Abstract

Regression equations to forecast the movements and surface pressures of typhoons in the Western North Pacific were developed by the author in a paper at the Inter-Regional Seminar on Tropical Cyclones (Tokyo, 1962). In a statistical study based on the Veigas-Miller screening procedure used for forecasting Atlantic hurricane movement, three sets of regression equations were given. One used surface data exclusively, another used 700-mb data, and the third used both. These regression equations were derived from five years of data covering the period 1956–1960. The pressure pattern was obtained by using a grid of 91 points at intervals of 5 degrees of latitude and of longitude relative to the typhoon center. The set of equations for 12-, 24- and 48-hour forecasts has been computed.

After independent tests of this objective method were made during the 1961 season (as reported by Waldron) and during the 1962 season (as reported by Roper), the present author revised the procedure by stratifying the whole North Pacific into two zones, i.e., the “southern zone” for typhoons whose initial latitude is less than 26.9N and the “northern zone” for typhoons whose initial latitude is greater than 27N and less than 34N. Two acts of regression equations for these two zones were derived again. An independent test shows rather marked improvement in accuracy of forecast movement of typhoons in 1963.

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