Synoptic Analysis of Pervasive Hail Precipitation in the West of Iran

Pervasive and severe hail precipitation has an effective and main rule on damaging to agriculture products in different earth zone. in order to study the dynamic and synoptically conditions of hail phenomenon in west of the country, used daily of hail precipitation of 30 synoptically stations of Kermanshah, Hamedan‚ Lorestan and Kurdestan states in a 10 year statistical period (2000-2010). 2 sample of pervasive hail precipitation which had more intensity than the other, recognized and chosen. The results showed that in the light of boarding period, 9 Am to 15 pm and between the months of the year, April and May had maximum values. Synoptic stations of Marivan, Baneh, and Bijar had maximum hail occurrence. Study of the atmospheric patterns showed, pervasive hail precipitation in the zone is the result of expansion of low pressure system which is located on the Red Sea and Sudan. In the day of hail precipitation the west of the Iran, settled in front of the trough and Arabian sea anticyclone system caused transferring of the warm and humid weather with northern-southern direction weather to the zone and while the strengthened Sudan low pressure system made suitable conditions for instability creation and hail precipitation. Studying omega maps, showed the convergence of edge level of 1000 hpa and strong divergence level of 700 and 850 Hpa. So that strong upwards flows ascended the warm and humid weather and prepared the ground for creating the intense instability.