Hail Methodology

How hail values shown in address, hail explorer, and PDF weather reports are derived.

The one-sentence version

StormAuditor describes hail at an address using radar-estimated hail size (NOAA MRMS MESH) at and around the property, cross-referenced with NWS warnings and Local Storm Reports, and reports the result as an estimate with its distance context.

How SAHE-2 works

Radar coverage is not uniform: in parts of the intermountain West the nearest NEXRAD beam overshoots low storms, and at long range everywhere the beam samples higher in the storm — both reduce hail-detection accuracy, so an absence of radar-estimated hail in radar-sparse areas is weaker evidence than the same absence near a radar site.

Reported hail sizes are the algorithm's actual output values, unrounded — a value of 0.59 in. is exactly what the radar algorithm computed for those coordinates, not a value rounded toward a marketing bin. Treat the size class (sub-severe, severe, significant) as the robust signal and the decimal as the algorithm's best point value.

MESH is a radar-derived estimate of the maximum hail size aloft on a roughly 1-km grid. The engine samples MESH at the property and in expanding distance rings, so a report can honestly distinguish "radar estimated 1.25 in. over the property" from "radar estimated 1.25 in. about 2 miles away." NWS severe thunderstorm warnings document forecaster expectations in real time, and Local Storm Reports capture what people measured or observed on the ground. The three lines of evidence are presented together, never silently merged.

What hail values mean — and don't

Radar estimates size aloft; what reaches the ground can differ, and melting, wind, and storm motion matter. A large MESH value near an address raises the plausibility of hail at the address; it does not prove impact, and absence of reports does not prove absence of hail. StormAuditor never converts a radar estimate into a damage conclusion.

Where hail data appears

The statewide Hail Explorer maps swaths by date, Hail Report by Address and Hail History cover single properties, and the free Hail Size Guide visualizes sizes from pea to softball. Sources are documented on Data Sources; caveats on Limitations.