Synoptic regimes associated with the eastern Mediterranean wet season cyclone tracks

Abstract

The main synoptic patterns associated with the wet season (October–May) eastern Mediterranean cyclones have been analyzed and described using NCEP/NCAR reanalysis datasets for the period 1958–2013. The cyclone tracks detected in the eastern Mediterranean are classified into two types based on their positions: the local tracks and the long tracks. The local tracks are either stationary or short tracks. The long tracks distinguished into eleven very closed and highly correlated clusters, which are presented into three regimes namely the northern, the southern and the eastern border Mediterranean regimes. Among the 940 (44.78% of a total of 2099) long tracks, the northern, southern, and eastern border regime contributes respectively about 53.62%, 41.81% and 5% of the long tracks. In addition, the distribution of the long tracks reveals that a larger proportion of the cyclones are generated at the northern coast during November and spring months, while few cyclones are developed over the eastern Mediterranean border in warm months (April and May). Further, their synoptic features show that the regimes are associated with the extension of Azores high, specifically for each regime, the cyclogenesis areas of its clusters are controlled by the intersection of low level (850hPa) trough and the position of the upper level (250hPa) maximum wind. Furthermore, the orientations of clusters are controlled by the extension of Siberian high and the shape of cyclonic trough at 850hPa. In addition, the synoptic study shows that most of the southern cyclones generated externally by African and Red Sea troughs, while most of the northern and eastern border cyclones are generated internally.