Hail Swaths vs. Point Reports: Understanding Storm Data
By StormAuditor Editorial Team · Published 2026-07-22 · Updated 2026-10-07
Based on public NOAA and National Weather Service records, published under StormAuditor's methodology and data-source standards. Radar-derived hail sizes are estimates unless attributed to a ground report.
Damage-threshold ranges in this article are general guidance synthesized from industry and federal research — IBHS building-performance research, NWS severe criteria, and product standards such as UL 2218 (hail impact resistance) and ASTM D3161/D7158 (shingle wind ratings). Actual performance depends on product rating, age, installation quality, exposure, and impact characteristics — thresholds describe when damage becomes possible, not when it occurs.
Understanding whether a property was impacted by hail requires interpreting different types of storm data. Hail swaths, generated by radar, estimate hail presence and size across an area, while point reports are human observations of hail at specific locations.
Hail Swaths vs. Point Reports: Making Sense of Severe Weather Data
When you research past hail, you will meet two kinds of data: hail swaths and hail point reports. Property owners, contractors, adjusters, and attorneys all use them. Both help rebuild a storm's path and strength, but they hold different kinds of information. StormAuditor uses both for property-level research.
What Are Hail Swaths?
Hail swaths map where radar estimated that hail fell. Algorithms read radar reflectivity and other weather data to find hail in a storm and estimate its size and strength.
The Maximum Estimated Size of Hail (MESH) is a key part of these swaths. It comes from MRMS (Multi-Radar/Multi-Sensor) data, and StormAuditor uses it often. MESH gives each grid cell its own estimate of the largest hail expected at the ground.
- Pros: Swaths cover a whole area without gaps. They can estimate hail even where no one was watching. They show at high resolution where hail likely fell and at what estimated size.
- Cons: Radar estimates are not direct measurements. Weather conditions, radar beam height, and precipitation type all affect them. Radar can under-estimate wet hail. It can over-estimate where reflectivity is very high. Even so, MESH gives the best available estimate of hail across wide regions.
What Are Hail Point Reports?
Hail point reports are sightings of hail by people on the ground. They are sent to the National Weather Service (NWS) as Local Storm Reports (LSRs), and the Storm Prediction Center (SPC) compiles them. A report usually gives the time, the place, and the estimated size of the largest stone. Trained spotters, police, and the public send them in. They are invaluable for confirming severe weather.
- Pros: They are direct human sightings. They give solid evidence of hail at one place and time. They serve as ground truth and are key for checking radar estimates.
- Cons: They are local and sparse. A big hail event can happen with no one there to report it, leaving gaps. Judging hail size by eye can vary from person to person. Trained spotters use objects for scale, like quarters (1.00" across) or golf balls (1.75" across). One report shows hail at that spot only, not everywhere nearby.
How StormAuditor Shows Hail Data
StormAuditor puts both swaths and point reports into its historical hail reports.
- Radar first: Our hail method, SAHE-2, uses MRMS MESH as the main source for hail size and extent. The radar estimate is reported at a property when the address sits inside the ~1-km radar cell. Nearby cells are listed with their distance. These swaths give the widest area coverage available.
- Ground reports second: A hail report within 1 mile on the same date can set a higher value. Reports farther away are shown as context and do not change the estimate.
Together, these sources give a location-specific, traceable picture of past hail.
Practical Guidance for Property Owners, Contractors, and Adjusters
If hail may have hit a property, look at both swaths and point reports:
- Property owners: A StormAuditor report may show your property inside a strong hail swath, even with no point report nearby. That suggests hail very likely hit. Asphalt shingles often begin to show functional damage from hail 1.00" to 1.25" across. Metal roofs can dent from hail too small to fracture an asphalt shingle; whether a dent is cosmetic or lets water in depends on gauge, panel type, and condition. Window and skylight breakage becomes common at about 1.75" and larger.
- Contractors: Use swath data to target neighborhoods and properties that likely got hail. With point reports, it helps you rank inspections and gives context for damage assessments. Focus on the core of each swath and on places with larger estimated hail (1.00" or more).
- Adjusters: Swaths give the first geographic check on a claim: was the property inside a hail area? Point reports can back up or refine the radar estimate. A property in a warned area was under a warning, but did not always get the peak conditions. The combined swath and report data from StormAuditor shows where hail most likely fell.
Limitations
- Radar swaths, MESH in particular, can at times under-estimate wet hail or over-estimate where reflectivity is very high.
- Human reports depend on how many observers are around, and size is judged by eye.
- StormAuditor gives estimates, not measurements. We do not claim what caused specific damage. An on-site inspection by a qualified professional is the way to assess actual damage.
Related StormAuditor Tools
- Property-level Historical Weather Report
- Hail Explorer: State-wide MESH swaths + reports
- StormAuditor Wind Explorer
- Date-of-Loss Weather Research
- Our Data Sources
FAQ
Q: What is the difference between a hail swath and a hail report?
A: A hail swath is a radar estimate of where hail likely fell and how big it was. A hail report is a person's sighting of hail at one place and time.
Q: How does StormAuditor decide if hail hit my property?
A: StormAuditor reads the radar hail estimate (MRMS MESH) for the ~1-km radar cell your address sits in. A ground report within 1 mile on the same date can raise it. Nearby cells and farther reports are listed with their distance as context.
Q: Can hail swaths confirm property damage?
A: Swaths show the estimated presence and size of hail, so hail very likely fell in the area. But they are estimates. Only a qualified inspector or engineer can assess and confirm actual damage.
Q: What hail size does the NWS call severe?
A: The National Weather Service (NWS) defines severe hail as 1.00" (quarter size) across or larger.
Q: Can hail fall with no point report, or inside a weak swath?
A: Yes. Hail can fall where no one is watching, so no report is filed. Radar can also under-estimate hail size, mainly for wet hail or in complex storms. The swath can look weaker even when significant hail fell.
Q: What hail size often causes functional damage to asphalt shingles?
A: Asphalt shingles often begin to show functional damage from hail 1.00" to 1.25" across. Softer or older shingles can be damaged by smaller hail.