StormProof → guides → Radar-estimated hail vs ground reports: what each proves

Radar-estimated hail vs ground reports: what each proves

Radar products (like MESH, maximum estimated size of hail) infer hail aloft from reflectivity — continuous coverage, no observer needed, but an estimate of what the storm could drop, not what reached the ground. Ground reports document what actually fell at points — sparse, observer-dependent, but observations. Commercial hail maps are largely radar inference tuned against ground truth.

For claims, the hierarchy is: ground reports anchor (they are official records with narratives); radar fills spatial gaps between points and supports "the swath passed over the address" arguments; and any radar-derived claim should be labeled as estimated. A report that silently mixes the two invites the cross-examination it deserves.

The hail map shows my address in a swath but there is no nearby report. Did it hail?

Possibly — swaths between report points are exactly where radar adds value, and rural reports are sparse. But the swath is an estimate. An honest file says: radar-estimated hail of X at the address; nearest ground observations Y at Z miles; absence of a point report does not prove absence of hail.

Why do commercial hail maps disagree with each other?

Different radar algorithms, calibration choices and smoothing. The underlying NWS ground reports are the shared, public reference — which is why our products cite reports and label everything else by provenance.

Is NEXRAD data itself official?

The radar data is official NOAA data; hail size derived from it is a model output. "Official" attaches to the measurement, not to every inference layered on it.

Sources and standing caveat

Official records referenced throughout: NCEI Storm Events Database (the official NWS storm record, 1950–present) and SPC daily storm reports (preliminary, same-day). NWS records are point and path observations. The absence of a nearby report does NOT prove that no hail fell at this address — it means no observation was logged nearby. A report of nearby hail documents the event; it does not by itself prove damage to a specific structure. Nothing on this page is legal, insurance, or public-adjusting advice — deadlines, coverage and remedies are policy- and state-specific.

Put the record in the file

A per-address verification report compiles every NWS-recorded hail and wind event within 1, 3 and 10 miles of any US address — distances, official narratives, citations, provenance labels — formatted as an insurance-appeal attachment, hosted on HailEvidence (the neutral evidence surface).

Unlimited reports — Pro $99/mo Single report $29