Masayuki Nakagawa
Numerical Prediction Division, Japan Meteorological Agency

    The Japan Meteorological Agency (JMA) upgraded the resolution of the Global Spectral Model (GSM) from TL319L40 to TL959L60 on 21 November 2007, when the Typhoon Model retired from operational use. Since then, tropical cyclone (TC) track and intensity forecasts have been supported by GSM only. GSM provides numerical weather prediction (NWP) products four times a day for all TCs existing globally. This paper gives an outline of the high resolution GSM and shows its performance in TC track and intensity forecasts.

Munehiko Yamaguchi
Rosenstiel School of Marine and Atmospheric Science, University of Miami

Takuya Komori
Numerical Prediction Division, Japan Meteorological Agency

    The Japan Meteorological Agency (JMA) began operation of a new Ensemble Prediction System (EPS) known as the Typhoon EPS (TEPS) in February 2008. TEPS has been designed to improve track forecast targeting for tropical cyclones (TCs) in the Regional Specialized Meteorological Center (RSMC) Tokyo - Typhoon Center's area of responsibility within the framework of WMO. It runs up to four times a day with a forecast range of 132 hours. The ensemble size is chosen as 11, and a singular vector method is employed to make initial perturbations.
    The results of TEPS verification during a quasi-operational period from May to December of 2007 showed that ensemble mean track forecasts have a statistically better performance than deterministic forecasts under non-perturbed runs; the error reduction is 40 km in five-day forecasts. Moreover, there is a strong spread-skill relationship between the position errors of the ensemble mean and the ensemble spreads of tracks, indicating that TEPS would be useful in representing the confidence level of TC track forecasts.

Masakazu Higaki, Hironori Hayashibara, Futoshi Nozaki
Office of Marine Prediction, Japan Meteorological Agency

Japan has suffered many storm surge disasters in the past, especially those associated with tropical cyclones (TC). To mitigate the effects of such disasters, the Japan Meteorological Agency (JMA), which is responsible for issuing storm surge warnings, operates a numerical storm surge model to provide the basis for warnings. The model runs eight times a day and provides 33-hour predictions of storm surges and sea levels for 290 points along the Japanese coastline. When a TC enters the vicinity of Japan, the model predicts multiple scenarios of storm surges with different meteorological forcing fields to take into account the uncertainty in TC track forecasts.