One last gasp...before exiting ICT CWA

After spending a good majority of ops in the CWA, the squall line attempted to reintensify before exiting. ProbWind remained high (>85%) through much of the non-severe life-cycle of the line as it moved east past Wichita. The northern portion of the line quickly intensified at 2330 UTC. ProbSVR began to increase prior to this and jumped to 76% at 2330 eventually hitting 94%. MESH increased to 1.5" during this time. A warning was issued for the newly intensified line segment at 2351 but easily could have been issued a bit earlier given surge in reflectivity. 4-panel has ProbTOR (UR), ProbHail (LL), ProbWind (LR).

NUCAPS comparison with 18Z soundings

NUCAPS made a pass over the lower plains near 19Z, shortly after the special soundings at OUN and TOP.  The strong cap on the OUN sounding is apparent in the smoothed out NUCAPS data.  Moisture profiles look representative as well.
It would be more

(Above:  OUN 18Z sounding)

(Above:  NUCAPS near OUN 19Z pass)

(Above:  NUCAPS modified, east of OUN 19Z)


At Topeka, the temperature and moisture profile also looks generally representative. 

(Above:  18Z TOP sounding)

(Above:  NUCAPS sounding near TOP)

(Above:  NUCAPS modified sounding near TOP)

-Forrest

A range of flash sizes and energies

A leading-line, trailing-stratiform mesoscale convective system near the triple point in Kansas shows the diversity of flash properties observable from GLM.

The flash properties correspond well to the basic structure of the MCS.
- Leading line: relatively small, frequent flashes
- Trailing stratiform: large, infrequent flashes every other minute or so

Flash extent density in the extensive stratiform discharges are 2 or 3 in some locations, because the GLM flash grouping algorithm tends to split these large flashes.

In total energy, the infrequent stratiform flashes are quite bright. The total light output of one flash equals that of the numerous flashes in the convective line. The large flashes tap an extensive reservoir of charge and discharge it all at once, releasing the electrical energy in the form of light as the channel is heated.

Some of the extensive flashes, such as the one below, show the path of the lightning channel as it crawled through the stratiform region. The brighter trails within the overall flash were long branches of the same flash that were lit up by current flowing along each branch.

The extensive flashes correspond well with expected microphysical trajectories in the stratiform region, propagating from the main convective line, and then bending sometimes north and sometimes south into the enhanced stratiform reflectivity patches of about 40 dBZ. The northerly flashes sometimes follow the curved path implied by the reflectivity pattern to the north of the main convective line.

-Eric Bruning

ProbSevere Jump

The two images show how ProbWind jumped from 24% to 76% and ProbHail jumped from 19% to 85%, in 8 minutes.  This trend, combined with 1-minute ABI data showing increasing storm strength, 1-minute GLM data showing increasing lightning, all in prime environment, made it easy to issue a high confidence SVR warning.

-Kevin

Trailing Stratiform Region Flash aka Science Works!

As expected, an extensive trailing stratiform region developed with the maturing MCS as it moved into the central part of ICT area. One long flash was captured at 2146 UTC. Of note, flash area was in excess of 3000 km2 in the stratiform region. The total energy in the stratiform region was equivalent to that in the updraft region as the large charge reservoir was extenguished. More frequent replenishment of charges in the more turbulent storm-scale updraft compensated for the individually smaller/weaker flashes there (ref McGorman, Bruning). There was a depression in flash area along the line while the group area had more continuous flash sizes along. The larger number of groups helped make this more continuous versus the lower flash count. - SCoulomb (with help from Eric & Chris)

GLM look at line of storms in ICT

Attempted to diagnose updraft intensity with line of storms in western part of ICT area at 2120 UTC. The middle storm had highest energy (60J) and flash rate (14). Flash size was relatively large (~270) compared to the other two storms on its flank (<100). Northern most storm had largest flash sizes (>800) in the anvil. Really nothing that MRMS wouldn't have indicated as far as storm triage.

SNPP NUCAPS DB Modified Sounding Success!

The 19Z Modified DB NUCAPS sounding was quite accurate with regards to instability parameters and the thermodynamic profile. 

A clear sky point (Figure 1) was captured and compared to nearby metars. NUCAPS Sfc temps/td's in the low 80s/upper 60s, respectively, matched nearby metar observations. In addition, the thermodynamic profile from NUCAPS (Figure 2) matched the observed sounding from Lamont, OK (Figure 3) and Topeka, KS (Figure 4) relatively well. 

As a side note, the DB Modified sounding did provide added value over the DB sounding with a more accurate thermodynamic profile as well as instability.

Figure 1. NUCAPS DB Modified sounding location

near Lamont, OK

Figure 2. Modified DB NUCAPS thermodynamic 

profile.  SFC CAPE of 3,916 J/Kg

Figure 3. Observed 17Z sounding at Lamont, TX

SFC CAPE of 3,059 J/Kg

 Figure 4. Observed 18Z sounding at Topeka, KS

SFC CAPE of 4,256 J/Kg 

- BO

KOUN Experimental Tornado Warning

The forecaster covering the southern Norman WFO noticed the tornado probability from ProbSevere Version 2 (All Hazards) rapidly increasing between 2114 and 2124 UTC Wednesday afternoon (Figue 1).  The rapid increase in tornado probabilities was due to rapidly strengthening low-level circulation.  ProbSevere here aided the forecaster to issue an experimental tornado warning--increasing lead-time and confidence in his decision making.  Storm chaser live video showed a tornado developed at 2139 UTC.

Figure 1. KFDR storm-relative velocity and ProbSevere Version 2 tornado probability valid 2114 - 2124 UTC 02 May 2018.

-J. Sieglaff

CI Algorithm in OUN

Monitoring the CI algorithm on 5/2 in the OUN county warning area, limited value was added. Values did increase in the scans leading up to convective imitation, however, in most cases these increasing probs were not associated with storms that actually did initiate (see animation below). Many of the higher values were well ahead of the boundary where we knew storms would not go. Back along the boundary where storms did develop, CI probs were either non existent (due to cirrus cover) or very low. There were limited instances of success. The only value I would say CI did provide was showing increasing probs in general across the area prior to CI. This could tell the forecaster that initiation is close, just not exactly where.

- Bucky

ProbSevere Aids in Experimental Tornado Warning

The forecasters in the Wichita, KS CWA noted ProbSevere tornado probability rapidly increased on a supercell thunderstorm that developed just ahead of a large severe squall line.  Figure 1 shows KICT 0.5 degree storm-relative velocity and ProbSevere probability of tornado contours rapidly increasing from 13% at 2048 UTC to 70% at 2056 UTC.  The velocity data shows a very strong, tight circulation.   The jump of the probability of tornado alerted the warning forecaster and after a very quick radar interrogation, he issued an experimental tornado warning at 2100 UTC.

Figure 1.  KITC 0.5 degree storm relative velocity and ProbSevere Version 2 tornado probability, highlighting the supercell ahead of the squall line valid 2048-2056 UTC 02 May 2018.

-J. Sieglaff