26th Conference on Hurricanes and Tropical Meteorology


Performance of Navy's Global Model in Predicting Tropical Cyclone Formations in the Western North Pacific (Formerly Paper Number 1C.4)

Kevin K. W. Cheung, NPS, Monterey, CA; and S. C. S. Liu and R. L. Elsberry

In Cheung and Elsberry (2002, Weather and Forecasting), a set of criteria was developed to identify tropical cyclone (TC) formations in the Navy Operational Global Atmospheric Prediction System (NOGAPS) analyses and forecast fields. Then the NOGAPS forecasts of TC formations during 1997-1999 were verified. It was found that NOGAPS successfully predicted a formation within a maximum separation threshold of 4o latitude about 70%-80% for 24-h forecasts, but only about 20%-30% for 120-h forecasts. The number of false alarms (FAs) in the NOGAPS forecasts was also examined, and a large growth in FAs occurs between 24 h and 48 h before reaching a near saturation at later times. As a follow-up to this work, further verifications will be performed on NOGAPS during 2000-2003. This period is chosen because the Emanuel cumulus parameterization scheme replaced the Arakawa-Schubert scheme in NOGAPS during June 2000. Thus, a focus of this study will be the impact of this modification on NOGAPS predictions of TC formations.

Another improvement over the previous study is that a more sophisticated tracking algorithm will be used to examine the entire life span of the vortices instead of a single-time verification. An advantage of this approach is a more realistic account of the FA rate. As in Cheung and Elsberry (2002), detailed diagnostics of the failed prediction cases and FAs will be performed. Particular attention is paid to attributing the reasons of failed predictions and FAs to the model configurations and physics, and what characteristic synoptic patterns existed during these model failures.

extended abstract  Extended Abstract (200K)

Poster Session 1, Posters
Wednesday, 5 May 2004, 1:30 PM-1:30 PM, Richelieu Room

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