Day Three and a first NUCAPS pass over the East CONUS...

Just taking a quick look at the first NUCAPS swath over the CONUS.  I did want to point out the dropout in the swath, that unfortunately occurred along part of the SPC risk axis that stretched SW-NE from Illinois into the lower Great Lakes.  Although, the swath did obtain some soundings in the Marginal Risk area that encompasses much of Ohio.   Clicking  on the soundings in and around the Marginal Risk area indicated a regional location of higher instability.  Although soundings in the SW part of this risk area showed markedly higher instability values.


Image 1. NUCAPS Soundings, GOES-16 Vis, SPC Day One Outlook, ~18 UTC 22 May 2019



Image 2. NUCAPS Sounding from the Marginal Risk Area in Central Ohio, 18 UTC 22 May 2019


Image 3. NUCAPS Sounding from the Marginal Risk Area in SW Ohio, ~18 UTC 22 May 2019

Notice the are significant differences across this area with overall larger lapse rates and instability in the SW corner of the Marginal Risk Area.  So, it will be interesting to see what unfolds in this area.  As the NUCAPS data indicate, are some areas within the singular Marginal Risk Area more favored for stronger activity, and thus further partitioning is needed?

So, I just wanted to point out some quick features and soundings with the initial NUCAPS swath, although we're focused to the west today, over the southern Plains again.  We'll be watching intently for the next NUCAPS swath.

Comparison of All Sky CAPE to SPC Mesoanalysis CAPE products across Oklahoma

With convective initiation just starting, I wanted to to a comparison of the All Sky CAPE with the SPC mesoanlysis of SBCAPE and MLCAPE. Let's start with the SBCAPE (all images at 19Z on 5/22).



A very sharp gradient in SBCAPE can be seen in the mesoanalysis above, with values ranging from essentially nil in the northwestern part of the state to values over 4000 J/Kg in the southern third of the state.



The MLCAPE, as one would expect during maximum surface heating, is somewhat less, with values greater than 2500 J/kg running roughly from Tulsa to Norman, and values in excess of 3500 J/kg along the Red River.




Finally, let's look at the All Sky CAPE. These values are running about 500 J/Kg lower than the SPC MLCAPE in the Tulsa to Norman corridor, and as much as 1000 J/Kg lower near the Red River. However, it does nicely indicate the "shape" of the area that has MLCAPE, and emphasizes the area with the maximum values. This indicates the product is very helpful in a qualitative sense,  but specific values need to be used with caution.

Thorcaster

GLM struggling with intensifying supercell

The first CI of the day occurred just after 19Z. The radar appearance of the storm remains healthy and the ground-based lightning networks are as strong as they've been, but the GLM strength has (erroneously) dropped off dramatically.



-Atlanta Braves

Another Busy Day Ahead

Today looks to be another active day in the HWT,  with a moderate risk issued across portions of Oklahoma, Kansas, and Missouri. We will begin operating in the Norman, OK and Tulsa, OK CWAs monitoring for convective initiation with a risk for severe storms with all hazards possible including the risk for some strong tornadoes into the evening hours if storms can form and maintain themselves.

-Michael

All-Sky LAP PW Showing Rapid Low-Level Moistening

A comparison of the All-Sky LAP derived PWATs with 12z RAOBs shows that the LAP product is depicting PWAT quite well.



The PW retrievals were done mostly in clear skies (blue colors):



A four-panel plot of total PW and PW at different layers from 12-18Z shows rapid low-level moistening over OK and AR (upper right and bottom left panels).



The moisture return, in combination with diurnal heating, is resulting in a rapid increase in CAPE as suggested by the all-sky LAP product:



Ron Dayne

Here comes the moisture

The AllSky Layer Precipitable Water clearly shows the moisture return this morning into southern Texas and Central Oklahoma. PWATs across the Red River were ~0.5 inches early this morning and have now increased to ~1.5 inches this afternoon.



This product is a great situational awareness tool to survey the pre-storm environment. -Atlanta Braves

ProbTor Spikes to 72%, But is it Legit?

A semi-discrete cell tracked NNE of Little Rock, Arkansas. This storm developed a very tight reflectivity gradient on its southeast flank.  A few other notable features were an inflow notch and hook-like appendage.  Mitigating the severe potential with this storm was an outflow boundary displaced to the east of the updraft and low cloud flash counts (ground based) or cloud extent flash density (GLM).



The 0-2 km azimuthal shear generated what seemed to be a spurious bulleye's south of Searcy, Arkansas with values over 0.020 S-1. This data was input into the ProbTor algorithm, causing the spike to 72%.  The 0-2 km azimuthal shear derived with the new dealiasing technique never plotted values over 0.008 S-1. In fact, the bulleye's which were located slightly to the NW of the primary rotation track, never showed up in the new azimuthal shear product. -Roy

Prob Tor Prob

At times, there is some unnatural jumpiness in the Prob Tor Product. See the time series of 0.5 base velocity and Prob Severe/Tor below.



The first image is 2310Z. The storm is not overly impressive, with 5 minute FED max of 3 (not shown). Accordingly, the Prob Hail/Wind/Tor is 4/2/11 % respectively. The base velocity shows some decent winds of 45+ knots at about 3500 ft. above ground.



When moving to 2312Z however, the Prob Hail/Wind/Tor  are 4/12/61 % respectively. That is a huge jump in Tor Prob, but the velocity does not indicate any substantive change in organization, and the 5 minute FED has not changed.



Going ahead to 2316Z, the base velocity looks even less impressive, but the Prob Hail/Wind/Tor  are virtually unchanged at 3/12/61 % respectively.



Finally, at 2318Z, the Prob Hail/Wind/Tor  drop to 3/2/10 % respectively. These kinds of ups and downs despite any other evidence pointing to a change in organization made the products difficult to use in this case.

Thorcaster

Lightning jump with strengthening embedded supercell southwest of STL

A bump in GLM Flash Extent Density (bottom image, top left) was noted at 2020Z, and is coincident with the development of an embedded supercell within the convective line approaching St Louis (top image). This storm had a 60 dBz core extending above 20 kft (middle image) and a notable BWER associated with its updraft.

Total Optical Energy vs. Flash Extent Density...the steel cage match.

On the afternoon of May 21, portions of the Wichita (ICT) and Topeka (TOP) CWAs were under a Severe Thunderstorm Watch. To give one of the new GLM products a run through, I wanted to compare two cells of differing strength to see if GLM trends were helpful in nowcasting the cells. See the loop below.



The first cell of note was in Dickinson County (TOP CWA), and the second  was in Rice County (ICT CWA).  At the initial time of 2131Z, the storm in Dickinson County was already severe, and the Prob Severe Product supported this assertion with 68% prob wind and 76% prob tor. Meanwhile, the cell in Rice County was much weaker, with 50DbZ topping out below the -20C level (not shown), and prob hail/tor values of 2/1 % respectively.

At that time, the 5 minute flash extent density showed a little enhancement (max of 32), but the total optical energy was actually less (63 fJ) than several other, weaker storms in the area. Meanwhile, the storm in Rice county showed very modest flash density values (max of 9), but more significant TOE (144 fJ).

As the loop continues through the next 40 minutes, the intensity of the Rice County storm steadily increases as it moves northeastward, reaching Prob Hail values of 34% by the end of the loop (prob tor was still very low).  meanwhile, the storm originally in Dickinson County remained fairly steady state, with Prob Wind/Tor both at 68%.  It's obviously conjecture at this point, but maybe the TOE product on the Rice County storm was signaling some type of intensification. hard to tell from just this one case, but interesting to note nonetheless.

Thorcaster