAPE 707   CIN-53
Actual meso matched up.

Here is the Modified sounding.  CAPE 707 CIN -53  Everything matched up when I checked K index, PW, LCL.

I looked at other soundings comparing the IL and modified and I found they matched up well.  But I decided to look at the modified soundings to be sure.

I also used a couple of the procedures with NUCAPS overlayed with the LI.  This was a good comparison to see where I needed to focus in on vs. where the green soundings were. 

-Penny Gardens

Sioux Falls, SD Discussion

Looking at the environment prior to convection.  Sioux Falls has a slight risk for the western half of the WFO area.
All Sky CAPE shows high values of 1000-2500 j/kg.  Compared to the Mesoscale on SPC it's 4500 j/kg or higher.  Ignoring the values, you can see the upward trend of increasing CAPE on All SKY.

All layer PW on All SKY shows lots of moisture available 1.2 to 1.7!   It is more detailed where the highest values are located. 

PW values of 1.2 to 1.3  on the mesoanalysis.



-Penny Gardens

AllSkyLAP LPW with Differential Water Vapor RGB

I'm trying a 4-panel with AllSkyLAP Sfc-900mb LPW (top left), AllSkyLAP 900-700mb LPW (top right), AllSkyLAP 700-300mb LPW (bottom left) and the Differential Water Vapor RGB product (bottom right).

Note the differences in the bottom two images over the eastern Dakotas. There are some mid-level clouds showing up on the Differential Water Vapor image, obscuring the view. Is there a layer of dry air below those higher clouds? The AllSkyLAP 700-300mb LPW product seems to think so. I'm not sure if this due to the model background being used under the thicker clouds or if the cloud retrieval process is working its magic and is accurate. It would really be nice to get some sort of "ground truth" to determine how accurate the AllSkyLAP 700-300mb LPW product really is in this area. The same could also be said across northeast MT and northwest ND, but one can actually see that the model background is being used there. It is harder to make that determination  across the eastern Dakotas.

It may actually be beneficial if the model background in AllSkyLAP products stood out a little better to highlight "use data with caution" areas for forecasters. Otherwise, because of the blending being done, a busy forecaster might mistake these areas for real, satellite-observed data.

- Thomas Bell

MRMS Reflectivity at -10 C vs. First GLM Flash Centroid vs ENTLN

[19:30 UTC] Convection is well underway in the upper midwest as of this writing with activity beginning to overspread western and southern portions of the Duluth CWA. Decided to take a look at MRMS reflectivity at the -10C isotherm (which is often used as a proxy for initiation of electrification within a developing shower/storm). Although not always the case, previous studies have suggested that the -10C reflectivity of 35 dBZ can be used as a threshold for there to be lightning present within a cell. Certainly there is probably a range that could also be used as a proxy, but for these purposes decided to look for 35+ dBZ on MRMS at the -10C isotherm.

For the developing cell of interest, the first 35+ dBZ on the -10C isotherm appeared at 1830 UTC. 4 minutes later, the first GLM Flash Centroid was noticed with the cell and the first flash event density also appeared. Decided to take a look at the ENTLN ground-based detection as well, and as it turned out, the first cloud flash was detected at the same time the first GLM flash centroid appeared.

 

 Fig. 1: MRMS Reflectivity at -10C isotherm at 18:30 UTC

Fig. 2: MRMS Reflectivity at -10C isotherm at 18:34 UTC

 

Fig. 3: GLM First Flash Centroid Density at 18:34 UTC

 Fig. 4: ENTLN First Cloud Flash Lightning Plot at 18:34 UTC

Rosie Red

GLM first identified developing storm in WI

1923Z: Weak storms continue to develop across MN & WI in the absence of any major forcing feature & marginal instability. While we're acting as WFO DLH I noticed an area of increasing GLM fields in central WI shortly before 1900Z where otherwise no other convection was ongoing. While there is an 8 minute gap in the 1-minute satellite data from 1858-1906Z the IR values really didn't begin to pique my interest until 1910-1915Z. Also, a noticeable increasing lightning trend with ENTLN data wasn't really noticed until 1905-1910Z as well so GLM was able to capture the initial electrification of this storm with few minutes extra lead time. On a day like today when monitoring areas of cumulus for the first convective echoes to develop, GLM (especially GLM total energy) was especially useful.

