Spatial and temporal distribution of storms and their activities over the Bay of Bengal

By statistically analyzing the storm data from the Joint Typhoon Warning Center (JTWC) over the Bengal Bay during the period 1945-2006, it is found that the yearly averaged tropical cyclone (TC) number over the Bay of Bengal is 8.12, which takes place in any month of the whole year; February and March have the fewest TC numbers. The TC numbers begin to increase starting in April and arrive at a peak in October. Differing from TC over the Bay of Bengal, the tropical storms (TS) over the Bay of Bengal has two peak periods, appear in May and in October or November, respectively. With regard to TS intensity, the super severe storm of H4 criterion appeared only one time during the period 1971-1986, but appeared eight times during the period 1987-2006. The monthly change of the original position, the averaged maintaining time, and the longest maintaining time of TS also have two peak values: They appear in April or May and in October or November, respectively. The peak value of the original position in October or November is bigger than that in April or May. The peak value of the average maintaining time and the longest maintaining time of the TS in April or May is bigger than that in October or November. TC landfall path is mostly moving toward northwest or west and accounts for 56.7 percent. The landfall path of the TS differs from that of TC in some respects. The main difference is that the numbers of the northwestern path and un-landfall of TS are less than those for TC, and the numbers of the western path and northeastern path of TS are greater than for TC. Because of the landfall TS in the north-east path has a peak, it and the beginning of the rainy season in Yunnan Province are closely related; it is on Yunnan Province's early summer precipitation that they have a great impact.