|Image from the video at 1:12 PM Feb. 12|
The temperature and dew point at Skunk Bay (see graphic) and other nearby sites (e.g., Wahl Rd on Whidbey Is, also shown) were close but not at saturation (the dew point was a few degrees less than the temperature).
air was forced up quickly along that share.. As the air was forced to rise, it cooled (air moving from higher pressure to lower pressure expands and cools). The temperature fell to the dew point and the air became saturated, producing a cloud. As shown in the picture above, and the video below, the cloud was not only maintained over the land, but streamed downwind of the island.
How much will air cool moving up a slope? If we assume that the air rose 100 meters (328 ft) and assume the dry adiabatic lapse rate (9.8 C per km, the rate that unsaturated air parcels cool when they are forced to rise), we get a decrease of .98C or 1.8F, which was enough to bring the temperature down to the dew point.
Greg Johnson produced a wonderful slow-motion video of the event; click on the image to view it yourself.
If you want real visual treat, check out his melding of TWO cams into one wide image--it doesn't get much better than that! (click on image below):