A simple statistical-synoptic tract prediction technique for western North Pacific tropical cyclones

A simple statistical-synoptic technique for tropical cyclone (TC) track forecasting to 72 h in the western North Pacific is derived. This technique applies to the standard (S) pattern/dominant ridge region (S/DR) and poleward/poleward-oriented (P/PO) combinations, which are the two most common and represent about 73% of all situations. Only eight predictors that involve present and past 12-h and 24-h positions, intensity, and date are used. The track predictions are simple to calculate and understand; are available in near-real time each 6 h; apply at all intensities, as compared to the complex global or regional dynamical model predictions that are only available each 12 h at about 3-4 after synoptic time; are not calculated for weak TCs; and tend to have accurate predictions only for tropical storm stage and above. The statistical-synoptic technique for S/DR cases has an improvement (skill) relative to the operational climatology and persistence (WPCLPR) technique of 12% after 12 h and 24% after 72 h if the TC remains in the S/DR pattern /region for the entire 72 h. The statistical-synoptic technique for P/PO cases have an improvement relative to WPCLPR of 11% after 12 h and about 13% for 72-h forecasts if the TC remains in P/PO for the entire 72 h. Assuming a perfect knowledge of the S/DR to P/PO and P /PO to S/DR transitions, a simple blending of a composite post-transition track with the statistical-synoptic technique is tested. For the 72-h forecasts initiated 12 h before the S/DR to P /PO transition, the statistical-synoptic track error is about 290 n mi (537 km) compared to 410 n mi (759 km) for WPCLPR. For corresponding P/PO to S/DR transition, the statistical-synoptic technique 72-h error is 215 n mi (398 km) compared to about 485 n mi (898 km) for WPCLPR.