Investigation of the synoptic patterns of important fronts in rain and flood formation in west of Guilan province

The storm events are one of the most devastating natural disasters that have imposed many damages to human communities during the course of history. The various air masses cover Guilan Province and each one of them impose seasonal and sever rainfalls on the province. As a result, the water level rises and the occurrence of the floods is indispensable. According to the statistics and documents during the recent decades, huge floods have been occurred in the province, leading to death and economical damages. The synoptic patterns of atmospheric conditions in the region control these types of phenomena. The synoptic maps, at different levels of the atmosphere, can be monitored. Many of the earth's surface phenomena, such as floods, droughts, frost, etc., can be identified through the synoptic maps. One of them is the amount of rainfall available to each region, which can be determined by studying the synoptic maps. Moreover, One of the most important factors leading to occurrence of flood is weather phenomena, such as intense cloudbursts and rainfalls. Climate study and identification of weather phenomena, especially the cloudbursts have an important role in forecasting the floods and making flood warning plans. Therefore, this research has been conducted in order to analysis the the cloudbursts leading to flood in west of Guilan Province. For this purpose, statistics of floods and local cloudbursts related to each flood in west region of Guilan were identified and drawn out since 2001 to 2011. Accordingly, during this period 13 floods and local cloudbursts were identified. In the next stage, serological isobar plans for the sea level of 1000 m and geopotential of 500 Hectopascal for pre–rainfall days and rainfall day were obtained from NOAA and each of them was observed using isometropia analysis method consistently analyzed using the GrADS software for mapping required at the ground level. The results showed that there were 7 weather patterns effective in the formation of these rain storms. Among the seven models of high-pressure, the Scandinavian and Mediterranean systems were the most affecting systems on the flooding and flood events in the western rivers. In addition, the rain storms have been caused by the presence of at least one high-pressure system.