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Description
This study focused on meteorological events in the Santa Barbara Channel and Southern California Bight occurring from September 1995 through August 1997. Based on observations from automated meteorological stations throughout the Southern California Bight, three radar profilers, National Weather Service analyses, and visible satellite imagery, analyses of the data are presented to illuminate three distinctive events: strong northwest wind events, lee heating wind events, and coastal eddies. Variables were plotted and statistics developed to determine the occurrence, strength, and aerial extent of events, focusing on the Santa Barbara Channel. Strong northwest wind events are defined, based upon buoy winds in the western mouth of the Santa Barbara Channel, as northwest winds exceeding 12.9 m/s in the summer and 11.3 m/s in the winter, for six or more consecutive hours. Strong northwest wind events are associated with trough passage, sometimes short waves, at 700 millibars. During winter, events occurred immediately after strong frontal passage through the Southern California Bight at the surface, or after frontal passage east of the bight accompanied with high pressure offshore. During summer, events were associated with persistent high pressure offshore and a thermal low in the Desert Southwest, with event speeds reached when there was trough passage over the Santa Barbara Channel at 700 millibars. Lee heating wind events are defined as northerly downslope winds of around 10 m/s or more in the lee of the Santa Ynez Mountains, with temperatures exceeding the mean maximum in the Santa Barbara area. Lee heating wind events generally lasted a few hours and occurred mainly between 2100 and 0000 UTC. The maximum temperature for an event was 37.9°C. Lee heating winds extend offshore, mainly, and sometimes exclusively from Gaviota West, where they meet the marine layer and deflect to the east. Occasionally these winds reached HONDO Platform, but never mid channel Buoys 54 or 53. Although National Weather Service analyses were consistent with northerly offshore flow in the Santa Barbara area, lee heating wind events occurred over a very limited aerial extent. These events showed no systematic correlation to synoptic scale pressure gradients. The temperature inversion structure and wind structure at the Goleta radar profiler during lee heating wind events were not consistent with mountain wave dynamics. Coastal eddies in the Southern California Bight cause winds in the Santa Barbara Channel to be from the south or southeast. Often these wind reversals bring low level stratus, cool temperatures, and southerly flow to the entire Southern California Bight. Coastal eddies were identified from sustained southerly winds at San Diego, and were confirmed by satellite imagery. They are associated with synoptic scale troughs moving into the Southern California Bight from the north, appearing most clearly in 850 millibar analyses. Wind, pressure, and temperature fields in the Southern California Bight and the Santa Barbara Channel are inconsistent with a cause for eddy development resulting from a mesoscale trough in the lee of the Santa Ynez Mountains.
