Analysis of Circulation Field During the Abnormal Frequency of the Tropical Cyclone Affecting East China in the Flood Season

Before forecasting the frequency of the tropical cyclones affecting East China in the flood season by using statistical interpretation forecasting method, a series of earlier stage researches are made. It’s found that: (1) Abnormal frequency variation of the tropical cyclone affecting East China is caused by the adjustment of mean monthly circulation of the Northern Hemisphere in flood season; (2) The long wave reflecting the characteristics of mean monthly circulation has a good relation to the abnormal frequency variation, especially in abnormal years the weather system and the correlation area are stable; (3) Using the correlation analysis the statistical forecast equation for the frequency variation of the tropical cyclone is set up. Based on the correct short-range numerical forecast for climatic situation the accuracy is about 70% using statistical interpretation forecast method, and if the abnormal variation of mean monthly circulation could be predicted, the trend of abnormal frequency variation could be predicted.