Analysis of Snow Storm (Alexa) synoptic conditions which affected the Jordan during the period 11-14 December 2013

Abstract

The study aims at investigating the synoptic conditions associated with Alexa storm that affected Jordan between December 11 and 14th, 2013. To do this, the researcher analyzed weather maps (1000, 500, and 300 hPa) and tephigram diagrams to identify changes in weather elements (e.g. relative humidity, temperature, air pressure, dew point , wind speed and direction) during the same period of December. The weather records for five weather stations (Irbid, Ras Muneef, Sweileh, Al-Mafraq, Al-Shoubak, and Ma’an) were also studied. The research showed a significant relationship between the severity of Alexa storm and existence of a very low pressure cell above Jordan which accompanied with arctic air mass. In the upper atmospheric layers ( 300 and 500 haP), results showed existence of northeastern to southwestern upper trough which attracted cold air from eastern Europe to the eastern region of the Mediterranean. This cold air flow increased the severity of the low pressure cell and resulted in maximizing rainfall rates. For example, rainfall amounts in Sweileh, Ras Muneef, Irbid, Shoubak, and AL-Mafraq were: 164.4 mm, 106.3 mm, 89.3 mm, 52.6 mm, and 19.4 mm, respectively. The storm Alexa also resulted in accumulated snow that reached 136 cm in depth in Ras Muneef and 180 cm in depth in Sweileh. The storm Alexa caused dramatic damages to infrastructure in Jordan and the considerable amount of snowfall paralyzed life in entire Jordan for days.