ProbSvr gives good lead time

Looking at the use of prob severe in providing lead time. At 23:36z a report of ping pong ball size hail.

Analysis of prob severe and lightning jump 20 minutes before at 23:16z , shows the probSvr displaying 91% chance of severe, 46kts shear, MU cape 947, Mesh 1.07″, Growth rate strong: glaciation: strong, flash rate 28/min and 1 signa jump.

20 minutes later at 23:36z:  90% chance of severe, 49 kts shear, Mu cape 1157, Mesh 1.93″, Growth rate:strong, Glaciation: strong, 0 signa. ( however, jump did stay at 1 during 20 min duration.)

One report of ping pong ball size hail at that point.

Prob severe may be a good factor in issuing an early warning for a severe storm.

-thunder

ProbSVR20minout

ProgSvrPingPongHail

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Another Prob Severe Success East of Amarillo

This storm east of Amarillo produced quarter size hail at 6:25 PM, approximately 11 minutes before severe prob increased above 80%. There was a steady increase in values over the 30 minute before the severe hail report, from 20% at 6:02 PM, to 25% at 6:08 PM, to 62% at 6:12 PM. Correlated with the time of the severe hail report, severe prob values were 90%. Glaciation rates went from weak to strong ~20 minutes before the severe hail reports. Flash rates steadily increased leading up to the severe hail report but peaked ~30 minutes after the report.

-dryadiabat

Amarillo

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Eastern Amarillo CWA Storm

While we are watching storms in the Lubbock CWA, I kept an eye on a storm over the eastern portion of Amarillo CWA, near I-40.  The ProbSevere was 25% at 2308 UTC and jumped to 84% by 2314 UTC as MRMS MESH and total lightning flash rates jumped significantly (also the effective bulk shear was rather high in the mid/upper 40 knots).  The ProbSevere values continued to increase into the 90% range.  A 1.00″ hail report was received at Interstate 40 at 2325 UTC and after the report was received, a severe thunderstorm warning issued.  The good lead-time for this storm can be attributed to all predictors of ProbSevere–strong satellite growth rates, strong satellite growth rates, increasing lightning in a highly sheared environment and MRMS MESH over 1.00″.

NOAA/CIMSS ProbSevere contours and MRMS composite reflectivity valid 2308 - 2332 UTC 20 April 2016.
NOAA/CIMSS ProbSevere contours and MRMS composite reflectivity valid 2308 – 2332 UTC 20 April 2016. (click for animation)

-Sieglaff

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Storm Southeast of LBB’s RDA

Storm development has occurred southeast of the Lubbock, TX RDA in the Texas Panhandle.  While initially the all-tilts reflectivity looked promising, PROBSvr continued to indicate marginal severe potential.  Combine this with no significant lightning jump and low flash density on the PGLM array, the decision was made to hold off on a warning for now.LBBRadar

 

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Development of Sig Prob Severe in the Future?

Once again prob severe provides ~10-15 minutes of lead time using ~75% over typical radar thresholds. After we issued the warning we noticed signatures suggestive of significant hail sized (e.g., persistent deep TBSS, sidelobe contamination, transient BWER). This raises the question, could criteria be adjusted in the algorithm to provide sig severe guidance? This could be very useful operationally for the most high impact events that cause the most property damage and threat to life.

TBSS

-dryadiabat

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First Warning in San Angelo CWA

A thunderstorm developed along a residual outflow boundary/stationary front southwest of San Angelo Wednesday afternoon.  The forecaster group issued an experimental severe thunderstorm warning based on lightning jump data, ProbSevere output, and all radar tilts examination.  Figure 1 below shows a loop of 0.5 degree KSJT reflectivity and ProbSevere contours.  ProbSevere first exceeded 50% at 1952 UTC, 60% at 2002 UTC, and 80% at 2012 UTC.  The experimental data along with all radar tilts analysis helped forecasters increase lead-time and confidence in issuing a severe thunderstorm warning.  After the warning was issued the storm again experienced a lightning jump and ProbSevere values maxed at 100%, with MRMS MESH over 3.00″.

KSJT 0.5 degree reflectivity, NOAA/CIMSS ProbSevere contours and experimental severe thunderstorm warning polygons valid 1948 - 2016 UTC 20 April 2016.
KSJT 0.5 degree reflectivity, NOAA/CIMSS ProbSevere contours and experimental severe thunderstorm warning polygons valid 1948 – 2016 UTC 20 April 2016.

-Sieglaff

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Prob Severe May Provide Better Lead Time

On the storm south of Fort Stockton, the prob severe values increased to >70% before significant depth of the 50 dBZ core above -20C was seen on radar. In the loop below the prob severe circles the MRMS 50 dBZ echo height above -20C. Notice the higher values in the pink color show up before significant 50 dBZ depth above -20C does. This suggests that the prob severe product may be able to provide lead time over legacy severe detection techniques such as the Donavon criteria for severe hail. Prob severe values are quite high on the storm to the north which had much less 50 dBZ core depth above -20C, although may still have met minimum severe thresholds.
probsvrani
UPDATE: At 5:50, golf ball size hail was reported with the northern storm. This encouraging. Perhaps the false alarms from prob severe are relatively minimal. This is something that I am particularly interested in assessing throughout the rest of this experiment. Prob severe reached >70 approximately 16 minutes before my warning threshold was reached using MRMS 50 dBZ depth above -20C. If assessing with All-Tilts on a single radar I may have caught it and decided to warn a few minutes earlier though. Still, two cases suggest prob severe offers better lead time. Another cell was clearly non-severe based on radar assessment in eastern Ward County moving into Crane County. Prob severe values remained low with this storm, further supporting the suggestion that prob severe may offer better lead time with relatively low false alarms. Prob severe seems to be performing much better in this environment characterized by stronger deep layer shear as compared to yesterdays low-shear / high-CAPE environment in South Texas.

-dryadiabat

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Another storm in Midland WFO

Just to the northwest of the today’s first big storm, another storm developed in Pecos County, TX.  The NOAA/CIMSS ProbSevere model provided a large amount of lead-time and the forecasters said, “…we were looking a suite of experimental products and had we been more focused on ProbSevere, we would have likely issued the warning even earlier…”  Below is a loop of select times between 2134 and 2224 UTC 19 April 2016 (Figure 1).

Select times between 2134 and 2224 UTC 19 April 2016 NOAA/CIMSS ProbSevere, KMAF 0.5 degree reflectivity, and experimental severe thunderstorm warnings.  The storm of interest has the readout displayed (northwestern storm).
Select times between 2134 and 2224 UTC 19 April 2016 NOAA/CIMSS ProbSevere, KMAF 0.5 degree reflectivity, and experimental severe thunderstorm warnings. The storm of interest has the readout displayed (northwestern storm).
At 2136 UTC the ProbSevere values jumped from 26 to 63% due to strong satellite normalized vertical growth rates and increase of MRMS MESH from 0.51″ to 0.75″.  The ProbSevere values fluctuated slightly, largely in the 60%s until 2210 UTC when the probability then increased over 80%.   By 2224 UTC ProbSevere was 97% for this storm and an experimental severe thunderstorm warning was issued.

UPDATE:  Despite the very rural region, a golf ball sized hail report was received at 2250 UTC with this storm.

-Sieglaff

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