MESH
Definition
- Related pages
- 6
- Last revised
- 23 August 2026
MESH is a size of hail inferred from radar. A weather radar does not see hailstones; it measures how strongly the air above a point returns its signal, at a series of heights. The algorithm takes the part of that return that sits above the freezing level, where the return is most likely to be ice rather than rain, weights it by how far above freezing it is, and converts the total into the largest stone the storm could plausibly have produced over that point. The figure is computed for every cell of a grid, every few minutes, for the whole country, whether or not anyone was standing there.
That reach is the point of it and also its limit. It is the only kind of evidence that covers ground nobody reported from, and it is the basis of the hail swaths drawn on a map. But it is an estimate of what the storm was capable of, not a record of what fell: melting on the way down, the wind, the angle of the beam and the distance from the radar all sit between the signature and the ground. A large figure over a point is a reason to look; it is not a measurement at the point.
The product therefore files it on the detected side of the line and keeps it there. A radar-derived size is an analysis: it is drawn as a hollow mark, set in the estimated tone and qualified as analyzed wherever it is printed, while a ground measurement is drawn as a filled mark and set in the observed tone. The two are never added together, never averaged, and never presented as corroborating each other beyond the fact that both are on record for the same day near the same place.
In the report
How the document prints it
In the report a radar-derived size appears as a gridded analysis, qualified as analyzed wherever it is printed, with the date, the time and the grid cell it was computed for, and it is kept in its own column apart from anything measured on the ground. The hail swath on the map is drawn from it, and the map says so. Where a person or an instrument also measured hail on the same day, the report prints both figures side by side with each one's source, so a reader can see how far the estimate and the measurement were from each other without either being adjusted toward the other.
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
Radar detection
A hail, rotation or tornado signature an algorithm flagged in one radar's sweep at a recorded time and place, logged as an instrument's observation.
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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 swath
The area a storm is estimated to have dropped hail of a given size over, drawn on a map from radar analysis or traced between ground reports.
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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
Measured and detected: radar hail sizes against spotter reports
The record keeps a stone measured on the ground apart from a size computed from radar, because a court will ask which is which. This guide names the kinds of evidence as the report names them, states what a radar-derived size can and cannot say, explains why a measurement is drawn as a filled mark and a detection as a hollow one, and shows how to read the two on the same day.
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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.
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. Ready in minutes.
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 observers cover some areas better than others, sources revise their records, and recent reports can take weeks to arrive and settle. Coverage also thins as the years go back: an early quiet stretch may describe who was watching rather than what the weather did. 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.
A record sits where its source filed it. Reports made from the ground are commonly logged against a town, a landmark or an offset from one rather than the spot where the measurement was taken, so any distance shown for one carries that source's own location error. Radar detections and warning geometry are instrument-located and do not.
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.