Three-hour forecast (using model) showing (a) probability of geomagnetic storms, (b) K _p (22nd July–31st July, 2004) and (c) an illustration of the method to extract probability of storm occurrence for one prediction marked by vertical black line in panel (b). Black dashed lines in panels (b) and (c) represent the threshold K _p  = 5⁻, red and blue thin lines in panel (c) are observed K _p , and predicted mean respectively. Panel (b) is in the same format with Figure 7. The shaded region in panel (c) provides probability of geomagnetic storm (Pr[e] = 0.81, for details refer text).