A single severe thunderstorm formed in an environment with marginal effective shear (~35 kts) and MUCAPE (~1200 J/kg) yesterday afternoon in northern Georgia, traveling southward through the eastern suburbs of Atlanta. The storm produced between quarter-sized and golf-ball-sized hailstones and downed multiple trees and power lines.
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Figure 1: ProbSevere contours (pink is > 70%; gray is < 5%), MRMS MergedReflectivity, and GOES-16 visible reflectance.
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In the absence of strong environmental forcing, the ProbHail model is largely influenced by the MRMS MESH and ENI total lightning flash rate. The low wet-bulb 0C height (8500 ft) also contributed positively to ProbHail. Even in marginal environments with few storms, ProbSevere can still highlight potential threats.
The ProbWind model remained fairly low (≤ 40%), owing mainly to a weak 1-3 km mean wind and low-to-moderate MRMS AzShear values. Work is ongoing to improve ProbWind predictions in both wet and dry microburst environments.
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Figure 2: Time series of ProbSevere models for this storm, with corresponding severe reports and NWS warnings.
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Figure 3: Time series of select predictors and the maximum hazard probability (thick red line), with corresponding severe reports and NWS warnings.
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