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

Posted in NUCAPS on by Michael Bowlan.

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

Posted in Mesoscale Discussions on by Kristin Calhoun.

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

Posted in GLM, HWT on by Justin.

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

More Observations of AzShear

Posted in AzShear on by Thea.

It seems to me the merged product, particularly the 0-2km, highlights nearly every updraft whereas the AzShear seems to do a good job discriminating, and highlights the cell most likely to have strong rotation. In this case the couplet shows up in the western side of the AzShear display and is associated with an embedded rotating updraft, while the AzShear does not highlight the cells further southeast which show weaker rotation. However, the merged product (bottom right) shows bullseyes on all these cells which would make it difficult to triage which storms need attention.

-64BoggsLites

Another Busy Day Ahead

Posted in News on by Michael Bowlan.

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

Posted in AllSky, HWT on by Michael Bowlan.

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

Initial impressions of AzShear

Posted in News on by Thea.

Two things jumped out at me right off the bat regarding AzShear. First, the couplet in AzShear really jumps out and your attention becomes focused on this area for further interrogation. It’s a great tool to further investigate the rotation couplet and storm structure in the base data (top picture).  Second, The couplet really jumps out in the AzShear product much better when compared to the merged products (bottom figure). Very impressive!

  -64BoggsLites

Here comes the moisture

Posted in AllSky, HWT on by Justin.

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

Comparing TDS Height and CPTI

Posted in AzShear, CPTI on by Michael Bowlan.

An embedded supercell produced a significant tornado just west of the KLSX radar near St. Louis around 6pm CDT. The tornado produced a tornado debris signature and impressive debris ball (>65 dBZ) at its peak intensity.

The tornado debris signature reached a height of ~10kft at the 10 degree elevation scan, characteristic of an EF-2 tornado.

This case provides a great opportunity to investigate the performance of CPTI. The algorithm identified a maximum probability of strong tornadoes of 22% and a maximum low-level AzShear value of 0.030 /s. Based on the AzShear value, it seems the CPTI for strong tornadoes should have been stronger.

A little digging showed that the MRMS STP value was 0 near St. Louis, while the SPC Mesoanalysis page showed an STP of 4. This discrepancy explains the suppressed strong tornado CPTI and should be investigated. Perhaps there is a latency issue with the MRMS STP data.

I really like the CPTI product for clear-cut tornadoes and see it being very helpful for IBW updates for an ongoing tornado.

-Atlanta Braves

ProbTor Spikes to 72%, But is it Legit?

Posted in AzShear, GLM, GOESR, ProbSevere, Total Lightning on by Michael Bowlan.

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 bullseyes 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 bullseyes which were located slightly to the NW of the primary rotation track, never showed up in the new azimuthal shear product. -Roy