ON TROPICAL CYCLONE ACTIVITY OVER THE WESTERN NORTH PACIFIC IN 2012

Tropical cyclone(TC) activity over the western North Pacific(WNP) in 2012 is summarized and the associated large-scale environmental conditions are discussed. In total 25 named storms formed in the WNP basin in 2012, among them were 3 tropical storms(TSs), 7 severe TSs, 4 typhoons, 6 severe typhoons, and 5 super typhoons. TC activity was close to a 30-year average but above the average active level of recent years since 2005. Total number of TCs formed in the South China Sea(SCS) in 2012 was below normal, with only 40% of the climatological mean. Overall, TC genesis over the WNP was characterized by four active periods. During each period TCs took distinct prevailing tracks. The periodic characteristics in TC genesis were attributed to the activity of the intraseasonal oscillation(ISO), while those in TC tracks were related to the large-scale dynamical and thermodynamic conditions induced by the enhanced WNP monsoon activity and the weak El Ni?o conditions.