Historical radar, by date and time
Retrieve any WSR-88D scan back to 1991, at the resolution it was recorded. Every elevation, every product. Free, without an account.
Coverage
- Period
- 1991 to the present, for the roughly 160 radars covering the United States and its territories. Each site begins when it entered service.
- Resolution
- A sample every 250 m along the beam, at 0.5° azimuth spacing and 0.25° on the lowest elevations. Not the reduced Level III product most radar sites display.
- Products
- Reflectivity, velocity, spectrum width, correlation coefficient, differential reflectivity and differential phase, where the radar recorded them.
- Elevations
- Every angle in the volume scan, which allows the vertical structure of a storm to be examined rather than only its base.
- Comparison
- Up to three products side by side on the same moment, panning and zooming together with a shared cursor readout.
Retrieving a past storm
- Enter the date and time. Within an hour is close enough; the timeline then steps scan by scan.
- Select the radar. The nearest site is usually correct. At 60 miles the beam samples the middle of a storm. At 150 miles it overshoots most of it.
- Step through the volume scans. A WSR-88D completes a volume every four to six minutes in precipitation mode, so a tornado's full track is a few dozen scans.
- Change products. Reflectivity locates the precipitation, velocity resolves rotation, and correlation coefficient identifies lofted debris.
Why resolution matters in an archive
Most archives of past radar hold images of radar: a rendering made at the time, at whatever resolution and colour scale was chosen then. This archive holds the measurement, so a scan from 2011 can be rendered now in any product the radar recorded, at the resolution it was recorded.
That distinction matters for the cases people usually need it: establishing where a hail swath fell, determining whether a storm was rotating before damage occurred, or documenting a debris signature. Each requires the underlying samples rather than a picture of them.
Common questions
How far back does the archive go?
To 1991 for most sites, when the NEXRAD network was being installed. Coverage varies by site: a radar commissioned in 1994 has nothing before 1994, and individual days are missing where the public archive has gaps.
Is it free?
Yes, and no account is required. The archive is public data published by NOAA.
Why does an older scan have fewer products?
Dual-polarisation, which produces correlation coefficient and differential reflectivity, was fitted to the network between 2011 and 2013. Earlier scans carry reflectivity, velocity and spectrum width only. Super-resolution arrived in 2008, so scans before it are coarser.
Can I link to a specific moment?
Yes. In the archive the address bar carries the radar, the products and the moment, so the URL reproduces exactly what is on screen.