Surface Pressure Perturbations Produced by an Isolated Mesoscale Topographic Barrier. Part II: Influence on Regional Circulations

Abstract

This paper describes the detailed pressure and surface wind evolution associated with several important mesoscale phenomena in the region surrounding the Olympic Mountains of Washington state. The data used in this study were collected during the Olympex Experiment, during which eleven high-accuracy microbarographs were placed around the Olympics. The diurnal sea level pressure and surface wind variations of western Washington are described: lower pressure is observed over elevated terrain during the day with the opposite configuration at night. Next, this study documents the closed mesoscale lee lows that form in the lee of the Olympics during strong south-southwesterly synoptic flow regimes. Such lee lows create intense sea level pressure gradients and large ageostrophic accelerations along the eastern slopes of the Olympics. Another important feature examined in this paper is the Puget Sound Convergence Zone; it is shown that troughing in the lee of the Olympics plays an important role in determining the wind field associated with this event. Finally, the mesoscale sea level pressure and surface wind patterns associated with varying 850 mb wind speed and direction are examined.