Everyday ProbSevere

As we wait for storms to get going in our CWAs of operation, storms are popping well to the east, in GA, VA, NC, and SC. Below are just two examples of ProbSevere highlighting developing convection in western Virginia and northeast Georgia. There is decent environmental shear in Virginia (~40 kts) and more marginal shear in Georgia (~25 kts). In both cases, the strong satellite growth rates and increasing MESH/total lightning flash rate steadily increase the probability of severe. However, forecasters should generally expect higher ProbSevere probabilities in higher shear environments. Functionally, this means a 40-60% probability might be as significant in a low/moderate shear environment as a 60-80% probability in a high shear environment (i.e., forecasters should not always expect a 80%+ probability on each storm that produces severe weather; a 30% probability should verify 3 out of 10 times, as well). One inch hail was reported 5 min after the warning in Virginia, and severe hail and wind damage were reported in Georgia about 40 min after the warning.

Fig. 1: A storm in western Virginia with strong normalized satellite growth and glaciation rates, which contribute to an increasing probability of severe up to 94% (in a well-sheared environment) before a severe thunderstorm warning.

Fig. 2: A storm in far northeast Georgia with one strong satellite growth rate and increasing MESH and flash rate in a moderate shear environment. The probability of severe on this storm increases to about 60% before a warning is issued.