Forecast statistics for “sudden” geomagnetic storms. (a) Storm predictions using real-time data input. (1) final Dst_p; (2) the earliest prediction of both upper and lower limits of Dst_p within 25% of actual storm magnitude; (3) the earliest prediction of Dst_p with 3-hour forecast (not “sudden” in real-time); (4) and (5) the predictions of Dst_p, which were out of 25% range from actual Dst_p. (b) Storm predictions using final data input. (6) final Dst_p; (7) the earliest prediction of both upper and lower limits of Dst_p within 25% of actual storm magnitude; (8) the predictions of Dst_p, which were out of 25% range from actual storm magnitude. (c) The advance warning time (in hours) of the Dst_p forecast using real-time input.