There are loads of areas in the "Big Bay" that focus and shape the local wind... the best known of these is right at Pt Loma between the south end of Zuniga jetty and Ballast point. The wind almost always intensifies there, except when it comes out of the south... which is rare.

There are some of these same "hot spots" in the Shelter Island approach, just past the seal pens. If there are Carriers in place at their berths, they too act to focus the wind along the Coronado edge of the bay at that corner opposite of the end of Harbor Island... between the carriers, the wind jets out. There is a wind focus area at the entrance to Harbor Island at the west side of the entrance.

Just past the bridge, and the entrance to Glorietta bay, you can bet on a nice fresh breeze off the ocean, again focused by the Coronado condos and the bridge itself.

Local racers use this knowledge whenever possible.

You may be in one of those wind focus zones... these are miniature versions of what happens on the Columbia River Gorge. (very miniature versions)

As for the airport... most likely their anemometer is much higher than yours. Heck, it may even be on a building just off the airport property... I honestly don't know. I do know that both SAN and Montgomery show more averaged wind speeds than peak. There are anemometers on local schools that show peak winds better. San Diego rarely gets 30kts of wind.

The URL below is from the the weather underground station of SDYC... you can see there is quite a difference between the peaks and the average, and how rarely we do in fact get 30kts.

As far as accuracy... I'd watch the ripples on the water... they rarely lie. I don't have any wind instruments... so I have no other choice.