Evaluating the ProbSevere Model in a Moderate Risk Event

The ProbSevere model was evaluated for a moderate risk situation on June 3, 2014. Storms across southern South Dakota and northern Nebraska were interrogated for severe potential, comparing warning timing and storm reports with the ProbSevere output. Overall, the ProbSevere model performed very well for the period of time that storms were analyzed. Storms consistently reach a ProbSevere level of around 90% around the time a warning was issued and well before reports were received.

Below are a few examples of how ProbSevere performed during the evaluation period.

The first storm that was analyzed ramped up quickly, reaching a ProbSevere level of 94% and maximum estimated hail size of 1.5" by 1407Z. The satellite growth rates were in the moderate to strong categories. This storm eventually dropped severe hail, with reports of 1" received at 1430Z and 1445Z, well after the model indicated a high probability of severe.

The second storm that was analyzed reached a ProbSevere level of 92% at 1456Z, holding around that level through 1520Z. The maximum estimated hail size generally ranged from 1.5" to 2.0" through the storm's peak intensity. A hail report of 1.75" was received at 1520Z, quite a bit after the model first indicated a high probability of severe.

The last storm that was analyzed intensified quickly. At 1412Z, the storm had a ProbSevere of only 14%.

By 1524Z, the ProbSevere had reached 90%, generally holding at that this level through 1610Z. The maximum estimated hail size ranged from 1.5" to 2.5". Severe hail reports of 1" were received at 1555Z and 1610Z, yet again well after the model first indicated a high probability of severe.

DDV
Forecaster
NWS Milwaukee/Sullivan

JLC
Researcher
UW-CIMSS