tinychaseTornado kiosks · tornado warnings, 2008 to 2025
The Warning Gap
A tornado warning is a promise of minutes. This joins every tornado to every NWS warning polygon in force at the moment and place it touched down, and asks two things: was there a warning, and how much time did it buy? The answer to the first has been stable for fifteen years. The answer to the second changed in 2012, and never changed back.
Minutes between warning and touchdown, every warned EF1+ tornado
Half of warned tornadoes arrive within 14 minutes. One in seven arrives with five or fewer. Four in ten arrive with no warning at all.
What changed in 2012
Warned share and false-alarm ratio by year, then median lead time. Tap a year.
Where the minutes go
Median lead time for warned EF1+ tornadoes, by state, 2008 to 2025. Tap a state.
Stronger is better warned
The strongest tornadoes are almost always warned, with more lead. Weak ones are a coin flip.
Night is not the problem
Nocturnal tornadoes are warned at least as often, with the same lead. The deaths come from what people do with the minutes, not whether the minutes exist.
Data: TerraPulse tor and nws_warning dexes (SPC/NCEI tornado records; NWS VTEC tornado warnings via the Iowa Environmental Mesonet archive), exported 2026-09-12. A tornado counts as warned if its touchdown point lies inside a tornado-warning polygon whose issue and expiry times bracket the touchdown time; lead time is touchdown minus issuance. This is stricter than official NWS verification, which credits a warning anywhere along the track and allows a short grace window, so warned shares here run about 15 points below published probability-of-detection figures. A warning counts as verified if any rated tornado touched down inside it while in force. Storm-based polygon era only (October 2007 onward); 2008 to 2025. County-based warnings and tornadoes lacking a rating are excluded.