IND TVS

15 min prior to 1.75″ hail and 20 min prior to baseball-size hail, a supercell tracked NNW-SSE through Vermillion Co, IL …the Probsvr nailed the values for ProbHail at 96%, VILD 4.3, and a well defined TVS (100kt G-G) and strong MESO on NEXRAD ~ 7k’NUCAPS SVR TS values kinda nailed it in Ern IL :

East Central IL  (green dot) MU and FCST SFC CAPE were > 4000, LIs were > 12, DCAPE > 1000 (~50KT Gusts), SHIP > 1 and LR H8 – H5 ~8SRM showed Storm Top Div > 130kt 12 min prior to the Baseball Sized hailThis storm is not diminishing, with Storm Top DIV remaining well over 100ktEastern end of MCS continues to chug thru central IN (2130-2300z), ProbSVR ~ 23z looking good, more warnings on the way

GLM Flash Event Density vs Centroids

Viewing some marginal severe storms in northern Idaho from GOES 17 in this example. In the first image is the traditional Flash Extent Density product. However, have modified the color curve (User -> Awips -> GLM_FED_DC) to provide some enhancement to the lower values as detection efficiency seems to remain lower over ID/MT as we have found in MT/WY in previous days. While this is overall helpful in picking out some stronger storms, the large 8km grid boxes take up a lot of screen real estate when viewing over background satellite imagery.  Also the strongest storms are somewhat lost in the lightning data of the surrounding storms.

As an experiment, tried loading up the Flash Centroid Density Product. By turning on the interpolation and setting the max value to 10, this really helped to isolate and highlight the strongest cells. Of note is the cell moving toward the north, west of Missoula. Picking out the lightning jump in this storm was easier viewed on this Flash Centroid Density product, and comparing its strength to surrounding storms was also easier. It is also helpful that the product has overall small footprint.

— warmbias —

ProbSevere in MCS

Watching the MCS evolve over Indiana, ProbSevere became increasingly hard to use. The object continued to change in size and in number, so it was hard to trust the probabilistic values. Ideally, I would have liked to see one on the eastern flank where the strongest velocities were, another on the western flank where the reflectivity is higher, and perhaps one or two more in between.  However, since the orientation of the MCS continues to change, I’m not sure if that would continue to be the preferred object count and location.  Bottom line is to use ProbSevere with caution with lines, bows, MCS’s or anything with ill-identifiable cells.

-Tempest Sooner

Were there indications there could be large hail in eastern IL?

Short answer: Yep.

NUCAPS Modified Sounding near Champaign/Urbana, IL from 18Z pass.

Since there were no 18-19Z special soundings from the IL/IN area, I looked to the AllSkyLAP CAPE which was only getting GFS retrievals in the ILX area. Those values were around 2300 J/KG or so.  The NUCAPS modified sounding near Champaign/Urbana, IL (shown above; the closest green dot to the storm that produced the severe hail), suggested more than 3500 J/KG of MLCAPE. Yesterday’s NUCAPS soundings suggested that the NUCAPS CAPE values were a bit high, but the ProbSevere MLCAPE values at the time of the baseball size hail in Westville (2105Z) were near 2773 J/KG.  So, yes, plenty of sources suggested high CAPE and thus there could be large hail in the area.

Also of note: The operational GOES 16 CAPE did not show any values because of clouds across the area.

-Tempest Sooner

VisIR Sandwich of MCS

VisIR sandwich product has been a very useful way to combine the high res visible imagery with the cloud top temperatures. However late in the day as the sun angle gets lower, the image gets darker. One way to remedy this is to adjust the composite options (right click on legend), and equally lowering the Gamma setting. This will brighten up the image and allow better utility into the low sun angle hours before sunset.

Default:

After:

How to adjust settings:

 

— warmbias —

AzShear: The Good and the Bad

Low Level AzShear (0-2km) correctly identified an area of rotation associated with the western supercell, however, AzShear was also saturated above 0.01 along the leading edge of the bow echo in the MCS as well. While it’s good to drawn attention to the latter area, as it was producing severe wind (61kts), it was not tornadic.  Additionally, there is some noise in the merged LL AzShear that wouldn’t exist in the single radar AzShear. I believe single radar AzShear would perform better in this situation.

Clockwise from Top Left: KIND 0.5 Ref, 0.5 SRM, 0.5 Vel, Low Level Az Shear (0-2km)

-Tempest Sooner

Prob Severe Object Identification

Prob Severe failed to identify a strong storm developing in radar sparse coverage area near Bozeman, MT. The storm did show up on MRMS composite reflectivity, ENTLN, GLM Lighting and had rapidly cooling cloud tops, so not sure what was missing to have the storm identified by Prob Severe.

–warmbias–

FED Gives Precursor to Strenthening Supercell, but…

Watching the last storm in the line that is still in Illinois, the Flash Extent Density values started climbing rapidly (between 1947Z and 2020Z), which suggested to me that I should start paying attention to it. Upon interrogation, the velocity started to change from being more convergent to rotational, and eventually it appeared that a tornado was likely per the KIND radar. Interestingly, that was when the FED fell rapidly (2022Z).

Clockwise from Top Left: 0.5 KIND Reflectivity, 0.5 KIND SRM, 0.5 KIND Vel, FED

There was also an increase in FED after the tornado signature became less intense, but when it wrapped up again, the FED decreased again (not shown).

Interestingly, I also looked at these same data with the new color curve that Jonathan and Kristin worked on today, and the increase and decreases in FED were not as clear, and I don’t think it would have drawn my attention as quickly. Perhaps the lower values need to be more muted or less bright, but still within the same the rainbow color curve.

Clockwise from Top Left: 0.5 KIND Reflectivity, 0.5 KIND SRM, 0.5 KIND Vel, FED

-Tempest Sooner

5-min FED Colormaps

Testing a new colormap for FED using the Rainbow colormap in Python.  The first image depicts the modified 5-min FED with the modified colormap.  There is more variation on the lower end of the 5-min FED.  Will this colormap depict the variation in the more intense convection. The second image is the original 5-min FED colormap.  – Jonathan Wynn Smith (ESSIC/UMD)

Love the AllSky TPW!

Here’s just a quick example of today’s TPW over the Midwest where a complex MCS and discrete supercell are located. The blended TPW is very low-resolution and therefore you miss the enhanced values that might be located over IL compared to the rest of the upper Midwest and southeast U.S.  The AllSky products in IL are mostly using GFS, which may or may not be reliable, but at least it gives a better emphasis and resolution in where to focus your attention….as well as data underneath the severe storm complex. Over central IL, the TPW values are around 1.5 inch vs. the 0.9 inch for the blended TPW.

Animation below shows: Upper Left AllSky All Layer TPW, Upper Right AllSky sfc-900mb TPW, Lower Left Merged TPW, Lower Right Blended TPW

Below is a screen shot of the MRMS loaded at a similar time over the TPWs to see the impact of the cloud cover.