As the days shorten, temperatures cool and we head into an autumnal weather pattern it is typical for the forecast to include comments about High pressure moving inland toward the Great Basin. When this happens Northerly interior winds develop that turn toward the NE or ENE as the High moves inland. Right on cue that is what we saw this week, and that generally means weaker beach winds as the offshore winds and cooler temperatures battle sea breeze activity at the beaches. But this past event was not typical. Instead of weaker winds the Ventura to Leo Carillo stretch of coastline saw winds topping 30 kts.
Some of the basic ingredients for strong sea breeze activity were not in play that day. Typically we need warm air in the local valleys. That was certainly not the case as a cold front had just dropped cooler air over the LA Basin which kept the local valleys in the 70s.
Also usually needed is a strong onshore gradient to produce winds at these levels. The gradients will help to pull the ocean winds over the coastline and accelerate them toward inland Low pressure. Instead, we had the opposite pattern. The pressure gradient reading from the LA Basin to Daggett started at a -1.7mb in the morning and didn’t become positive (onshore) until later and even then it was only slightly positive (onshore).
But what we did have was a Northerly component to the gradients. So there were strong NNW/NW winds offshore at the buoys and also strong NNE interior winds. The unique topography of Southern California converges these winds just offshore from the Santa Barbara coast. This becomes the convergence spot of a lot of energy. Many times this energy stays offshore and our forecast will discuss the fact that there will be strong winds offshore that don’t reach the sensor. But when we have just enough strength from the NW coastal flow these winds will be pushed back over the coast, bringing a standout afternoon. It is a tough forecast call, as only a small difference will produce significantly stronger winds. But when it all comes together we can have an epic wind afternoon.