Synoptic analysis of extreme rainfall over 20 mm precipitation for flood warning in Sistan and Baluchestan

Precipitation is one of the most important climatic phenomena. Understanding the spatial and time distribution of precipitation has a significant role in the planning and management of water resources and flood risks. In this study, daily precipitation data from synoptic, climatology and rain-gauge stations of Sistan and Baluchestan during 25 year period (1990 – 2014) are collected. The numbers of 24 hours precipitation with extreme rainfall of 20 millimeters or more at stations evaluated and by using of Statistical software are investigated. Then zoning map for extreme rainfall of 20 mm by GIS was obtained. Assessing of zoning map showed that the most effect of extreme rainfall has happened in coastal areas and southern province. Time distribution of extreme rainfall showed that 80 percent of extreme rainfalls have happened in cold seasons (autumn and winter). Hence, Synoptic conditions of western systems are assessed. Applying synoptic analysis of different maps such as humidity levels of 500 and 700 H.P., sea level pressure, 500 H.P. pressure and convective available potential energy maps, showed that enriching of precipitation systems by the Persian Gulf and Oman Sea in cold seasons are caused extreme rainfall of 20 mm in Sistan and Baluchestan Province.