Hail swath
Definition
- Related pages
- 5
- Last revised
- 23 August 2026
A hail swath is the footprint of a hailstorm drawn as an area: the ground over which the evidence places hail at or above a given size. Hail falls from a moving storm in a band a few miles across and tens of miles long, and the swath is the band, shaded by size, with the larger thresholds nested inside the smaller. It answers what no single report can: where the hail fell between the points anyone reported from.
Where the swath comes from decides what it can claim. Since the national radar mosaic became available, a swath is contoured from the radar-derived hail size over every cell of the grid, which gives it detail and reach but makes it an estimate everywhere, including over the cell containing a property. Before that, a swath can only be interpolated between ground reports, and a shape drawn between points nobody stood between is a weaker claim still. Either way the edge of a swath is not a line somebody measured; it is where the estimate crosses a threshold, and a roof just outside it was not found to be clear of hail.
The product draws every swath as an estimate and says so. The edge is dashed, the bands are named for the objects on the spotter chart, and each swath records which method drew it. A ground report inside a swath and the swath are two objects: one measured at a point, one inferred over an area, and the product never merges them into a single figure.
In the report
How the document prints it
In the report the swath is drawn on the storm map, nested by size band with a dashed edge and a key naming each band and its threshold, and the map states whether it was traced from the radar analysis or interpolated between reports. The address is marked on the same map, so a reader sees whether it lies inside a band and which, without the document saying what that means for the roof. Where the analysis was read over the address, the size is printed as a gridded analysis, qualified as analyzed and drawn with the hollow mark, in its own column apart from anything measured.
Related
The terms this page uses and the guides that go further. Each is shown against its own example from the record.
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Term
MESH
A radar algorithm's estimate of the largest hail a storm could have produced over a point: an analysis, detected and not measured, never a measurement.
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Term
NEXRAD
The national network of Doppler weather radars operated by NOAA and its partners, from which every radar-based figure in the record is derived.
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Term
Hail size
The diameter of the largest hailstone at a place, reported in inches or by the named object on the spotter chart it was compared with.
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Guide
How far away a hail report can be and still count
A hail report is a point: where a person stood, or where a radar placed a signature. A property is another point. The distance between them is the first thing a reader checks and the first thing a reader misreads. This guide states what a distance establishes, how the report bands it, and why a record filed to a county cannot be measured from at all.
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Guide
How to read a hail report: what each figure means
A hail report is a list of records with figures attached, and every figure on it came from somewhere in particular. This guide walks the document in the order a reader takes it: the date and the window searched, a measured size beside a detected one, the distance and bearing from the address, the count of independent sources, and the line at the end that says what the report does not claim.
Sources
The primary references. Each opens on the agency's own site.
The glossary defines the word. The report is what uses it.
Everything above is definition: what the word means in the document, and what it does not. None of it says what reached one roof.
Run the address and the archive is searched at the property: the storm, the date, the measured size, the distance and bearing from the roof, and the federal record each figure came from, in a document that states its own method. About a minute.
How this page is made
- The text
- Written by the editors and last revised 23 August 2026. It explains the record and how the report reads it; it contains no figure of its own.
- The example
- The archive holds nothing this page could show yet, so no example is printed. One appears, computed rather than written, as soon as the record holds a relevant day.
- Measured and detected
- A report from a person or an instrument is measured. A radar-derived size is detected, not measured, and is marked as such, here and in every document we issue. The two are never added together.
- What this is not
- A definition of a word the report uses. It is not a report on any property, and it states no opinion about one. The coverage page states what the record holds, by kind and by year.
About this record
Everything here is reproduced from public federal and volunteer weather records, as the agencies and observer networks that publish them released it. Titan Weather compiles the record; it does not observe the weather, and it is not affiliated with any source it cites.
No archive holds everything. Storms cross places where nobody is standing, instruments and spotters cover some areas better than others, sources revise their records, and recent reports can take weeks to arrive and settle. Where this page shows nothing, nothing was found in the sources searched, within the period and area it states. That is not a finding that no weather occurred.
These pages describe the public record near a place or on a date. They do not establish what reached any particular property, and nothing here is insurance, legal or engineering advice.