Radar detection
Definition
- Related pages
- 5
- Last revised
- 23 August 2026
A radar detection is an entry in the federal inventory of signatures the radar network's algorithms raised: a storm cell whose reflectivity above the freezing level implied hail, with a probability and an expected largest size; a mesocyclone, a region of persistent rotation; a tornado vortex signature, a tighter rotation near the ground. Each is fixed to the radar that saw it, the time of the sweep and the position of the cell, and kept whether or not anybody on the ground reported anything.
A detection attests that at that time an instrument recorded a storm with that signature over that point: an observation by a machine, contemporaneous and geolocated, which is why it is filed on the observed side of the line. What it does not attest is what fell. The size attached to a hail signature is the algorithm's expected size, not a measurement; the storm may have been producing hail aloft over ground where nothing fell, and a signature some minutes apart from a ground report may be the same storm or the next. A detection says where to look and when.
The product draws the line here. A radar detection is an observation and is drawn with a filled mark, because an instrument made it at a time and place. A radar-derived size, computed over a grid from the same sweeps, is an analysis drawn with a hollow mark. Both come from the same radars; only one records a particular storm at a particular moment, and only that one is called a detection.
In the report
How the document prints it
In the report a radar detection is a row in the record table with its date, its time, its signature and its distance and bearing from the address, marked as measured, and its citation under Sources and method names the inventory it came from and the tight radius it was searched at, because a detection is precisely located. In the findings it is one kind of evidence, a radar detection, counted beside a ground observation and an official warning when confidence is graded; a finding resting on detections alone is a single kind, however many there are.
From the record
Radar detections in the record
- Independent radar sources
- 1
- Searched nationally
- 0
- Settled record from
- Fills when an address is run
- All independent sources
- 9
The record draws radar detections from one independent source, searched around each address when its report is run. Each detection is an instrument's observation at a time and a place, filed as measured; the radar-derived sizes on the same days are analyses, and are filed apart from it.
Measured Detected, not 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
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
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
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
Independent source
A record-keeping route by which a storm reached the archive, counted once however many rows it produced, so that agreement between routes can be measured.
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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.
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
- Drawn from the archive when the page was compiled, 24 August 2026, and rebuilt daily as the record deepens. Every figure in the panel marked From the record is computed, not written, and links to the page it came from.
- 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.