As the days shorten and temperatures get cooler and we enter a fall weather pattern, weather forecasts often include comments about high pressure moving inland into the Great Basin. When this happens, northerly internal winds develop and turn to the northeast or east-easterly as high pressure moves inland. That's exactly what we're seeing this week, which typically means less beach winds as offshore winds and cooler temperatures battle sea breeze activity on the beaches. But this past incident is not typical. The winds along the coastline from Ventura to Leo Carillo did not weaken, with wind speeds reaching 30 knots.
Some of the basic elements of strong sea breeze activity that day were not working. Often we need warm air from local valleys. That's not the case, as a cold front just dropped cold air over the Los Angeles Basin, keeping local valley temperatures in the 70s.
Strong onshore gradients are also typically required to generate these levels of wind. The gradient will help pull sea breezes across the coastline and accelerate them toward low pressure inland. Instead, we have the opposite pattern. Pressure gradient readings from the Los Angeles Basin to Dagit started the morning at -1.7mb and did not become positive (onshore) until later, and even then the pressure gradient was only slightly positive (onshore).
But we do get the north component of the gradient. Therefore, there are strong NNW/NW winds offshore at the buoy, as well as strong NNE internal winds. Southern California's unique topography funnels these winds offshore along the Santa Barbara coast. This becomes a gathering point for a lot of energy. A lot of the time, this energy stays offshore, and our forecasts will discuss the fact that there will be strong winds offshore that won't reach the sensors. But when we get enough strength from the northwest coastal flow, those winds will be pushed back toward the coast, making for an outstanding afternoon. This is a tough forecast because just a small difference can produce significantly stronger winds. But when it all comes together we can have an epic windy afternoon.
