Warnings
How Tornado Warnings Are Issued: Radar, Spotters, Rotation, Debris, and Warning Polygons
How tornado warnings are issued using radar rotation, debris signatures, spotter reports, storm environment, and warning polygons.
Quick answer: Tornado warnings are issued when radar, reports, or storm evidence indicates a tornado is occurring or likely soon.
Radar clues
Meteorologists look for rotation, storm structure, debris signatures, and trends over time.
Velocity data is especially important.
Reports
Trained spotters, emergency managers, law enforcement, and public reports can confirm what radar suggests.
Reports may arrive after the storm is already dangerous.
Warning polygons
Warnings are drawn for areas expected to be at risk, not entire counties by default.
If you are in the polygon, shelter immediately.