Every day, each Stormycast forecast is checked against the storm reports that came in: a report within 25 miles (40 km) of a point during the day, at 3,529 points across the lower 48 US states, from NOAA's Storm Prediction Center. SPC's own 13Z day 1 outlook is scored the same way beside it.
Caught and came true
Caught: of the reports, the share inside an area forecast at that level or higher. Came true: of that area, the share where a report came; for a well-made forecast it is at least the level.
Forecast against what happened
Each band of forecast chance (across) against how often a report came there (up). On the dotted line, a 10% forecast happens 10% of the time.
Skill by day ahead
Brier skill against always forecasting the average (0); higher is better. Stormycast's 00Z runs; SPC's 13Z day 1 for comparison.
Day by day
Tested before launch
Before going live, day 1 was checked over the US on past days against Nadocast, a published machine-learning outlook (it stopped in November 2026 when the models it ran on were retired). These checks were made on the parts separately; the live forecast mixes them.
Disclaimer
Stormycast is an experimental, automated forecast made by a computer model. It is not an official forecast or warning, and no forecaster checks it before it is published. It can be wrong, late or missing.
For anything that affects safety, follow your national weather service and local authorities: in the US, the National Weather Service and its Storm Prediction Center.
The model learnt from US storms. Elsewhere its chances have not been checked against local storm reports, so treat them as a rough guide only.
Stormycast is not affiliated with or endorsed by NOAA, the National Weather Service, the Storm Prediction Center, ECMWF or any other weather service. The forecasts are provided as they are, without warranty of any kind, and their makers accept no liability for how they are used.
Past scores do not promise future ones. Scores here cover the lower 48 US states only, against preliminary reports, which are incomplete and sometimes misplaced.
Stormycast by stormy_sound, Nexradar · not an official forecast · reports: NOAA/SPC (preliminary; EF2+ tornadoes are not scored live, as early reports seldom carry a rating).