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