A History of Western North Pacific Tropical Cyclone Track Forecast Skill

Abstract

The tropical cyclone (TC) track forecasting skill of operational numerical weather prediction (NWP) models and their consensus is examined for the western North Pacific from 1992 to 2002. The TC track forecasting skill of the operational NWP models is steadily improving. For the western North Pacific, the typical 72-h model forecast error has decreased from roughly 600 km to roughly 400 km over the past ten years and is now comparable to the typical 48-h model forecast error of 10 years ago. In this study the performance of consensus aids that are formed whenever the TC track forecasts from at least two models from a specified pool of operational NWP models are available is examined. The 72-h consensus forecast error has decreased from about 550 km to roughly 310 km over the past ten years and is now better than the 48-h consensus forecast error of 10 years ago. For 2002, the 72-h forecast errors for a consensus computed from a specified pool of two, five, seven, and eight models were 357, 342, 329, and 309 km, respectively. The consensus forecast availability is defined as the percent of the time that consensus forecasts were available to the forecaster when he/she was required to make a TC forecast. While the addition of models to the consensus has a modest impact on forecast skill, it has a more marked impact on consensus forecast availability. The forecast availabilities for 72-h consensus forecasts computed from a pool of two, five, seven, and eight models were 84%, 89%, 92%, and 97%, respectively.