This study focus on the interaction between the coastal flow field and the evolution of the coastal stratocumulus clouds. The data collected during an experiment in the summer of 1999 near the central California shoreline with the CIRPAS/NPS Twin Otter research aircraft showed that the low level coastal wind jet close to the boundary layer top some tens of kilometers offshore occurs quite frequently. In some occasions the wind jet was quite intense and affected significantly the structure of the stratocumulus layer. On the 6th of July 1999 a strong wind jet (peak wind speed of 20ms^-1) was observed at the height of 500m just below the boundary layer height about 75km offshore. This wind jet seemed to be connected with a zone of cloud breakup parallel to the shore starting from Cape Mendocino to the north. The mean fields and turbulence vertical structure obtained using data from flight legs through the wind jet area at different times showed that the mechanisms of this local cloud breakup were a negative surface buoyancy flux connected with a cold pool of sea surface temperature and the enhanced entrainment at cloud top due to wind shear from the wind jet. The north origin of the cloud free zone suggested also that topographical features probably intensify this wind jet at some places near the coast and, thus, create a cloud free zone.