Tropical Cyclone Genesis in the Western North Pacific.
COLORADO STATE UNIV FORT COLLINS DEPT OF ATMOSPHERIC SCIENCE
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The paper presents climatological statistics on the location, frequency, and environmental conditions associated with seasonal tropical cyclone genesis of the western North Pacific. Data summaries are stratified into annual and monthly averages for the 28-year period of 1946-1973. The Annual Typhoon Reports of the U.S. Navy and Air Force from the Joint Typhoon Warning Center in Guam for the years 1949-1973 were used as the data source. It is observationally shown and physical reasons are given why seasonal cyclone genesis frequency is related to the product of the seasonally averaged parameters of 1 Low level relative vorticity, 2 the Coriolis parameter, 3 inverse of the vertical shear of the horizontal wind from lower to upper troposphere, 4 an ocean thermal parameter related to the sea surface temperature and the sea surface minus 200 feet sea temperature, 5 moist stability from the surface to 500 mb, and 6 middle tropospheric relative humidity. A western North Pacific seasonal forecast potential of cyclone genesis frequency is derived.