A Synoptic Analysis of January 6, 2008 Heavy Precipitation in the Southeast of Iran

IntroductionPrecipitation is a variable and irregular over most part of Iran. Therefore it is a very important factor in planning procedures throughout the country. The spatial variation of the annual precipitation varies from 1800 millimeters in Anzali to less than 50 millimeters in the arid and semi-arid deserts of the southeast. Its temporal variability is much higher than the spatial variations. More than 90 percent of the daily rainfall comes in low and moderate intensities. But sometimes very intensive and torrential rains occur, especially in the arid climate of the country. These extreme rainfalls are characteristics of the dry parts of the country such as the southern coastal areas. Humidity of the Persian Gulf and Oman Sea and the deep and intensive westerly cause torrential rains during the cold seasons. Sometimes the rainfall hit more than 80 percent of the annual precipitation. Therefore the very important role of it in the management and development of the region is not deniable. The results and understanding of these patterns will help the authorities and planning managers. The most important factor resulting the torrential rainfalls is the pressure patterns of the westerly. This paper investigates concepts of the westerly pressure systems in very intensive daily rainfalls of the southeast of Iran. Data and Methods In order to understand the pressure patterns of these heavy rains, the daily rainfall data of 25 weather stations of the southeast region of Iran were obtained from I.R of Iran Meteorological Organization during the 1997-2007 period. The heaviest daily rainfall is a day having at least 100 millimeters rainfall in one third of the stations under investigation, for sure. In the analysis of the cold season, January 6, 2008 was selected as