GEFS-based U.S. Tornado Outbreak Synthetic Event Set

Global Ensemble Forecast System (GEFS) version 12 reforecasts computed tornado outbreak index. Part 1 of index is GEFS_POutbreak_daily_calib.nc, and part 2 of index is GEFS_US-num_daily.nc. The tornado outbreak index is described in Malloy and Tippett (2024) and post-calibration of tornado outbreak index is described in Malloy and Tippett (2025). If used, please cite dataset 10.5281/zenodo.15706145, and read/cite the accompanying publication(s) Malloy and Tippett (2026): https://doi.org/10.5194/egusphere-2025-3145 GEFS_POutbreak_daily_calib.nc First part of tornado outbreak index uses 6-hourly GEFS convective precipitation, storm relative helicity, and convective available potential energy to compute probabilities via logistic regression model, which is then aggregated as a daily maximum over the convective day (12 UTC one day - 12 UTC next day). Dataset dimensions: "time" = initialization time; length = 7294; start = 2000-01-01, end = 2019-12-31 "member" = ensemble member; length = 11; start = 0, end = 10 "step" = forecast lead; length = 34; start = 1 day, end = 34 days (This is the middle of the interval that aggregates over convective day 12Z-12Z, e.g., +1 day forecast initialized on 2000-01-01 is maximum tornado outbreak probability between 2000-01-01 12 UTC, 2000-01-01 18 UTC, 2000-01-02 00 UTC, and 2000-01-02 06 UTC, and the valid time would be labeled 2000-01-02 00 UTC.) "latitude"; length = 26; start = 50N, end = 25N (descending order) "longitude"; length = 71; start = 230, end = 300 (convert to standard system of coordinates by subtracting 360) GEFS_US-num_daily.nc Second part of tornado outbreak index uses GEFS daily probability maps from part 1 above, taking the map sum and grid cell maximum value of probability map to compute (expected) daily total U.S. tornado counts via negative binomial regression model. Dataset dimensions: "time" = initialization time; length = 7294; start = 2000-01-01, end = 2019-12-31 "member" = ensemble member; length = 11; start = 0, end = 10 "step" = forecast lead; length = 34; start = 1 day, end = 34 days