Abstract Temporal and spatial variations in the structure of the lower atmosphere off Oregon's central coast are studied. The response of the wind and thermal fields to a synoptic-scale realignment aloft that causes a rapid shift from surface southerly to northerly winds is detailed. The effects and importance of the infrequent southerlies on the marine inversion, sea breezes and upwelling is also investigated. A vast array of meteorological and oceanographic observations were measured by aircraft, land stations, buoys and ships during the first Coastal Upwelling Experiment I (CUE-I). The winds, air and water temperature, and currents from the surface ocean layer to 1.5 km are compared during 16–29 August 1972. The period of southerly surface winds created a warm moist lower atmosphere, weak sea breezes, and brought about a cessation to previous upwelling. In contrast, northerlies and ridging aloft produced a distinct marine inversion, strong sea breezes, and an upwelling event. The marked changes reveal ...