As it strengthens, it buffers the Bay Area from storm systems. Clear skies prevail, allowing the sun's warm rays to dry the soggy landscape. The Central Valley heats up. The resulting rising air mass is substantial enough to create an area of low-pressure, the Central Valley Low. On its way it sweeps over us.
Gusts are especially strong on clear, sunny days.
A walk across the Golden Gate Bridge against these winds is testimony to the force of this gradient. The winds also begin the local food chain. Their force literally pushes off the top layer of ocean water. This warm layer of water is replaced by cooler water pulled from the depths to the surface, in a process called upwelling. Phytoplankton, tiny oceanic plants, which are dormant in the cold, dark water, bloom in contact with the sun.