Upper air trough axis orientation and the spatial distribution of rainfall over Israel

Since Israel is located far from large oceans, availability of moisture may be a limiting factor in producing rainfall by synoptic‐scale disturbances. Thus, moisture evaporating from the nearby Mediterranean Sea may become an important factor in producing precipitation in the region. A simple scheme has been designed to test the hypothesis that rainfall over Israel is largely affected by the trajectories of air prior to the rain event. The relationship between air trajectories before a rain event and the intensity and spatial distribution of rain over Israel has been examined. We discovered that a large percentage of rain events is associated with maritime air trajectories. Since the Israeli coastline bends sharply towards the west near latitude 31 °N this means that the orientation of synoptic disturbances responsible for precipitation to the north of 31°N and to the south of this latitude are markedly different: troughs in the lower troposphere that are oriented from north‐east to south‐west produce relatively more rain over the south of the country, while troughs that are tilted from north‐west to south‐east or from north to south produce relatively more rainfall over north and central Israel.