Weather Blog

Whatever happened to 45 and sunny?

Whatever happened to 45 and sunny?
You'd think after two weeks of being Mother Nature's punching bag, we'd get a break.

Maybe February?

In what's akin to having a double header scheduled the day after a 19-inning marathon, it looks like 2009 is going to start the way 2008 will end -- stormy -- with three decent storms scheduled to blow through here this week. In fact, we might pull off the hat trick of Northwest winter weather: flooding, snow and wind.

Of the three, it appears wind will become the biggest factor as we wade through the final days of '08, with perhaps the largest punch reserved for the start of 2009 as the third storm, due in Friday morning, is looking like the strongest of the week, and perhaps the strongest of the year as far as wind goes.

Why so stormy? The north Pacific Ocean is perfectly primed for storm generation. Remember all that cold air that we had? (If you need a reminder, check your street's curb.) It's still out there. Temperatures in Siberia have been in the -70F range of late, while the interior of Alaska is having *high* temperatures around -40 (C or F, take your pick) and that's an amazing amount of arctic air to tap into and shove to the east.

For the past two weeks, a ridge of high pressure out in the Pacific was helping to alter the jet stream so that it was pushing far north into arctic temperatures, then down along British Columbia, sending that arctic air into the interior, and having it available to be drawn into Western Washington by all those storms passing by to our west and south.

That ridge moved west, and now that cold air is pooling into the Gulf of Alaska and northern Pacific.  In the meantime, we have the typical warmer waters and air to the south as you approach the tropics. This stark difference in temperature and the boundary between is the machine that drives a strong jet stream and storm development in the mid-latitudes.

(That is unlike hurricanes, which feed off the heat from tropical waters to form, and thus why it's considered a tropical storm. Our big storms feed off the interaction between cold and warm air boundaries, which is why our storms are not considered hurricanes and not named, despite being sometimes capable of producing "hurricane-force" winds.)

Anyway, with the set up in place, forecasting models show some pretty strong storms developing this week and moving our way.

The first one is the weakest -- that's the one that's here Monday. That's just some rain and mountain snow. It's calling card might be that behind the front later Monday night, we could see some heavy showers knock the snow level down to about 500 feet or so -- especially in the Convergence Zone area.

That might be good for a inch of sloppy snow between Shoreline and Everett overnight, but this is not arctic blast, part 2. That snow will melt away early Tuesday morning as we climb well back into the 40s and no hard freeze is expected to make for any ice problems.

The next storm is due in Tuesday afternoon, with gusty winds developing late Tuesday evening into Tuesday night. Winds here look to be on par with the usual winter storm -- gusting 40-55 mph along the coast and north interior, and to 40-45 mph in the Puget Sound area.  The storm is about average in strength for this time of year, and expected to make landfall up on the northern tip of Vancouver Island, so far enough away to keep things manageable here.

We look cool and showery for New Year's Eve, and then all attention turns to our first full night of 2009.

This third storm is due in Thursday night into Friday morning and forecasting models have shown some signs that this storm should warrant attention. As usual this far out, there is some uncertainty in the storm, but there has been some consistency that this storm looks quite strong.

A few scenarios painted over the last three or four model outputs have even had the storm strength among the stronger we see around here, and have it come ashore somewhere between the northwestern tip of Washington and Central Vancouver Island -- a spot where our wind storms are the strongest.

Just checking one model run that just finished Monday morning as I type this, and it's still saying the storm will be quite strong, but going with a Central Vancouver Island track, which would still be quite windy, but maybe not historically windy. But as I said, this track has varied a bit -- and a track across NW Washington or southern Vancouver Island would make it worse.

(You can sort of get a handle of a predicted storm's strength by "counting the rings" on the forecast chart -- each black line on the map is one milibar of pressure. Count the lines between Bellingham and Portland. Anything over 15 is a pretty good ride; anything over 20 is getting up into record territory (largest one I've seen: 23.2 during Hanukkah Eve/Dec. 2006 storm)  This is not a perfect predictor of winds, but just a rough gauge.)

To top it off, these storms all have heavy rain along for the ride, so we'll have to watch the rivers for flood potential too as we could alternate periods of high snow levels/heavy rain in the warm sectors of these storms, then heavy mountain snow in the storm's wake as the cooler air moves in.

We will be keeping a close eye on this all week. Also, for all you severe weather fans, long range forecasts perhaps hint at a return to some colder weather again for around Jan. 7.  The current advertised scenario is not as bad as what we just went through, but suffice to say, winter still has plenty of time left.  And some of my resident long-range climate gurus see signs that they say point to another cold snap in late January/early February.

(Note to bosses: I plan on taking the entire month of March off to recoup :) )