DISCUSSION
The P1 values of nearly unity shown in dashed line (panel e) indicate that the solar wind (SW) event being encountered at a given time is a positive Bz (therefore nongeoeffective) event but that it is a long-duration Bz > 0 event to be followed by a geoeffective Bz < 0 event of comparable duration (tau) and magnitude. This means that the current SW is nongeoeffective but a storm is predicted to occur at a time approximately tau (e.g., 20 - 30) hours from the time of prediction. Thus, it should be interpreted as a "storm watch." The dotted line means that the positive Bz (nongeoeffective) event is not to be followed by a geoeffective Bz < 0 event of comparable duration and Bz magnitude. Thus, the dotted lines mean no storms in sight. The classification is determined by the value of Bym/Bzm [ Chen et al., 1997]. In this event, both Bz and By fluctuate significantly, and the classification fluctuates between geoeffective and nongeoeffective classes. However, no actual prediction of imminent storm (P1 > 0.5 in solid lines) is generated. Thus, the dashed-line portion of P1 represents a misclassification but does not lead to an alarm (solid lines).