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In order to analyse the synoptic conditions of the rainstorm period of 12 to 17 july 1999 in Iran, the daily 00 GMT weather maps of the surface , 850 , 700 and 500 hpa levels were analysed. On the weather maps the location and movement of the weather systems such as cyclones, anticyclones , fronts and westerly waves were identified.
The results showed that the expansion of monsoon low from the south and southeast and migratory anticyclones from the north caused the rains . At the upper levels, the westerly waves played very important role. High pressure system has advected the cold air in to country and the monsoon low pressure system brought the moisture from the Indian ocean. Westerly trough moved over I5ran and was blocked by the subtropical high pressure.
Key words: synoptic, rains , july , Iran