Storm split represented in GLM

As the supercell moved out of OK it shed a left split before turning more east. The GLM captured this split with higher event density values associated with each updraft core. The GLM flash event cores became increasingly separated as the left mover moved north. - S Coulomb

Active Severe Weather Day in Hastings, NE

ProbSevere was very helpful for hail and wind, but especially hail, which is the main threat as of late afternoon. ProbTor was lagging behind base data by a volume scan, which was critical as a tor warning was issued several minutes before probtor spiked up from 7% to 46%

GLM 1-min Total Energy overlaid with 1-min vis cued me in on areas of deep convective development. Additionally, ENI lightning data overlaid with GLM gave me a good indication of where anvil flashes were propagating away from the main updraft.

GLM readily caught my attention as energy was displayed as an image, with more intense lightning activity showing up 'hotter' in the magma color table.

Supercell that moved eastward just north of the KS/NE border exhibited high total energy while located in our CWA. It appeared that as the storm's total energy began to weaken as it moved away from our CWA, a confirmed tornado was reported in Gage County NE at 7:23PM local time (see bottom two images). Lightning jump?

First look at multiple GLM products!

Clockwise from upper-left:  GLM Total Energy, Flash Extent Density, and Flash Area.  ENI is overlaid with Total Energy and Flash Area.

Saw an interesting spike with the cell near the center of each image, a couple counties south of Hastings CWA outlined in pink.  The spike with this cell happened near the end of the loop after 2200Z.

My warning partner Tom announced that the GLM experimental one minute data was available while I was looking at some 5-min visible.  Excitedly, I overlaid the one minute lightning on top of the satellite (time matched) not realizing I might see something tantalizing, so only got 5 minute updates of the one-minute lightning data.

A strengthening storm just south of Hastings CWA showed a sudden spike in Total Energy (TE) at 2217Z.    A sequence from 2212-22Z saw TE bounce from 34 - 111.7 - 40.5fJ.  Flash density remained 5-10 throughout.

Coincidentally, there was a spotter report of hail 2.5" at 2212Z with the cell.

I enjoyed the discussion I had with the developers today, and appreciate and like the new color scales they quickly developed for us since I had made this above gif.  Tomorrow, I will revisit GLM, hopefully with better planning!

-Forrest

GLM Fields for Severe Thunderstorm

Mature storms northeast of our forecast area later in the day provided a great demonstration of a few of the lightning fields and how information from them is relevant. The Flash Extent Density and Total Energy (top left and bottom left) highlight the regions of greatest lightning activity corresponding to strongest and most persistent updraft regions. Further, Average Flash Area (upper right) further delineates updraft regions by highlighting the smaller flash areas. Brief lightning activity is sometimes apparent out in the anvil regions, and have appropriately larger flash areas.

-Bucky

Convective Initiation in VC of Hastings (Derived Products and LPW, and mention CI)

Convection rapidly initiated along a frontal and sharp moisture boundary in the Hastings CWA near 2000Z.

In the animation below, LPW 0.9-0.7 rapidly increases, from near 0.39 in the area near 1630Z, to as high as 0.6 by 2000Z, then quickly to 0.65-0.71 only 30 minutes later.  Initiation was very near 2000Z.

Before 2030Z, the area of maximum LPW had relatively thin cirrus moving over.  After 2030Z, thick anvil quickly moved over the area of maximum depicted moisture.

ENI lightning is overlaid.  Lightning first appears at 1958Z.

On a side note, I initially launched LPW stand-alone.  The loop had some blank frames.  On closer inspection, updates happened usually every approx 30 mins, but occasionally, a frame would update only one minute after the last, causing the blank frame.

The increasing moisture aloft was paralleled by increasing convective parameters as seen in the derived products.

K-Index, a parameter sensitive to mid-level moisture rose from the low-mid 20s before 16Z, to a more convective friendly 30+ by near 1830Z, to remarkably high values near to above 40 by 2000-2030Z.  Changes to derived CAPE and LI were much more modest.  In the 4-panel below, clockwise from top-left is:  derived CAPE, Layer Cloud Type, LI, K-Index(bottom left).

The K-index was also diagnosed as increasing quickly on RAP, but overall values in the model were lower.  As seen on the SPC RAP MesoAnalysis, the initial development happened along the moisture gradient at 925mb.

