The primary objective of this project is to increase basic understanding of several important mesoscale features of the lower troposphere of western North America that are produced by the complex terrain of the region. The greater emphasis will be given to low-level phenomena that are trapped by the coastal topography such as the coastal southerlies and along shore surges that are observed within a few hundred kilometers of the coast from Baja, California to British Columbia. Closely connected with the coastal southerly currents re mesoscale coastal eddies, such as those observed off California (e.g. the Catalina eddy). A second project will be to examine the diurnal and semi diurnal surface pressure variations over the United States both to create a valuable diagnostic tool and to better understand the mesoscale variations and physical mechanisms of diurnal pressure change. The final component of the proposed research will be the examination of the mesoscale troughing. Such troughing is associated with the Puget Sound convergence zone and contributed to the destruction of the Hood Canal Bridge in 1979.