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Improvement of Tropical Cyclone Track Forecasts

From 1 June 2004, JMA narrowed probability circles* for the tropical cyclone (TC) track forecast. This improvement is based on the verification results of the recent TC track forecasts.

* A circular range into which the tropical cyclone is expected to move with the probability of 70% at each validation time

The verification of our forecasts from 2001 to 2003 indicated the feasibility of reduction in the radii of the probability circles by about 10% on an average compared to the previous ones, in particular 25% for TCs with the movement speed of more than 15kt (Fig.).

The narrowed provabiliy circle is expected to allow disaster prevention activities to be more effectively coordinated.

1 June 2004
    Fig.: Example of the improvement of the TC track forecast

This shows a comparison of the new probability circle with the old one in the case of a track forecast of TY ETAU (0310) issued at 12UTC 6 August 2003. The red solid circles indicate new probability circles, and the blue dashed ones describe old probability circles.