Competition rules
Scoring version S3 · schedule SCH1 · rating R1. Rules only change for future rounds; every round keeps the version it started with.
Every day
One round per UTC calendar day, every day of the year. Times are UTC and the server clock decides.
| Entry opens | 0000Z (forecast day) |
| Entry closes | 1600Z (forecast day) — the deadline instant itself is closed |
| Verification window | 1630Z – 1200Z (next day) |
| Preliminary results | 1800Z, day +2 |
| Final results (frozen) | 1800Z, day +7 |
You may revise your forecast as often as you like until the deadline; the last accepted version counts. Other players' forecasts are hidden until the deadline.
Your forecast
Will at least one qualifying tornado occur in the verification window? If you say YES, place a target inside the continental United States and give your timing. What you forecast depends on your division:
| Division | Which tornado is scored | Your timing | Timing points reach 0 at |
|---|---|---|---|
| Spotter | Any qualifying tornado (the one that gives you the best total) | A one-hour UTC window. t = hours outside your window (0 inside it). | 4 h |
| Chaser | Any qualifying tornado (the one that gives you the best total) | A 15-minute UTC window. t = hours outside your window (0 inside it). | 4 h |
| Forecaster | The first qualifying tornado of the period | The exact UTC time you enter for the first tornado. Early and late count the same: t = minutes off ÷ 60. | 1 h |
A qualifying tornado is an SPC preliminary (filtered) tornado report whose event time is inside the verification window and whose location is inside the lower 48 states or DC. Report data that is missing or damaged is never treated as "no tornadoes"; results wait until valid data arrives.
Scoring (maximum 100)
| YES, and a qualifying tornado occurs | 20 + location + timing, measured against your division's tornado (above) |
| Location | 55 × (1 − d / 150)², d = distance in statute miles (WGS-84); 0 beyond 150 mi |
| Timing | 25 × (1 − t / T)², t in hours as defined for your division, T = the limit in the table above; 0 beyond it. Timing points count only for a tornado within 150 miles of your target. |
| YES, no qualifying tornado | 0 |
| NO, and no qualifying tornado | 40 |
| NO, and a qualifying tornado occurs | 0 |
Location and timing points always come from the same tornado. Totals are rounded once to two decimals. Daily ties are broken by smaller distance, then smaller timing error; otherwise ranks are shared.
Divisions
Spotter, Chaser and Forecaster are competitive classes, not professional credentials. When you sign up you choose the division that fits your experience: Spotter if you are new to forecasting, Chaser if you chase, spot or follow severe weather closely, Forecaster if you are a meteorologist, a meteorology student or forecast for work. You may move up at any time, but never down.
Skill rating. Each final daily score is compared with a climatological reference forecast for that date, so days with many tornadoes and quiet "always NO" stretches earn little. Your rating is the average of that difference over your last 120 final rounds, weighted 75 % tornado days / 25 % no-tornado days and pulled toward zero when you have few forecasts. It is provisional until you have 20 final forecasts including 8 tornado days.
Promotion is automatic when your rating minus its uncertainty exceeds the next division's threshold (Chaser 4, Forecaster 10), when you finish in the top 5 % of your division 8 times in 30 rounds, or when you finish in your division's top three for a season. A promotion counts from the next round; points you already earned stay in your old division. At each season start, players whose rating is clearly below their division may move down one division.
Championships. To be ranked as a qualified season competitor in a division you need at least 15 scored forecasts there, covering at least half of the season's rounds since you joined it.
Seasons and standings
Seasons default to calendar quarters (Winter, Spring, Summer, Fall). Season, annual and all-time standings add up daily points; ties go to the higher average, then more days of 75+, then fewer forecasts. Official champions use final results only.
Fair play
Your forecast is your own work, and no one can use it to chase. Every player's target stays private until verification ends at 12Z the next morning, after the chase day is over. Only then do targets appear on the public maps and GeoFiles, next to the tornado reports and results. Before that, you are the only one who can see your forecast, through your private My Forecast link.
Players must be 18 or older. One account per person. No wagering, prizes or purchased advantages. Accounts used to avoid promotion or to manipulate standings may be suspended.