Peter Sunday

AllSkyLAP Layer Showalter Index: First Impressions

A first look at the AllSkyLAP Showalter Index (SI) product and comparison with the SPC Mesoscale Analysis SI product yields a few observations/thoughts.

1. The color scale seems inverted to me. The negative SI values should grab one's attention, so perhaps they should be in the brighter (yellow/orange/red) colors?

2. Until GOES-17/GOES West comes online, I would use this product (and all AllSkyLAP products) with a lot of caution over the west due to parallax and lack of data. We can see some of this in the NW corner of the first image below.

3. The AllSkyLAP SI again has areas across the central and northern Plains (NE-SD-S MN) that are significantly different (greater negative values) than what is displayed on SPC's SI product at approximately the same time, especially across SD/S MN. However, it actually captured gradients across IA and MO pretty well...and values there were similar to what are shown on SPC's SI product.

4. Certainly be aware of where there are clouds/precip, as SI values will not match SPC's SI product values. This is the case in the image below across northeast MT/northwest SD and northern/cntrl MN.

- Thomas Bell

AllSkyLAP Layer K Index: First Impressions

Decided to take a look at the 1758Z AllSkyLAP Layer K Index (KI) image and compare it to the 1800Z KI product on SPC's Mesoscale Analysis Page. At first, I liked the AllSkyLAP Layer KI color scheme, but the more I look at it, the more I don't like it. It seems like higher values should be those areas in red (to highlight the highest values for severe wx potential considerations), but that is not the case.

Areas where there are clouds/precip (such as northeast MT/NW ND, cntrl MN and over the mtns of northern CO) have lower KI values, probably because of the model background being used.

Elsewhere, such as across central/northeast NE and southeast SD, where there are high values on the AllSkyLAP Layer KI image, these values are actually higher than what the K Index product shows on SPC's Mesoscale Analysis Page.

Outside of the aforementioned areas where the model is probably the background, the AllSkyLAP Layer KI image does show high and low KI "areas" and gradients similar to the KI product on SPC's Mesoscale Analysis site.

- Thomas Bell

Day 4 Operations

Today we will once again be operating well north in the Duluth, MN and Sioux Falls, SD CWAs.

-Michael

Week 4 Day 3 Wrap Up

Feedback comments from operations yesterday in the northern high plains is posted below:

NUCAPS

Only used the modified version

Modified version was quite a bit better than the unmodified most of the time

There seemed to be a lot of conflicting information between some of the fields and some of the
other operational tools used to assess the environment

Use with caution where there are clouds as the NUCAPS seem to struggle with areas of clouds
sometimes

In the dry areas, the theta-e values matched up pretty well

The modified soundings seemed to match up better with the environment and seemed to have much
more value in an operational sense

Having the gridded data filled in was better to be able to visualize the gradients easier than having to
interpolate through the gaps

Using the gridded data with the sounding points overlaid is helpful to understand where there might be
bad data

Adding some type of wind data would be helpful as well, possibly from GOES or other kinds of
observations

All-Sky LAP

Mostly used the CAPE fields and somewhat used the PWAT fields to look at moisture transport

Noticed a little bit of a dry intrusion into southern SD on the low level PW field where a storm
eventually developed

CAPE was very low yesterday, again using the RAP would probably provide better data, especially
in the CAPE field

Again used more for awareness of where relative higher values are and not looking so much at what
those values are

Helpful for showing where the drier air was in the layered PW product

Is still very nice to have the all-sky as opposed to the clear sky, it’s easier to ignore the lesser quality
data than trying to fill in on your own

ProbSevere

ProbSevere struggled a bit on the storms in Billings as opposed to looking at some of the other data

Can’t be used in a vacuum

Environment was not very good yesterday which seemed to throw off ProbSevere somewhat

Knowing the environment is very important to using ProbSevere and judging the future potential of the
storm

GLM

Getting more use is proving to provide more comfortable using the different products

Trends seemed to show up a little better in the Total Energy product yesterday rather than the FED

Training should probably address the different types of environments and how GLM can fluctuate
depending on area and environment

Detection efficiency seems to fluctuate depending on where you are in the country

