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