Friday, March 16, 2012

The Revenge of La Nina

 Forecast Update and More on La Nina on KPLU at 9 AM Friday or online.

Last winter we were securely in La Nina conditions and the region experienced a miserable, cold, wet spring that lasted into mid summer.   Horror to all soccer and Little League parents.

This winter we have also been in a La Nina and since early February we have been colder and wetter than normal, with snowpack surging in our mountains.

Yes, it appears we are dealing with  the revenge of La Nina.

Beware the white side of the force
So how bad has it been?


 Here is the plot of temperatures at Sea Tac versus normal highs and lows for the past month.  Only four days have equaled or exceeded normal, while a large number of days have been below normal. 
Here is the departure of temperature from normal for the past 30 days:  the western U.S. has generally been colder than normal (dark green and blue), with western WA and Oregon, MUCH cooler than normal.  Maddeningly, nearly all of the nation east of the Rockies had been much WARMER than normal.

Precipitation has been greater than normal over the Cascades and western WA, resulting in a rapid build up of snowpack.  As you can see from the snow water equivalent on March 15th, much of our area is above normal.  But CA is still in a snow drought.

Between the 9th and 14th of March, Mt. Baker  added 59 inches of snow and now is virtually tied with last year's total on the same date (251 inches on the ground today, 252 inches a year ago).  Take a look at the snow water for the Seattle watershed (Cedar/Tolt)--way above last year and normal.  We are already well above the normal winter max snowpack at that site.

The fascinating thing about La Nina years is how often we have seen this late winter surge of snow, cold, and precipitation.   You never give up in February...March is often a big snow month.

So what is going to happen?   Are we going to have to endure a non-spring like last year?
There is some suggestion that our fate is different than last year...we will suffer...but the wet, chill will not last into summer.

First, the suffering.  The last extended runs of the best modeling system in the world (the European Center), indicates that upper troughing with cold, wet weather will last for at least the next ten days.   In fact, we will get quite cool this weekend, with a chance of lowland snow in the Puget Sound convergence zone on Saturday morning (but nothing heavy) and low snow levels (roughly 500 ft) ocer the weekend.  That means higher hills could see some flakes....but no real accumulations until you get to 1000 ft.   Continued snow in the mountains.

But something is changing:  La Nina is rapidly weakening.  As shown in the next picture, the cold anomalies in the central tropical Pacific are rapidly declining and some parts of the tropical eastern Pacific are now warmer than normal.   Predictive models suggest that La Nina will be over by the end of April.

As explained in previous blogs, La Nina often forces ridging in the eastern Pacific and troughing over the NW--producing the cold/wet pattern.   By early summer the La Nina forcing should be over.

The NWS runs a climate prediction system four times a day that predicts the weather out several months.    Here is what it is showing for temperature.  A bit colder than normal for early Spring, followed by near-normal temperatures for late spring into summer.  Maybe, just maybe, we will get out this infernal pattern.

I am buying my tomato seeds this week! 

Jabba the snowman is not happy.

17 comments:

Madrona Tree said...

I'm in Bellevue and heard thunder 3x yesterday. Isn't that odd to hear during a hailstorm?

Lance said...

Thanks for posting about this. The cold weather the last couple weeks have brought up fears that we'll see another April/May like last year... I hope that's not the case, Jabba the Snowman would say otherwise.

Christina Wilsdon said...

I am no weather expert but as I recall hailstones form in the big tall turbulent clouds that also form thunderstorms. But even after 20-odd years of living in the NW, hearing thunder in winter still astonishes me--I grew up on the east coast and the only times we got thunder, and plenty of it, was in summertime.

Scott Souchock said...

With all the rain I was inspired to create the poster "Keep Dry and Carry On". You can see it at http://www.scottlook.com.

Scott said...

"Infernal" isn't the adjective I would use for cold and wet.

Brian W. said...

Thanks Cliff, for putting an analytical face on the recent misery. It truly has been dreadfully consistent in being cold, wet and dark. We are almost to equinox, but the sun hasn't had a clear shot at my face but for a few minutes of one day in the past many weeks.

What do we do but get up and try to sing the day into something positive, despite the clamped down weather.

Ferdi said...

La Nina makes a good scapegoat, but who remembers the last time we had a nice March? I have it in my unscientific head that March is one of the more disagreeable months of the year. But thanks for giving us some hope Cliff.

Placeholder said...

Thanks for the update, Cliff. Hope springs eternal!

dmg said...

"So how bad has it been?" A better saying for March should be; "How Awesome has it been" . This has been
quite an exciting month for the weather geeks out there. And the skiing has been A+++

Patrick said...

I like the Jabba the Snowman picture.

Olga said...

i'd cry, but no one can hear me over the heater fans...

Paul said...

It's snowing hard now on Queen Anne Hill. Not yet enough for a Jabba, but a lot for St. Patrick's Day.

Super Hip said...

Cliff -
It is currently snowing heavily outside of my house in Lower QA. Now, March might not be a typically "nice" weather month... but this? In my 14 yrs living here I've never seen this unlike in the Midwest where I grew up... where it happens to b 75 degrees and sunny today... I guess I no longer live in a mild, temperate climate anymore :(

Brad said...

Light snow and rain mixed with graupel South Tacoma 4 pm Saturday

Polistra said...

I had a feeling this would happen. Old Nina gets her licks in one way or another. She gave Spokane a record 1.2 inches of rain on Thursdsay.

However, it's still good that she waited till temps are fairly warm. The same precip in December would have been 20 inches of snow!

richard583 said...

May I make a suggestion, regarding your "tomato seed" selection. ? — A "cherry" type. (Not a sales pitch. Just gardener to gardener exchange.) "Burpee's", organic, "Chadwick Cherry". .. "Ace" Hardware stocks them here where I am more south. / Choice of "Allan" Chadwick, noted master horticulturist, father of the "Bio-Intensive" organic growing method, and in large part, responsible for introducing the idea of growing vegetables etc., more organically, to the "hippies", back in the later "sixties"; more formally, a Santa Cruz State University.

Steve said...

Thundersnow in Shoreline-- 8:4pm Sunday. Fun stuff.