Turning wind near the ground
Rotation
Latest
How sharply the wind turns near the ground in each storm, in mph across a mile: where storms are rotating now.
-150150 mph a mile
Storm analysis / Turning wind, last hour
Rotation track, live radar analysis
Over DISCOVERY FARMS WATERWAY MT3 NEAR MILAN, Wisconsin, where the map opens. The whole country
The sharpest turning of the wind near the ground in the last hour, in mph across a mile: the path each rotating storm took. How to read it.
The rings are the storms the radars detect, the larger ring a severe one; each line runs to where its storm will be in an hour if it keeps its present speed and heading. Rotation and hail are what the radars detect and the analysis measures, not warnings: the official watches and warnings in force are drawn on the map in their own colours and set out in full under Alerts.
What the rotation track map shows
The sharpest counterclockwise turning of the wind near the ground at each place in the hour to each frame, in mph across a mile: the path each rotating storm has taken. A long, strong track is where a tornado was most likely, and where to look for damage.
How to read it
- Under 20 mph a mile
- Weak rotation.
- 20 to 40
- A rotating storm.
- 40 to 80
- Strong rotation; a tornado possible along the track.
- Over 80
- Intense rotation; the track of a likely tornado.
What it is for
- Find where a tornado may have touched down, and look there for damage.
- Follow a rotating storm’s path and judge where it is going.
- See the long tracks of a tornado outbreak.
How it is made
The storm analysis joins every radar in the national network every two minutes into one picture of the country on a grid about two thirds of a mile across, cleaned of ground clutter, birds and insects, and measures from it what no single radar shows: the largest hail, the turning of the wind, how high a storm’s heavy echo reaches above the freezing level, and what is falling, read with the temperature of the air. Storm Station keeps it every ten minutes for a day, the gauged rain and the radars’ view each hour, and draws it at every zoom from the analysis’s own grid.
A frame every 10 minutes, played as a loop of 1 to 24 hours. As data: /radar/now.json?show=rottrack, the times of its frames.
In the Field Book
Over a state
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With it
Severe AlertsWeather by stateForecast accuracyInstrument atlas
Beside it
Largest hail, last hour
Hail track
Latest
The largest hail of the last hour at each place, in inches across: the path each hail storm has cut.
.255 in
Reflectivity
Radar
Latest
Rain, snow and hail across the country now, from every radar in the national network, a new picture every five minutes.
1070 dBZ