Synoptic Survey of Floods Caused by Heavy Rainfall of 4 February 2006 in the Lorestan Basin

Synoptic patterns is one of the important parameters in climate studies and atmospheric behavior of the system causing flooding in any area. This study examined the Synoptic conditions in the February 4, 2006 flood basin of Lorestan. The aim of this study was to assess the flood Synoptic February 4, 2006 in the province of Lorestan Basin This rainfall recorded rainfall over 70mm in excess of 15 rain gauge and synoptic stations and cause flooding and damage in southern of province. Rainfall data from 64 stations in the study area were used up. Rainfall data were used from 64 stations in this study. The digital files maps of sea level pressure, geopotential height of level 500mb, blowing moisture level of 700mb and U-wind of level of 200mb were provided of NCEP data center.The results show that three factors exist floods damage; low surface pressure in this area, located west wind advection on ground low pressure and adaptation of left output shaft of subtropical Jet-Stream on advection of westerly winds are the main cause of the flood in this basin. Overlaying of right entrance of Polar Front Jet-Stream on advection of westerly winds has been very effective in enhancing the instability