Statistical analysis and prediction of occurrence probability of violentStorms using partial - series analysis method(Case study: sistan area)

About 90 percent of natural calamities that occur in the world are related to climatic factors and among them storms after flood include 30 percent of these calamities. This phenomenon is one of the most perilous natural calamities that has a climatic origin and imposes irreparable financial and physical losses every year. Sistan which is one of the stormiest areas is located at the south east of Iran and the north of Sistan & Baluchestan Province. Anemometry date of synoptic from Sistan of zabol were used to analyze the storms of the velocity of 24 m/s and more statistically and also to predict the occurrence probability of violent storms by partial series analysis method during a 30 years period (1359-1388) and data accuracy and equality were identified by run test. Conclusion was obtained from statistical analysis showed that 162 stormy days of mentioned velocity have been observed in Sistan areas during the studied period. The years 1362 with 64 stormy days were with highest number of observations. Among storms, 3 cases have been observed of the velocity of 40 m/h (144 km/h) that suggest the violent of storms in sistan. Among seasons and months, summer and winter respectively have got the maximum and winter and month Day have got the minimum stormy days. Plotting the annual and seasonal storm-rose using WR plot software shoed direction of predominant storms of area was north of north-west (NNW), north (N) and north-west (NW). The prediction carry out by using partial series analysis method and different return periods suggest the occurrence probability of storms of the velocity of 42 m/s (151 km/h) and less in Sistan. Therefore these storms must be considered in environmental planning of the area and structure safety to minimize the losses if they occur.