Sudan low system is the one of important element of general circulation in north Africa that it has been forming west of Itupii and north of Sudan. with deepening of north Africa trouph in cold period of year,this system change to thrmodynamicaly state and by eastward movement of this trouph, the sudan low spread into the Iran and precipitation is begin.The synoptic pattern of siberian high, North Africa and Arabian peninsula anticyclone,North Africa trouph and sudan low in low and middle level make four principle patterns for deepance and development of sudan low over Iran.
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