Explosive growth in Missouri

A storm southwest of St. Louis, Missouri exhibited very strong satellite growth rates, nearly 30 minutes prior to robust radar development. ProbSevere showed an increase in MESH from 0.08" to 0.99" and an increase in flash rate from 2 to 48 flashes/min from 20:02 to 20:04Z. This jumped the ProbSevere value from 11% to 94% in a very high MUCAPE / moderate effective shear environment. Without the strong satellite growth rates, the probability likely would have been in the 50% range as opposed to 90%. This case also demonstrates what forecasters at HWT have repeatedly said, that a large jump in probability often highlights a developing strong or severe storm.

Fig. 1: ProbSevere contours, MRMS composite reflectivity, GOES-East visible reflectance, and official NWS severe thunderstorm warnings.