This lends hope that these products will be useful over areas that RAP analysis does not cover, such as oceanic areas.

As a last note, CI didn't show a strong signal beforehand in the area of initiation.  There were some transient values above what seemed to be widespread unfocused nominal values 0-20%, but it didn't clearly key in on the cells that went on to develop rapidly.  As mentioned earlier, there was some cirrus in the area leading up to development, but it did not seem very opaque.

-Forrest

Spin up of another tornado from a long-lived supercell

A long-lived supercell thunderstorm transversed across the northern Wichita, KS WFO and into the Topeka, KS WFO Tuesday evening.  This supercell had exhibited ProbSevere All Hazards probability of tornado values that cycled with the intensity of the low and mid level circulation.  Between 2342 UTC and 2358 UTC the probability of tornado increased from near 50% to over 90% as both low and mid-level rotation quickly strengthened (Figure 1).  This storm produced at tornado at 0004 UTC 02 May 2018.  Forecasters have noticed with many of the long-lived supercells, the cycling of probability of tornado values related to cycling of mesocyclone strength.  This is giving forecasters good confidence in how to use the probability of tornado information in their decision making.

Figure 1.  KICT 0.5 degree storm relative velocity and ProbSevere All Hazards probability of tornado 2342 - 2358 UTC 01 May 2018.

-J. Sieglaff

NUCAPS/RAOB Comparison Over Dodge City, KS

The Dodge City, KS WFO launched a special 1900 UTC sounding, roughly the same time as a NUCAPS pass. Therefore, comparisons were made between the RAOB and a nearby NUCAPS. The NUCAPS profiles were not automatically modified, so user modification was needed. The surface temperature and dew point were both adjusted up roughly 5 degrees to match that of the radiosonde profile. The rest of the NUCAPS profile matched very well with the raob in terms of general shape. The 500 mb temperature in both profiles was -12C, while the 300 mb temperature was -43C in both. The NUCAPS profile captured drying between 700 mb and 500 mb, and moistening above. Upon modification of the NUCAPS surface conditions, the thermodynamic fields matched very well. ML CAPE was around 2000 j/kg in both, while SBCAPE was around 3060 in NUCAPS and 3200 in the raob. The LCL in the NUCAPS profile was around 5100 ft, while that in the raob was closer to 5500 ft.

On a similar note, a quick way to gauge the accuracy of the NUCAPS LCL in the absence of a radiosonde is to compare with cloud bases (if present) in surface observations. In this case, the DDC surface ob reported FEW at 5500 ft, matching that of the radiosonde.

Finally,

- Bucky

Buttermilk gets churned

An eastward moving supercell narrowly misses the town of Buttermilk, KS. ProbSVR was consistently above 90%. The previously tornado-warned storm lost a low-level circulation and ProbTOR dropped to <10%.

The 1-min visible satellite imagery of the storm around sunset revealed persistent overshooting tops and an above anvil cirrus plume with this storm. The above anvil cirrus plume is an indicator of a particularly strong updraft and potentially severe storm. A flanking line is revealed on the southwest portion of the storm as it advances through Buttermilk

 - SCoulomb and Bucky

GLM flash area product

GLM flash area product shows a nice correlation between the overshoot in VIS and a small (~110 km2) flash size. Flash size increased in the anvil downshear from the updraft and reached values ~420 km2. The highest total energy values were downshear from the overshoot. FED values (no shown)

were 1-2 in the same region.

Possible Tornadic Circulation in southern Dodge City, KS WFO

Early Tuesday evening, 0-1 km storm relative helicity had increased over the Central and Southern Plains.  The DDC crew noticed a rapid jump in ProbSevere All Hazards probability of tornado between 2328 and 2336 UTC--going from 10% to 70% in the 8 minute time period (Figure 1) in Comanche county, Kansas.  The forecast crew said the rapid increase alerted them to a rapidly intensifying low-level circulation and prompted an experimental tornado warning at 2339 UTC.

Figure 1.  KDDC 0.5 degree storm relative velocity and ProbSevere All Hazards probability of tornado contours 2328 - 2336 UTC 01 May 2018.

-J. Sieglaff