Source: Weaver, Robert L., 1962: Meteorology of hydrologically critical storms in California. Hydrometeorological Report No. 37, US Army Corps of Engineers and US Weather Bureau, 207pp.
This shows the tracks of the major surface low pressure areas from 13 February to 18 February 2004. The red track was associated with a strong occluded low pressure area that had a trailing frontal system that lay nearly stationary over northern California on the afternoon of the 16th, with continuous warm advection also ongoing in that area. Note that the lows tracked more or less just on or south of 40N.
This shows the diagram out of Weaver (1962, p. 5) he used to illustrate the Low-latitude type storm. Note the track of surface lows from south of 30N latitude in a (suggested) broad southwesterly flow in the middle and upper troposphere. This flow would be in a subtropical branch of the westerlies, with a marked split at about 160W longitude, the polar branch moving around a blocking high in the Gulf of Alaska. The track of the lows in the southern branch is key, as is the persistance of both the high latitude block, as is suggested by the verbatim "lifting" of his text from section 2-A-1 reproduced below. The short dashed lines south of the low trajectories indicate wave like frontal patterns (wave cyclones).
The prototype for the "pineapple connection" concept was the low-latitude type storm pattern associated with 1955 flood producing storms in northern and central California. The diagram above is a classic figure taken from page17 illustrating the trajectory of the lows in the southern branch emanating from regions at or around 30N latitude.
This is Weaver's diagram for the Mid-latitude type storm that most corresponds to what happened in the present storm pattern. Note the trajectory of lows on or around 40N, with the main low moving due north into the Gulf of aoaska. The wave-like perturbation on the trailing frontal zone shown on the last day indicates a second low (wave cyclone) forming. The difference in the present case is that the final low progressed southeastward rather than northward, but the trajectories of the distrubances plus the latitude at which they were moving all correspond most closely to the Mid-latitude type.
On page 10, Weaver states in describing the effects of the Mid-latitude "southerly" type on California "...high values of surface dew point result from an air trajectory from south-southwest from a low latitude..." In essense, this storm type can transport substantial water vapor to the coast of California, was the case in the recent storm event.