Synoptic analysis of heavy rainfall in November 21, 2011 in Kohkilooyehand BoyerAhmad (Likak)

Heavy rainfall and its direct and indirect effects on human’s lives and activities not onlyjustify the attention to the peripheral phenomenon but also provide the way to predict theirfuture occurrence.In thisstudy, after selectin gcriteria for Iran’s heavy rainfallin theSouthWest, theperipheralto circulation approach was used and the synoptic conditions at thetime of the event(21November2011) was evaluated. Results show that the progression ofSudan low pressure from the South and the European high pressure from the North and thecollision of the setwohot and coldsystems have made the mass in West and SouthWest of thecountry. In addition,in the middle level of atmosphere deepening of the Mediterraneanlanding area and its East- toward movement on the same day has located the study area in theEast Region of the landing are a which is the positive volubility area and the created spin hasmoved to the East. Therefore, Due to the severe the rmalinstability and gradient this led torising air in the region.Highhumidity has also contributed to instability and has providedconditions for heavy rainfallin the region more than before Also, one of the other factorsaffecting the heavy rainfallin the study area is that he subtropical river windspeed core haslocated on the Red Sea andin the north of Arabia.