Lightning with first severe? storm

The first strong/severe storm developed around 1900z along the WY/SD border, at least according to ProbSevere.  Four-panel loop below shows GLM lightning products,  plus radar and ProbSvr in the lower right panel, from 1850 to 1910Z. In this case the GLM lightning alone doesn't really stand out for this storm, as far as I can tell. WFO UNR did issue a SVR at 1917z.

Also in the upper left panel the NLDN CG lightning is plotted along with GLM FED. The slight NW displacement of GLM is evident.  A.Cope

Afternoon Convective Outlook for AMA

Quiet conditions at the moment across the AMA forecast area.  A cluster of storms that was over the northeast portion of the region has recently pushed off to the east. Minimal cloud cover remains, although there is a small CU field left in the vicinity of outflow from the previous storms. Instability is steadily building across the region with AllSkyLAP CAPE values from 2000-2500 J/kg in many areas.  An ongoing 18Z balloon launch from AMA still shows a weak cap around 770 mb, but this should be overcome later this afternoon as diurnal instability increases. Guidance suggests instability will peak later today near 3500 J/kg. Lapse rates are also very steep, with 700-500mb lapse rates near 9 C/km. An upper-level impulse tracking through the area today will increase bulk shear values to around 40 kts. The surface dryline, which currently lies just west of the forecast area, should advance east into the area later this afternoon.

Expect severe storms to develop along/ahead of the advancing dryline within the next 1-2 hours. The moderately strong instability, steep lapse rates, and moderate shear support large hail with the initial development. The storms should eventually grow upscale into a line and more of a damaging wind threat.

19Z Surface Plot/1929Z Visible image

1828Z AllSkyLAP CAPE

18Z AMA RAOB - CAPE values comparable to AllSkyLAP

Alex Brown

AllSkyLAP over Northern High Plains

Working today as the Rapid City SD office. This area is under a slight risk, with convection expected to develop through a north/south corridor over the high plains.

Looking at AllSkyLAP stability indices to help evaluate the environment. The 4-pan image below shows  the north-south axis of instability over the High Plains, with CAPE (upper left) in the 1500-2000 J/kg range over SW SD. Upper right is lifted index and lower right is K index. The lower left panel shows whether the values are influenced by GOES data (blue/yellow) or if they are just GFS data (gray). Differences due to data type are noticeable in the CAPE image over western NE, but not so evident in the LI or K images. A.Cope

Forecast 5/17/18

A strong shortwave trough will continue to move across the Great Basin this afternoon, providing increasing southwesterly flow aloft downstream over the High Plains. The water vapor loop implies increasing forcing for ascent across the Southern Rockies with increasing mid/high clouds approaching the TX/OK Panhandles. Strong diabatic heating will allow scattered strong to severe thunderstorms to develop this afternoon and evening.

Fig 1. Increasing forcing for ascent noted over the Southern Rockies.

Rapid surface destabilization is taking place this afternoon with 18z KAMA RAOB indicating 700-500mb lapse rates of 9.1 C/km and surface temperatures near 90 degrees. The AllSkyLAP product suggests CAPE near 2500 J/kg with model progs increasing to near 3500 J/kg by peak heating. Deep-layer shear is a bit strong than previously anticipate with 0-6km BWD generally between 35-45 kts. This will be sufficient to sustain organized updrafts with some storms becoming supercellular initially before growing upscale into linear segments.

Fig 2. AllSkyLAP CAPE of 2000-2500 J/kg as of 1830 UTC.

Storms are expected to initiate along the dryline on the Caprock, moving in a general eastward direction. Lift may be enhanced across portions of the Panhandles by an outflow boundary originating from the ongoing convection over northwest OK. The Bunkers RM storm motion from the W and NW only 5-7 kts, suggesting a potential for heavy rainfall with any right movers. The very steep lapse rates and strong instability will support a large hail threat, with isolated sig hail reports possible this afternoon. There is also a potential for isolated damaging wind early in the storms' lifecycles, becoming more widespread as storms grow upscale.

wall_cloud

Week 3 Day 4 Operations

Today we will be operating in the Rapid City, SD and Amarillo, TX CWAs monitoring the area for storm development later in the afternoon.

-Michael

Day 3 Wrap Up

Wrap-Up and feedback from the day yesterday is listed below. Yesterday was a pretty slow day weather wise which gave the forecasters a good opportunity to explore more of the products.

