200 - Typhoon Committee

TCAR
CHAPTER 1 - TYPHOON COMMITTEE ACTIVITIES 2007
2007
e. Research Progress
Seasonal Prediction of the Tropical Cyclone Activity over
the Western North Pacific and the Korean Peninsula
Tropical cyclone is the most destructive natural
phenomenon in the world. To predict this destructive
tropical cyclone there have been many prediction
studies using a statistical model or a dynamical model.
A statistical model has been developed for the purpose
of predicting the seasonal activity of tropical cyclones
over the Western North Pacific (WNP) and the Korean
peninsula. The predictors are the number of tropical
cyclones (TC), tropical cyclones that exceed typhoon
strength (TY) and the overall TC activity index which is
referred to as Normalized Typhoon Activity (NTA) index
during summer period (June to August), fall period
(September to November), and over the whole year
(May to December).
Using the lag correlation among synoptic predictors such as sea surface temperature (SST) and mean sea level
pressure (MSLP) and the frequency of typhoon genesis, high lag correlation predictors used for statistical models
were selected. After making three sets of data based on closest months, highest correlation and subjective choice,
the prediction equations were derived by using selected predictors in the multiple linear regression applying the
30 year moving window method-after creating a prediction value, produces prediction value with a same method by
moving one year by one year, and the combination of independent variables with the lowest root prediction error of
sum of squares (RPRESS) from all the possible combinations was selected. In addition, to reduce the uncertainty of
forecast existing when predicting by a single prediction value, the ensemble model of 60 members for the frequency
of tropical cyclones was predicted by differentiating validation periods. From 1972 to 2004 typhoon data reported at
RSMC-Tokyo are used as variables. Using the data such as 500 hPa geopotential height, monthly sea level pressure,
SST, 850 hPa temperature, and 850 hPa meridian velocity from May 1971 to August 2004, 30 ensemble forecasts are
made for predicting typhoon activity. Fig. 2.27 shows the flow chart for processing the statistical model.
TC, TY, and NTA index are ensemble predicted by a statistical model in three summer months, fall months, and over
the whole year in WNP and TC that may affect over the Korean Peninsula is also ensemble predicted in three summer
and fall months. Table 2.4 shows the predicted TC, TY, and NTA over the western North Pacific and TC forecasts
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