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Abstract:
Southeastern district of Iran is arid and semiarid. Inconsiderable, rainfalls in this area are classifiable under influence three distinct synoptic systems. The first systems are those cyclones which along with western winds of moderate areas penetrate into district farm west, and cause 57.5 percent of the precipitation. These rainfalls are tiny but continuous and occur in winter season. The second systems are made by short waves of western winds as their trough grows deeper. They bring humidity into the region through southern seas such as Persian Gulf, Oman Sea and Red Sea. They cause 33.68 percent of the region rainfalls. The third systems are those low pressure systems that called Indian Monsoon and through wide circle, bring the Indian Ocean moisture into the region and cause .82 percent of its rainfall. The second and cause little 8 precipitations although most of the time they transfer the humidity of ocean and seas into the region .Analysis of climatology are suggested in order to fertilize these kind systems.

Key words: Synoptic systems, Monsoon low, Short waves, Sudan pressure systems, Pakistan low pressure systems, western winds