GLM

A summation somewhere between 1 and 5 minutes would be perfect, not sure of the 2 minutes is the
perfect answer

Struggled to find a need to have the FED and the event density. FED and flash area seem to provide
the most use when using it within warning operations

Flashes and subsequently FED seems to be the most intuitive product

Hands on training would be the most imperative to get people up to speed on using GLM data in
operations and what and when the products are useful

Need to stick with simplicity, especially when presenting the information to the public or to EMs

It is important to use in conjunction with other lightning data to see CG strokes

GLM seems to provide a much larger coverage in stratiform areas or areas behind a line

ProbSevere

Environment yesterday was not conducive for ProbSevere to be real useful

Had some pulse storms and microbursts that weren’t detected

Still took a little while to catch on to the hail in the Texas storm as the background environment again
wasn’t real good

The object tracking was a little junky yesterday. It would combine cells and then split apart and then
combine again and so on.

Might be worthwhile to try to use reflectivity at -10C, even if it was a minute or so later

NUCAPS

Liked the lapse rate procedures to compare to models and see how well things were handled by the
models

Soundings would definitely be useful outside of the balloon times

Yesterday the modified had a substantially better boundary layer representation compared to the
unmodified version

Useful to have a background satellite image to understand which soundings are useful

The DB soundings seem to have a lot more yellow points than the operational version

CI

Continue to struggle with the fact that the severe CI is higher in a lot of cases that the non severe

The jumps in probabilities are inconsistent between the two products and don’t instill much confidence
in using the product

To use the product it needs to really draw my attention with a consistent higher value in a field of lower
values, especially in the summertime southeast thunderstorm environments

The data is very noisy and jumpy especially in the more discrete cloud areas

All-Sky LAP

Had some problems in the Arkansas area where there was quite a bit of cloud cover and the GFS data
seemed to be convectively contaminated and undercut the CAPE values

Did show a nose of more unstable air coming up into southern AR where storms did intensify slightly

Would be worth trying to have a CONUS “nest” using a little more high resolution model data to fill in the
cloudy regions

Like having the All-sky compared to the baseline product to fill in the cloudy areas, but some
improvements would be desired

Worked pretty well in Texas where there was very little cloud cover

GOES-16 Products

Loaded the Day Convection RGB, but need the higher resolution to be useful

Love using the Day Cloud Phase Distinction in initiation stages

Looking at the three WV channels on their own is still the most useful

Generally, the RGBs are difficult to understand and interpret without a lot of experience, even with
quick guides and training

The 1 minute updates are amazing

Lightning Shift

A severe thunderstorm developed over western Sterling County just within the SJT CWA. Hail was the main threat, with 1.5" hail expected. At the same time, and additional thunderstorm was developing over eastern Glasscock County immediately to the west of Sterling County.

A few minutes later, the most intense lightning began shifting to the west into Glasscock County. The storm began intensifying rapidly at that point.

Within a few more minutes, the Glasscock County storm became the dominant storm. hail up to 2" in diameter was expected. The Sterling County storm weakened a little as the Glasscock County storm took over.


Gary Cannalte

GLM Total Power

We had a brief discussion on the utility of Total Energy and what a "large" value may be. I noted this storm in southern Arkansas was indicating a 2 minute Flash Extent Density near 45  which is near the high end of the default color table. The Total Energy registered 240 fJ at this time, which is double the top end of that respective color table.

It makes me wonder what all factors contribute to high energy for a particular storm over another storm in a similar environment. What processes are at work in this instance?  It's all very fascinating and could have potential benefits in the warning environment should a correlation become evident.

Fig 1. Note the Total Energy in the bottom left panel is 2 times the color table maximum.

wall_cloud

NUCAPS Soundings and Imagery

The first image below shows the afternoon NUCAPS soundings over AR and vicinity, displayed over the GOES CH2 Vis and NUCAPS 850-500mb lapse rate imagery. The image has data only for the "green" soundings, i.e., those for which both the IR and MW retrievals were successful. This results in a lot of "holes" in the NUCAPS images. Taking away the NUCAPS image (second screen capture below), it's not exactly clear why some of the soundings are green and some adjacent ones are yellow, e.g., over southern AR, as the cloud fields below look very similar. Perhaps the QC process could be modified so that more sounding are included in the creation of the NUCAPS images, as these are much quicker to examine than looking at each individual sounding. BTW, the NUCAPS lapse rates over southern AR are only about 6.5 deg C per km, not particularly impressive. The t-storms in AR today have been mostly sub-severe.  A.Cope

Odd ProbSevere Cell ID

A cluster of several distinct storm cores were identified by ProbSevere moving across west Texas this afternoon. However, for a brief period of time, the cores were combined into one storm ID, event though the cores still looked distinct.

2254Z-2312Z ProbSevere/MRMS RALA Loop

Alex Brown