Steve,
It has been far too long for me to remember what time of year Dana was hanging out in S. California. A quick squint at the chart and you'll see that in S. California the coast runs North/South down near Mexico, but turns in a big sweet and runs almost East/West from Santa Barbara west to Pt. Conception. This makes the entire area south of Pt. Conception into a sheltered area of calm winds and flat seas (relatively) during the 9 months of the year that there aren't many storms of any kind (other than hot offshore Santa Ana winds). The existence of a chain of 8 large islands, actually a submerged mountain range, that run from Richardson's Rock which is out West near Pt. Conception, all the way down to San Diego makes the entire S. California basis an area that the Square Rigger Captains referred to as the Catalina Harbor.
The problem with this "Catalina Harbor" is that in the winter when the storms arrive they can be preceded by extremely strong southerly winds, which you obviously know as we're in the N. Hemisphere. Those southerlies often reach 30-40 knots with gusts above that. Indeed, we just had a series of them blow through with winds in this range and seas reaching 15-20 feet on the S. Calif. beaches. In these conditions, the entire Catalina Harbor becomes a massive lee shore and unless on shifts from previously safe harbors on the mainland to the N. side of one of the Channel Islands, it can be a death trap for ships. Many of us start seamanship talks around here with one comment that wakes up the audience: All of the California Coastline is a lee shore. In the summer nearly every mile of it is a lee shore to the NW winds in the winter the same happens with the SW winds in gales.
To make matters worse.... along the large bays of Dana's time (which would include San Diego, Los Angeles, Santa Barbara, and Monterey) there is great sand and mud bottom to be found all along the shore. Within these Bays the coast shoals relatively gently, almost like the E. Coast which square rigged ship sailors were accustomed to. Everywhere else, the shore is extremely steep to and rocky with foul anchorage except in small holes which were inappropriate for boats/ships that can't sail to weather when then need to. The sand/mud bottom in these big Bays exists because the 9 months of prevailing NW winds and strong California Current running down the coast pushes all the silt, sand, and mud down the coast until it settles in one of them. The typically windward side of the Islands that make up the Catalina Harbor (Catalina, San Clemente, Anacapa, Santa Cruz, Santa Rosa, and San Miguel, going from SE to NW) is scrubbed clean of sand/mud and and typically quite steep to; meaning that depths about 100 yards off shore are well over 200 to 250 feet and rocky. Thus, when the winter Southerly winds come on the front of the gales, the natural place to anchor, in the lee of these islands, is quite difficult for a ship of the 1800s.
Finally, during the fall S. California receives its famous Santa Ana winds, which howl down the canyons and blow out to see at speeds of up to 70 and 80 knots. While these are off-shore winds when one is anchored near the mainland, and the waves don't have a chance to build up, with the windage of a Brig or Full Rigged Ship and old anchors with rope rode, it might be hard to hold even in sand. They arrive quickly, without warning, and as recently as the 1950s washed dozens of boats ashore in the normally protected harbor of Avalon on Catalina Island. Ships of the 1800s were probably ill equipped to deal with hurricane force winds with 10 minutes notice while at anchor.
In this news media pic you can see the configuration of the islands, where the Santa Ana winds come from, and why the Catalina Harbor could be so dangerous.

Here's a picture of Avalon Harbor after a Santa Ana, this was a mild event. In prior years all the buildings along the waterfront have been destroyed in a matter of an hour or two.
