ProbSevere Running Hot in SGX CWA

Looking at convection developing upstream across southern MO, I noticed prob severe had an object advertising 71% for TOR in the northern portion of the SGF  CWA (about a county and a half south of the CWA bondary. This particular cell does not show any rotation in the SGX base data, the Azimuthal shear doesn’t show much, and GLM lightning shows no electrical activity with this cell. I’m assuming the algorithm is keying more on environmental factors than anything else in coming up with this probability?


EWP Operations Tuesday, May 21

Today we are continuing on with the strong upper level trough moving into the Midwest. Today will be focused on mainly linear convection focusing on a QLCS moving through Arkansas and Missouri this afternoon. We will be operating in the St. Louis and Little Rock CWAs with an opportunity to also monitor for developing convection back near the center of the upper low in central Kansas later this afternoon.



An artifact in AllSky Products…

I was taking a first look at AllSky products this afternoon and put together a four-panel procedure. I expected to see some noise/sharp gradients in the data because differing pixel population methodology, but viewing a loop revealed an interesting artifact:

There appears to be an artifact in northern Arkansas that looks a little bit like a dinosaur head. This artifact is visible in parcel Lifted Index (to 500 mb), all PWAT products, and CAPE, but not in Total Totals, K Index, or Showalter Index fields. The artifact does not appear to be dependent on the Cloud Type field. Perhaps this artifact is associated with terrain in Arkansas but warrants further investigation. -Atlanta Braves

Comparing All Sky LAP CAPE with RAOBs

One of the forecast problems of the day for the LSX forecast area is determining how far north the reservoir of instability will extend. It may be useful to monitor the all-sky LAP CAPE product in concert with surface obs to assess the destabilization throughout the day. Looking at a comparison of the product with selected 12Z RAOBs, the product appears to have a reasonable representation of CAPE values so far.

The ILX RAOB is in the stable air well north of the warm front:

Although the MLCAPE at SGF is zero, the LAP CAPE produce is indicating around 400 J/kg of CAPE, which appears to reflect the MUCAPE in the sounding:

The LAP CAPE product underestimated the CAPE at LZK, but still gets the general idea:

While some of the details may not be correct, and it is blocky in places, the LAP CAPE product appears to be doing a reasonable job at depicting the reservoir of instability over the southern Plains. By 18Z, it showed the northward spread of instability in concert with the northward advancing warm front:

Ron Dayne


Looping the AllSky LAP CAPE product, moisture and instability is noted spreading northward toward the LSX CWA, which remains to the north of a warm front. One thing I noted is the western edge of the instability plume across eastern Texas jumps back and forth when looped. Not sure if this associated with the product itself or some other issue, but it was noteworthy. Otherwise the product seems to do a nice job depicting the instability plume spreading northward.




GLM RGB first view…

So, here’s an interesting concept…GLM data merged with GOES-16 IR (10.3 um) to create an RGB.  I think I like it!  Data fusion concepts like this are increasingly important in data-heavy AWIPS, especially during severe weather events and for situational awareness activities.  So, this RGB uses Flash Extent Density as the Red component, Minimum Flash Area as the Green component, and 10.3 um imagery from GOES as the Blue component.  The RGB has been tailored such that high FED results in increased red values, while Minimum Flash Area is reversed with respect to green colors (lower values equal increased green) and the IR temperatures from the 10.3 um band are also reversed so that lower temperatures result in higher blue colors.  So, for example, the end result is that high FED, low minimum flash area and cold IR temperatures result in brighter colors (near white) that physically indicate intense lightning, collocated with intense updrafts and cold cloud tops.  Meanwhile, anvil-type lightning (cold cloud tops, generally low FED and high minimum flash area result in colors more towards purple.  Colors leaning towards reds, yellows are relatively young, but intense convection in new, warmer convective cloud tops.  This shows up well, watching young convection feeding into an area of ongoing convection at the tail end of the convective complex today.  Ok…I’m writing this at the tail end of activities today, so I had to rush through this.  =)


Poor Correlation: GLM vs. Ground-Based Lightning Networks

Lightning data in the Texas panhandle late this afternoon showed low correlation between GLM output and data from ground based lightning networks. The output from the GLM flash extent density product appears underdone when compared to data from ENTLN, which has numerous areas of clustering in the vicinity of stronger thunderstorm updrafts. Meanwhile, the GLM flash extent density data shows low values and not much variance within the same general vicinity.  The problem does not appear as significant in western Oklahoma where the GLM flash extent density product shows much higher values in concert with clustering in the ENTLN data. It is difficult to pinpoint what might be causing this issue just by looking at the data alone.  Dave Grohl

Let’s do the wave

Seeing some interesting waves at different layers on the Simple Water Vapor RGB this evening. As a reminder, the simple water vapor RGB is made up of the low level water vapor image (band  10), the upper level water vapor image (band 8) and the clean window IR image (band 13).

There is one area of east/west waves along the Oklahoma/Arkansas border. The main contribution to those waves is the green channel, so we are “seeing” those waves based on the upper level water vapor.

The other is to the west of the severe convection in west Texas.  These waves have contributions from all the channels.


AzShear – Great Additional Tool for Tornado Warning Issuance

The best storm of the day so far produced a tornado with a tornado debris signature. The AzShear signature was textbook with a concentrated persistent bullseye over the couplet (center of image below):

This AzShear product is a great tool to increase confidence in the presence of low-level rotation. It should be used with caution, however, owing to the risk of misleading signatures. The signal north of the Greer storm is a result of convergence and/or bad velocity data: The reflectivity structure is more of a bow echo and the AzShear should be used with caution in identifying velocity couplets potentially associated with tornadoes. -Atlanta Braves

CPTI Increasing in Concert with an Observed Tornado

A tornado was observed via news footage near Mangum, OK.  The formation of this tornado was associated with an increase in CPTI for strong tornadoes to 46%:

The CPTI for violent tornadoes also increased to near 6% (not shown).

The ProbTor on this storm increased markedly between 2140-2155 UTC:

This increase was driven by an increase in AzShear:

Ron Dayne