Analyzing the Synoptic Systems in the Northern Provinces of Iran during Heavy Snow Events (A Case Study Is January 31 to February 3, 2014)

Snow depth data from the Iranian Meteorological Organization was used for the period of January 31 to February 3 2014 in order to study the precipitation of heavy snow in the northern parts of Iran. 1.5 to 2 meters, in some parts more than 3 meters, of snow in 4 days were reported. To analyze the circulation patterns causing this precipitation, air temperature data, Geopotential height, sea level pressure, and sea surface temperature, vertical velocity (Omega), and the orientation and zonal components of the wind were taken from the website of National Center for Environmental Prediction and National Center for Atmospheric Research (NCEP / NCAR) with a resolution of 2.5 by 2.5 degree and the synoptic maps were prepared. The results showed that in the event of heavy snow, the Eastward surface pressure in East Europe and the establishment of a barrier system at 500 hPa in the region along with a very deep trough on the Caspian Sea with NE-SW Brewer caused positive vorticity and the resulting instability initiated the snow fall. On the other hand, the sea surface temperature anomalies in the southern part has exceeded 2 ° Centigrade and caused the transfer of moisture to the entering cold air mass as well as the extreme temperature gradient which triggered the formation of a Front in the Caspian area. The polar vortex in January and February were therefore located exactly on the region, escalating the condition.