A little rain, followed by the big dry

November should be one of the stormiest, wettest months of the year in our region.

Not this year.

So far this month, we have only had about .76 inches, roughly 2.5 inches below normal.  Here is the plot of cumulative precipitation at Seattle (cyan is normal, purple--what actually fell)...pretty pathetic.

This weekend, a modest atmospheric river will bring substantial rain to British Columbia, but only the norther portion of Washington will get much moisture. Another storm comes in Monday.  But then it all dries out for an extended period of time....let's call it the big dry.  Very unusual considering the time of the year--with the last two weeks of the November being the wettest climatologically for our region.

The incoming atmospheric river looks mighty impressive on the latest infrared satellite imagery, drawing moisture all the way from the tropics.  Since it passes near Hawaii, I guess we can also call this a pineapple express.

The total precipitation through 4 AM on Monday is very impressive in British Columbia (over 5 inches in places),  but it fades progressively to the south.

But after one more storm late Monday/early Tuesday, things dry out.  Here is the total precipitation for the three days ending Friday at 4 PM.  Nothing over western WA and southwest BC.

And the highly prized European Center ensemble prediction  of accumulated precipitation anomaly (difference from normal) for the next 15 days, indicates much drier conditions than typical--by 2-6 inches.  Good for raking leaves (I hate soggy leaves).

Why this dry boon?   Persistent ridging (high pressure) over the West Coast (see below for 500 hPa--about 18,000 ft).  Orange shows much higher than normal heights/pressures.

Why is this happening?   The answer is clear: you have to expect fine weather after the Seattle Times does a big story on how gloomy it is here in Seattle.

Slow Start to Winter Snow Season

After the extraordinary early snow during the first half of October, many skiers and snowboarders were greasing their skies and prepping their gear for an early start of the snow recreation season.

But alas, things did not work out that way.  Warmer temperatures followed and then starting October 25th, we entered a 14-day dry streak.  Most of the snow melted, leaving us worse than a year ago.  To illustrate, compare the snow depth today and one year ago (see below).  The north Cascades and southern BC had much more snow at higher elevations in 2018.

 

So what about this year?  We have had a "problem"--persistent high pressure over the northeast Pacific.   To illustrate here is the height anomaly (difference from normal) at 500 hPa (about 18,000 ft) for the past 30 days.  Red indicates higher heights (higher pressure/ridging), blue indicates troughing (lower than normal heights).  A strong persistent pattern that explains the dryness and warmth of the West Coast and the cool/wet weather of the eastern US, since ridging brings drying and troughing, the opposite.

The forecast for the next five days for the same level?  A big ridge over the west coast (the shading is the anomaly, with orange being higher than normal).  This is a wetter pattern, but relatively warm.  Not good for snow.

The latest 7-day accumulated snow forecast from the UW system provides some snow at the highest elevations over the north Cascades, but even there only 6-12 inches.

Strangely enough the persistence of this ridge could be a good thing for snow later in the season--if the ridge moves back towards the west, we might be open to a trough coming from the north, like last February.  We will see. 

The media has been full of winter weather forecasts, the skill of which is marginal at best.