عنوان مقاله [English]
In order to investigate synoptic-dynamic situations which results in thunder storms in South Western parts of the country, data were exploited from 16 synoptic stations in South West of Iran during a 10 year statistical period (1996-2005). Fitting the precipitation data, six types of severe storms were identified. Exploring the exploited systems, two general patterns were identified for thunder storms with severe precipitation. The first pattern follows integrated systems pattern, so a ridge from North West Africa to Scandinavia causes cold weather falling on the Mediterranean Sea and deepens the Mediterranean trough, which in turn strengthen the East Mediterranean low altitude center. Continuous cold weather falling on this cyclone center increase pressure gradient in east Mediterranean area and makes penetration of 500 hecto Pascal trough toward middle Red Sea possible. Increased temperature gradient over North Africa and the Red Sea strengthen Sudanese system and while moving toward North of this system integrates with low pressure Mediterranean system and results in unsustainability in West and South West Iran. The Second pattern is a low pressure Sudanese one. Low pressure Scandinavian system result in cold weather of pole neighboring latitudes falling into lower latitudes. Azore anticyclone which is formed over North Africa transfers cold weather to North Africa, aggravates unsustainability, strengthen Sudanese system and creates a weather front. Thunder storms require access to hot and humid weather which is injected into the area due to the proximity of Southern seas.