Statistical analysis and synoptic spatial and temporal patterns of precipitation Chance of Thunderstorm (Case study: Zanjan)

Thunderstorm a weather phenomenon that due accompanied by thunder, lightning, wind and rain, intense search in addition to the positive impact that they can cause a lot of damage in different parts of the world. Due to the variety of weather conditions, the occurrence of this phenomenon is observed in different regions. North West of the province, especially not immune from this phenomenon. To study the phenomenon in terms of statistical and synoptic data daily thunderstorms Thunder in the province of Zanjan synoptic stations in a 16-year period (2009-1994) were used. The results of this study showed that the average frequency of precipitation Thunder northern parts of eastern, central and south of the province with the highest coefficient of variation are also based on these areas. The eastern and western parts of the province had the lowest average and the lowest coefficient of variation Thunder also have. With this interpretation in the months of March and April are the months of heat transfer (Spring), are due to the warming of the Earth's surface and lower layers of the atmosphere (the rise of the sun during the day and close to the vertical) and high atmospheric moisture, instability and flow convection intensified under the right conditions, convective clouds grow and so will thunderstorms. Cold transitional season (autumn) also Frat cool air from higher latitudes to the southern temperate zones than the underlying causes of instability are required. However, due to the lower humidity in the fall than in the spring, the intensity of thunderstorms in the spring and autumn much less. Analysis results show weather maps at different levels-the most important synoptic systems represent the region on the tab of Mediterranean and the Black Sea and the Mediterranean and Red Sudanese have strengthened the role of the North West the country and the province. West winds around the landing position with the main cause of instability in the region Low pressure cut off by severe thunderstorms in the province.