Used GLM data a little bit in an aviation sense yesterday to compare with SIGMETs and other aviation
advisories

Also looked at the data over the ocean to see if there were storms off the coast away from any radar
coverage

Used the flash area along with total energy to try to pick out areas of new growth where flash areas
would theoretically be smaller

Tried to compare with Earth Networks data to see if there were different types of lightning in the storms
and how that related to the trends in the Event Density

The areal extent would be important to show to the public or something via social media or other
networks

The event density seems to show the storms intensifying, or the lightning ramping up, prior to the FED

CI

There was never really a threat for initiation in Rapid City

It was picking some stuff up under thin cirrus, they were very low values, but it did pick up some on
the cloud features

Severe values seemed to stay pretty low in the area

The CI did seem to pick up some higher values on storms that initiated south of the Billings area

Did pick up on some areas of initiation out of the Rapid City area that were areas of interest

Yesterday seemed to work pretty well and was good at focusing attention on areas of interest

Other

The cloud top products are difficult to use in convection due to the blockiness and non gradients in
the color scale

UNR - GLM/ENTLN lighnting data on a severe storm in SD

ProbSevere indicated a severe thunderstorm that explosively developed along the SD/NE border. This storm initiated in a favorable environment & I anticipated it to further develop, so the rapidly increasing values in the ProbSevere values along with an increase in CG activity from the ENTLN were plenty for me to feel confident in issuing a warning for 2" hail.20 minutes after my warning, ProbHail had increased to 99% with a MESH value of 2.25".

For comparison, I looked at the GLM data along with observed lightning data from the ENTLN. The ENTLN showed an obvious increase in CG activity beginning around ~0015Z from the ENTLN data. However, there never was an obvious increase in GLM flash extent density or total energy.

GLM/ENTLN loop:

Peter Sunday

Rotation vs lightning trends

On a severe t-storm there's some rotation that keeps showing up.  Here are some images as the lightning changed during the scans.  I would issue a tornado warning.
-Penny Gardens

Using GLM data over the Atlantic Ocean

Over the Atlantic Ocean, GLM data will eliminate much of the guesswork in determining what is and what is not a thunderstorm. Not only will this help the aviation community, but it will help the Navy as well as shipping, fishing, marine, recreational boating and cruise liner communities, to name a few.

In the example below, I have paired the GLM FED with GOES-16 Ch 13 imagery. It is very apparent that the colder cloud tops are, indeed, associated with thunderstorms.

- Thomas Bell

GLM Data on Rapidly Developing Storm

[00:30 UTC] Storms continue to maintain (if not increase) their strength as their pivot north and northeast through the Billings CWA. Of particular interest is the rapid increase in GLM flash extent density collocated with smaller average flash area and high total energy with a quickly-developing and strengthening updraft. The increase in flash event density also aided in the decision to put out a warning for the storm (particularly given the environment), even as ProbSevere values were below 50% (but increasing). With just ProbSevere or just GLM, or just CTT data to look at, confidence would be lower than when taking in all of the datasets together.

Fig. 1: Flash extent density, average flash area, high total energy, and IR for rapidly developing thunderstorms.

Fig. 2: Cloud top temperatures cooling near location of updraft.

Rosie Red

GOES Cloud Top Pressure vs Ch 13 IR

I'm not sure that I'm a big fan of the Cloud Top Pressure product for a few reasons:

1. It is too blocky/choppy, which makes it very difficult to use for a smaller, WFO-sized area. Certainly in the example below, the Ch 13 IR imagery has a much finer resolution, allowing a forecaster to more easily find/track convective cloud tops and their trends.

2. The default color scale makes it very difficult to determine where the higher/lower cloud top pressure values are. The blue to light purple transition above 300mb is too subtle, so convective cloud tops are not easy to find.

3. It doesn't seem to do a good job distinguishing cloud top pressures of thin cirrus, as we see below in areas east of the big convection.

