Synoptic Climatological Characteristics of Explosive Cyclones over North Pacific in Winter

Based on analysis of 500 hPa synoptic maps associated with explosive extratropical cyclone activity over northwest Pacific in winter (from Dec. to Feb.) of 1975—1984, five synoptic patterns of extratropical cyclone development have been summarized in this paper, which are: North America High pattern (NAH), East Pacific High pattern (EPH), Mid Pacific High pattern (MPH), Berling Sea Blocking High pattern (BBH) and Pacific Low pattern (PL). The NAH and EPH patterns occur more frequently and last longer than others, and these two patterns cyclones tend to develop. This paper analyses further the tracking tendency of cyclones after their explosive development and concludes that: during the stable period of synoptic pattern, the cyclone tracks after explosive development are also stable, during the adjustment period of synoptic pattern, the cyclone tracks change with the change of long wave system over 500 hPa, while the wavelength decrease