Prob. Severe Model and Dual-Pol

Posted in General on by Darrel Kingfield.

The prob. severe model has been a great way to grab attention to storms that need to be monitored for the developing convection over the northern DVN CWA. Taking a look at how well it verified with dual-pol products and spotter reports, this screen capture (below) shows the prob. severe model overlaid on ZDR (upper right) and then 0.5 base reflectivity in the upper left, KDP on the lower left, and CC on the lower right. Based on the severe prob (shows 94% at 2138Z), my partner issued a Severe Thunderstorm Warning ten minutes prior to this screen capture as the probability trend was increasing over time. Having the ability to look at the parameters detailing more specifics about what the model is analyzing is very helpful in maintaining awareness with a particular storm. The MUCAPE (2325 J/kg, shown) and effective bulk shear (50.3 kts., also shown) being consolidated into one quick click of a mouse is much faster and easier than going to pull up the RAP elsewhere and analyzing the local storm environment. One other parameter that might be helpful is effective SRH. As for the other current, existing parameters, the same could be said as the other two above: the MRMS MESH, while overdone, provides an opportunity to monitor trends; and the satellite progs with annotations indicating whether or not the vertical growth rate and glaciation rate is moderate, strong, etc. is helpful and allows for increased confidence when utilizing this tool with other, more traditional methods. Without knowing how the exact values with respect to the satellite-tracking rates translate to growth/decay, the annotations deciphering what the values mean is critical to understanding the storm’s trend.

2138Z_ProbSvrwithDualPol_cropped

Comparing the prob. severe outline with the storm in question, dual-pol showed KDP values that were blacked out (with surrounding pixels well above 1), CC values below 1 (~.8 to .9), and a small but still evident three-body scatter spike. DVN received a report on this storm just two minutes later that was close to severe criteria:

LSRDVN

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
445 PM CDT TUE MAY 20 2014

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0440 PM     HAIL             2 W DUBUQUE REGIONAL AI 42.40N 90.75W
05/20/2014  M0.88 INCH       DUBUQUE            IA   EMERGENCY MNGR

            PEA TO NICKEL SIZE HAIL REPORTED ON HIGHWAY 151.

&&

Ten minutes later, another report of hail over severe criteria was issued from DVN, verifying my partner’s warning, the prob. severe model, and what was seen in radar trends:

LSRDVN

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
457 PM CDT TUE MAY 20 2014

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0450 PM     HAIL             1 E DUBUQUE REGIONAL AI 42.40N 90.70W
05/20/2014  M1.50 INCH       DUBUQUE            IA   EMERGENCY MNGR

&&

Overall and so far, this tool is a great resource and would be good to have in the toolbox.

~Linda

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