Upper winds and mesoscale easterly flows in the Latrobe Valley

Upper air data for heights up to 3 km in the Latrobe Valley area have been examined. The prevailing winds are westerly at all levels due in part to the topography of the area. A three-level flow structure is indicated on about one morning in four with slope or drainage flows, generally shallow, but occasionally as deep as 100 m, an intermediate flow (low-level easterly) above these from about 100 m to as much as 700 m, and the synoptic flow becoming predominant above this level. Ambient Froude Numbers on these occasions are typically about 1. The intermediate flow is from the east with upper-level winds from the northwest and appears to be due to a mesoscale interaction of the synoptic pressure gradient and the local topography producing a diversion of the low-level flow towards low pressure.