Compare the GOES Cloud Top Pressure (top left) and GOES-16 Ch 13 IR (top right):

- Thomas Bell

GLM data benefit for aviation forecasting

As GLM data become readily available in AWIPS-II, they will be very useful for aviation forecasters who are certainly interested in the severity of t-storms, but more immediately are interested in knowing that a convective cell IS a thunderstorm for the purposes of issuing an advisory and routing aircraft around the convective cell. GLM data will help aviation forecasters answer the question "Is that convective cell a thunderstorm?" earlier than just relying on the presence of CG strikes and will provide lead-time on CG strikes. In more than one instance this week, GLM has provided 5-10 min of lead time on the first cloud CG lightning strike in a convective cell. Such lead time and the knowledge that a convective cell IS a thunderstorm will prove invaluable to the aviation community.

- Thomas Bell

UNR - Large discrepency between ProbSevere CAPE & all-sky CAPE

2340Z: Prob severe is showing two likely severe storms with ProbHail greater than 90% across SW SD & W NE. The northern storm is in an environment of ~1000 J/kg MLCAPE & the southern one near Scottsbluff, NE ~2100 J/kg based on values from ProbSevere. The all-sky CAPE product was very low compared to ProbSevere only suggesting 300-400 J/kg CAPE with the northern storm & 500-600 J/kg with southern one. The strength in the all-sky product is with identifying spatial patterns & temporal trends in instability, but i find it really hard to trust in this event with values that low.

2316Z ProbSevere/MRMS RALA:

23Z LAP all-sky CAPE:

Peter Sunday

Flash Centroid Density

Watching developing storms, I used the GLM data over Level 2. It was helpful to see the peak flash centroid density spikes.  The increased values coincided with the increased 28 fl/min.

I issued a severe t-storm warning and as soon as I did the MESH increased along with the ProbSevere for hail. Flash per minute jumped to over 50.

I see the Flash Extent Density spiked just before I issued my warning.

*Addition...the NWS never warned this storm.  But the GLM just screamed that the storm was instesne and the ProbSevere levels were pretty high.

-Penny Gardens

UNR - Warning isssued for storm moving into SW SD. ProbSevere.

2310Z: After a lengthy internal struggle I decided to issue a SVR on a strong storm moving from NW NE into SW SD (2206Z issuance time). Primary reason for issuing was ProbHail which had values of 92% & as MESH of 1.62" right before the storm crossed into the CWA and a warning decision had to be made. This storm had rapidly intensified in the prior 20 minutes with a drastic increase in ProbSevere & MESH values & was moving into the area of our CWA I was most concerned about for severe weather this evening.

However I had reservations based on the near-storm environment the storm was moving into from SPC Mesoanalysis, which showed mixed-layer capping still in place. Furthermore the all-sky CAPE showed very low values less than 500 J/kg across SW SD & NW NE. Initially I dismissed this product as having values unrealistically low but I did notice an increasing rend in CAPE advecting into our CWA. Based off of a conventional near-storm environment analysis I was not a fan of the environment the storm was moving into but it's really hard to ignore a storm with ProbHail > 90% & MESH > 1.5 moving into your CWA, while under a severe thunderstorm watch, with satellite data showing an increasing trend in instability. Looking back at the storm after the fact, the MRMS reflectivity at -20C & 50 dBZ height were right on the line for issuing but at a threshold where I would have been willing to wait a bit & see what happened as the storms moved deeper into the questionable environment in our CWA. Without the tools we're testing this week I likely would have issued a SPS given the lack of reports from this storm & waited a few scans to see how it reacted to the environment across our CWA. In this case the storm began to weaken almost immediately after I issued the warning.

GLM data also was not that impressive on the storm even showing the weakening trend while reaching peak ProbSevere & MESH values I've witnessed with other storms in the west this week. I think this even reverse trend in GLM lightning activity added to my decision to issue a warning based on seeing it with other severe storms in ABQ/MAF so maybe I was anticipating a trend that doesn't actually exist.

Warning decision making relies on confidence in your understanding of the near-storm environment, & that the tools you are using are accurately depicting what is going on in the storm/environment. With this week being the first time we have seen GLM & all-sky products, & with limited use of ProbHail/Wind/Tor, I found it hard to decide which ones to trust when faced with conflicting warn/don't warn information between them and alongside more familiar conventional  products. Obviously this will change as we get more familiarization & training with the products which is one of the primary benefits of these HWTs!

GLM/ProbSevere loop of event:

All-sky CAPE/MRMS RALA loop of event:

Peter Sunday