IEM Daily Feature
Thursday, 27 May 2021

Spring SVR Warning Timing

Posted: 27 May 2021 05:49 AM

The past two overnights have seen thunderstorms visit the state with the storms from at least two nights ago necessitating the issuance of Severe Thunderstorm Warnings by NWS Des Moines. The featured chart presents the frequency of such warnings by time of during the months of April, May, and June. The chart nicely shows two peaks during the early evening hours around 6 and 9 PM. The 6 PM peak represents the peak of solar heating driving storms and the 9 PM peak is likely a complex relationship between storm upscale organization and people being awake to generate reports to help drive warning issuance. The minimum is shown around 8 AM, which is a time of peak stability after overnight cooling and just before any sunshine is able to drive an increase in instability.

Good = 11
Bad = 0