Performance of the Navy’s Tropical Cyclone Prediction Model in the Western North Pacific Basin during 1996

Abstract

The U.S. Navy?s operational implementation of the hurricane prediction system developed at the National Oceanographic and Atmospheric Administration?s Geophysical Fluid Dynamics Laboratory is described, and the performance of the model during the 1996 western North Pacific tropical cyclone season is analyzed. The model was highly reliable in terms of maintaining and tracking tropical cyclones, maintaining 96%, 93%, and 93% of all tropical storms and typhoons at 24-, 48-, and 72-h forecast periods. Subsequent model improvements raised these percentages to 96%, 93%, and 100%. Overall track errors were 176, 316, and 466 km for the same periods. Errors for tropical storms and typhoons were 75?150 km smaller than those for tropical depressions. The difference generally grew with forecast length. Large track errors were generally associated with a sheared environment, spurious interactions with elevated terrain, or poorly timed recurvature. On average, the model slightly underforecast intensity, but intense systems were significantly underforecast due to the inability of the model to resolve the eyewall. For the entire season, tropical cyclone track errors are very similar to those of the navy?s global model, Navy Operational Global Atmospheric Prediction System. However, significant differences are found in individual forecasts. Further study is required to identify environmental features that lead to systematic differences in model performance.