First, let me start with an impressive water vapor satellite image that shows the amount of water vapor in the upper troposphere, with green being the most, followed by white, gray and black. Amazing spiral, with intervening layers of moist and dry air spiraling in towards the center.
The infrared satellite picture (giving the temperature and thus the height of the clouds) shows the spiral, with the speckled clouds indicating cold air moving into the system.
Hurricanes form over tropical waters and require a warm, moist environment....dry and cold air spiraling towards the storm center would kill it.
Then there is the energy source of the Sunday storm and hurricanes. Very different. Midlatitude storms derive their energy from horizontal temperature contrasts (or gradients). Hurricanes need warm water (more than roughly 80F), which provides both sensible heat and moisture. You know what the temperature of the eastern Pacific off our shore is right now? As shown by the NOAA sea surface temperature map, around 10C (50F). No true hurricane could survive over the northeast Pacific.
Hurricanes have sustained winds exceeding 64 kt (74 mph). Sustained winds NOT gusts. During the height of our storm, the strongest sustained winds were roughly 25-35 kt, with a few locations with the best exposure (like West Point, Seattle) getting into the 40s kt. Not even close to hurricane levels. For example, at the extremely well exposed UW Atmospheric Sciences site (on top of a 7 story building), sustained winds only reached around 25 knots (see below), with gusts hitting about 40 knots.
I could provide more illustrations and reasons, but the facts are clear. Sunday's storm was not a hurricane, did not have winds even close to that of a hurricane, didn't have the structure of a hurricane, and derived it energy from a very different source. Completely different animal from the tropical hurricanes striking the SE U.S.
Yesterday I talked to an experienced arborist, who told me that one reason so many trees fell during this event was due to the extraordinary saturation of our soils after the wettest winter in Seattle history.