Water vapor imagery early this afternoon is showing a deep closed upper low over CA with broad southwesterly flow across the southern plains with a weak disturbance moving through the flow which seems to be enhancing/sustaining convection moving through the western portion of the forecast area. Visible imagery shows well the ongoing convection as well as a boundary situated across KS southwestward into the OK/TX panhandle.

A quick look at the GOES-R CAPE showed values generally in the 1000-1500 J/kg except along the Red River where lower values were shown below 1000 J/kg.  There definitely appears to be some influence of cirrus and mid level clouds associated with the ongoing convection affecting the output.

Comparing the GOES-R CAPE to the SPC mesoanalysis mixed layer CAPE it appears the values are too low, especially in the Red River area where values close to 2000 J/kg were noted.

The continued moist southeasterly flow into the region today south of the ongoing convection should interact with outflow boundary from ongoing convection and initiate new convection across the southern portion of the forecast area.

Jack Bauer

While we were writing up a previous blog post, we noticed rapid increase in the ProbSevere for a storm to the west of the OUN radar. The ProbSevere quickly ramped up from 9% to 94% as seen in the two images below.

Seeing that rapid increase was noticeable to both of us as were were typing up other blog posts and prompted us the interrogate the radar data. While the core looked small initially, the idea shown by the ProbSevere was right on.

Finally, with the location of the cell being right under the clouds from upstream convection (see image below), it led to N/A values on the satellite data.

-SRF

We are tasked with assessing the pGLM and GOES-R/UAH CI products. A very moist and unstable atmosphere is present over much of the LUB CWA with an ongoing MCS exiting the northeastern portions of the CWA. GOES-R/CIMSS layer CAPE values range 400-500 J/KG for the northwestern portions to 1200-1400 J/kg for southeastern portions. PWATs also possessed a sharp moisture gradient from NW to SE, with values near 0.60″ NW to 1.40″ SE, along with dewpoints in the mid 60s building across southern half of the CWA ahead of the eastward moving MCS.

RAP13 forecast sounding centered just south of Lubbock around 18Z indicated MLCAPE around 1600 J/KG, fairly close to the GOES layer CAPE values. Freezing level and -20 C heights are around 20k ft with modest moisture in hail region, though very moist low levels will help overcome some drying aloft. Expect large hail and damaging wind gusts to be an issue with any discrete cells, as well as isolated tornadoes possible due to modest low level shear/helicity. Will monitor CI for possible development south of LUB/ongoing MCS in hopes of catching pGLM/lightning jump with storms as they develop.

Brick Tamland

As we were spinning up with the OUN CWA, we received word that the KFDR radar has went down and technicians are on their way to fix it. Looking at the latest radar (1821Z), the strongest storms were near that area and it will complicate the warning process.

With the surrounding radars seeing the current storms around 15kft, this will be a good opportunity to try out the ENI Lightning Data, both the Thunderstorm Alerts and the Cell Tracking with Time Series. Here is the latest Significant/Dangerous Lightning Alerts for that area at 1832Z.

There are a numerous boxes with the default settings and one of the other groups was going to set a higher threshold, which we will try out shortly.

Finally, taking a look at the cell tracking data, we area able to pick out a couple stronger cells, with one location outputting over 100 flashes on the strongest cell.

-SRF

We decided to issue a warning at 2323 UTC for Lubbock county on a storm that was moving eastward towards the city of Lubbock. The ProbSvr increased to around 59% at 2316 UTC with a MESH of 0.76 inches.The PGLM data and Lightning jump data at 2316 UTC were not very impressive with flash density less than 10 flashes (upper left in the image below) and the Lightning jump showing values less than 1 sigma (lower left in the image below).

Based on the base radar data from the all tilts display off of the MAF radar (LBB was too close to the storm and not able to see the top of the storm), we began writing up a severe thunderstorm warning at 2320 UTC which was issued at 2323 UTC.  It was noted that at 2322 UTC the Lightning jump algorithm displayed a 2 sigma value on the storm (we did not see this is real time as we were writing up the warning), while the PGLM showed an increase in flash density to around 23 flashes which was still relatively unimpressive.

In this instance the PGLM and Lightning jump did not really provide any significant factor in the warning decision although the 2 sigma Lightning jump is a positive sign but in this instance did not outperform traditional base data storm interrogation.  A large hail report of 1.75 inches was received just southwest of Lubbock at 2333 UTC.

Jack Bauer

An isolated convective cell just ahead of a line of thunderstorms became overrun by the line of storm and was absorbed by the line which resulted in an increase in the updraft and storm intensity.

The ProbSvr was showing increasing probabilities around 30% by 2216 UTC outlining an area that encompassed the storm merger as well as another cell to the north.

By 2220 UTC the ProbSvr had increased to 73% and now encompassed the merger as well as the storm to the north.  The base radar data was not very impressive and I had no thought for a severe thunderstorm warning despite the increased values of the ProbSvr.  This is another case where the ProbSvr has limitations and shows higher values when you have storm mergers and in these situations it should be used with caution.

The PGLM data began to increase at 2215 UTC and continued to to a max density around 31 flashes at 2218 UTC before slowly diminishing back to below 10 flashes by 2224 UTC.

I felt the PGLM data did provide me with improved situational awareness and help focus my attention to this area as these storms had been quite weak in the several scans leading up to this event.  I also can see where the one minute resolution of the PGLM data could provide an advantage to show a rapid increase in storm intensity between radar scans.

Jack Bauer

The Convective initiation product showed an area of 51% probability in the south central part of Parmer county in the far northwestern part of the LBB CWA at 2015 UTC after showing some 10% probabilities at 2000 UTC.  By 2030 UTC the convective initiation probability increased to over 60% and also identified another area with a 74% probability.

Looking back at the radar data in the loop below the first 10+ dbz reflectivity values appeared at 2037 UTC.

The first 35 dbz value occurred at 2048 UTC in the west central part of Parmer county.

I think the CI product successfully identified this initiation with over 30 minutes of lead time again highlighting it’s situational awareness value.

Jack Bauer

I didn’t get a chance to look at the NUCAPS soundings on Day 1 but as soon as the pass occurred today we looked at a sounding that was about 60 miles east of the storm of interest that we have been following in the northern portion of the MAF CWA.  The NUCAPS availability point was located in a brief area of clearing within the cumulus field but we were a little uncertain whether or not clouds interfered or not.

However, the data did look reasonable as the temp was close to surrounding obs, though the dewpoint appeared to be low compared to surrounding observations.  The SBCAPE in the NUCAPS sounding was about 245 J/kg which was significantly lower than the GOES-R LAP CAPE observation which was around 1000 J/kg.

We modified the sounding to increase the dewpoint to 59 degrees to be better in line and this resulted in SBCAPE of just under 1000 J/kg and lined up well with the GOES-R CAPE.

Jack Bauer