Errors in arrival time predictions. (a) Travel time errors (predicted – observed arrival times) ordered by increasing longitude. The numbers on the abscissa are the event numbers in Table 3. Green stars: SXR proxy. Red squares: ϕ_9 GHz. Blue circles: LASCO coronographic observations (V_EXP = 2V_CAT). The red lines mark the ±12 h error window while the black vertical lines, the interval between the shock and ICME arrivals. (b) Correlations between observed and predicted travel times.