Pacific Northwest, USA
The West Coast seems to have all kinds of disasters: Wildfires. Earthquakes. Volcanoes. Landslides.

One thing the West Coast doesn't have, though, is hurricanes.

The reason is simple. The primary ocean currents off the West Coast come from the north, bringing cold water down from Alaska. Any tropical systems that move northward from the Mexican coast lose energy as they move into colder and colder water.

Once in a great while, a tropical storm can make it close to San Diego, but none on record has made it farther north. But this past week, the Pacific Northwest experienced a storm that caused more destruction, death and hardship than many hurricanes have.

At least eight people have died in Washington and Oregon from the storm, with damage expected to reach the billions of dollars from flooding and high winds. Washington's governor said the tree damage was like nothing else he had seen since Mount St. Helens erupted in 1980.

The same storm brought less rain than expected to Southern California on Friday but was forecast to bring a swath of rain and snow to the nation's midsection over the weekend and early next week.

A strong northern Pacific low pressure system can be a fearsome beast. While never as intense as the worst hurricanes, the storms can have winds equal to many weak to moderate hurricanes, and those winds can cover a much greater area.

Late fall and early winter in the northern Pacific is a prime time to see storms like this develop, as the jetstream dips farther and farther southward after its summer retreat into the high northern latitudes. That allows cold air from the North Pole to sink farther south and collide with warm, moist subtropical air from the central Pacific.

The Pacific Northwest typically experiences one or two pretty large storms of this nature each year, but this last one was particularly severe, owing some of its strength to two typhoons whose remnants were pulled into the developing system. Thousands of people remained without power on Friday.