STATISTICS AND GEOGRAPHY OF TROPICAL CYCLOGENESIS IN THE EASTERN HEMISPHERE

A. V. Kislov

The vertical vorticity component computed from the 31-year NCEP/NCAR reanalysis data (2.5 ×2.5º) is used as a characteristic of tropical cyclogenesis in the northern part of the tropical Indian and Pacific oceans. The vorticity anomalies that differ from a mean by four standard deviations are used as a characteristic for storms and hurricanes. Interannual variability of the number of such anomalies correlates with the background conditions for El Nino (La Nina). A composite model of a tropical disturbance corresponding to the vorticity anomaly that exceeds four standard deviations has been developed. It is shown that the geostrophic components of the vorticity equation play the main role.