On December 16, 2019, short-duration heavy rainfall leads to flashfloods occurred in Khuzestan province, causing many problems for the people in Ahvaz and Abadan. In this study, return period of precipitation and atmospheric pressure patterns leading to this flooded was studied.
The data recorded at Abadan station in southwest of Iran is obtained from Iranian Meteorological Organization. To select the suitable distribution, the Anderson-Darling test is used. Based on this test, the two-parameter lognormal distribution is distinguished as the best one to be fitted on the recorded precipitation of the Abadan station. The statistical distribution characteristics are extracted by using the statistical Minitab software. In this paper the two-parameter lognormal distribution function is used to calculate the return period of the maximum daily precipitation in Abadan station.
Statistical results showed that the extensive rainfall with a high return period and lack of necessary infrastructures to collect surface water can be the major causes of flooding in Abadan.
Synoptic analyzes showed that crossing pressure patterns, which are associated with atmospheric fronts, over Southwest of Iran can provide conditions for extreme weather events spatially gust fronts and sever convective rainfall in the region. High relative humidity and intense vertical velocity in the lower and middle levels of the troposphere are the main factors affecting heavy convective rainfall in the region; the former was due to the humid and warm southerlies winds at the surface and the latter was due to the cyclonic relative vorticity advection in the middle level troposphere.