What the Pacific Northwest Needs (Winters in the Pac NW)

[donsutherland1]

An important issue arose in another thread concerning the recent lack of cold and snowy winters in the Pacific Northwest. I'll post the response separately so that those who might have missed it but have an interest could read it.

In my view, what the West really needs is a winter where the PDO is strongly negative. The following is a composite of temperature anomalies during the 5 most negative PDO winters since 1948-49:



From 1945-46 through 1974-75, the winter PDO was negative in 24/30 (80%) winters. However, from 1975-76 through 2003-04, the PDO was positive in 20/29 (69%) winters.

Also, since 1900-01, there have been 16 winters where the PDO averaged -1.000 or below. Those winters fared as follows:

• Colder than normal: 11 (69%)
• Near normal: 1 (6%)
• Warmer than normal: 4 (25%)

Of those winters, there were 8 that saw the PDO average -1.50 or below:

• Colder than normal: 7 (87%)
• Warmer than normal: 1 (13%)

[andrewr]

Nice info as always Don. Hopefully a shift comes soon because a week from now they may declare a drought for Washington (not that it really needs to be declared). Any information regarding precip. amounts and its correlation to the PDO? http://www.king5.com/topstories/stories ... d0d3e.html

[donsutherland1]

Andrew,

A strongly negative PDO-La Niña combination is usually a wet one. Since 1900-01, 11 winters have seen the PDO average -1.000 or below at the same time La Niña conditions were present. In terms of December-February precipitation, they fared as follows:

• Wetter than normal: 9 (82%)
• Drier than normal: 2 (18%)

Neutral or El Niño conditions along with a strongly negative PDO generally translate into normal or below normal precipitation. Since 1900-01, there have been 5 such winters:

• Wetter than normal: 1 (20%)
• Near normal precipitation: 1 (20%)
• Drier than normal: 3 (60%)

Winter 2004-05 saw a weak El Niño. A moderately negative PDO was in place in December but then the PDO switched to positive in January. FWIW, ENSO analogs suggest that March will likely see below normal rainfall in the Pacific Northwest. There may be some hints of change for April, but this is not yet certain.

[W13]

Great anaylisis Don, I always love your posts. they are so informative.

I just hope that within the next few years, the PDO once again goes negative around our area. It seems that that is what makes or breaks a food winter in the Pacific Northwest.

[snow_wizzard]

That is fabulous Info Don! A different take is always useful.

Do you have a link where we could look at the PDO index? This is one area I am not really strong on. I have focused more on PNA, AO, El Nino / La Nina, OLR, and MJO.

[Guest]

a food winter? LOL... Yeah I really hope we get a good negative PDO winter here soon... We really need it... By the way, I LOVE YOUR POSTS THEY ARE AWESOME... learn so much from them.

[donsutherland1]

Snow_wizzard,

The PDO can be found at: http://jisao.washington.edu/pdo/PDO.latest

[donsutherland1]

Thanks W13.

LarryWx, who posted on Atlanta's snow dates around 3/11-14, has done some research that indicates that we might be at the beginning of a new long-term negative PDO period. The October-December PDO was negative for three consecutive months and that might represent a warning shot of what lies ahead. At the very least, we're probably in a transition that will lead to such a period where the PDO is predominantly negative.

[snow_wizzard]

Thanks Don! You have made my day. Our cold winters may return very soon now. Thanks for the link too!

What is your take on the running PNA average going below zero a couple of years ago?

[donsutherland1]

Snow_wizzard,

It's still difficult to say whether next winter or the one after will see the negative PDO lock in. But I do expect this to happen at some point this decade and probably sooner rather than later.

As for the running average of the PNA, it's having gone below zero could be another hint of the changing PDO regime. A negative PDO sees a much higher tendency for PNA- situations.

[Guest]

This is great news Don... For so long we have been finding bits and pieces of evidence to support the possibility of an overall change in the weather pattern here in the northwest, and the rest of the world as well. The one piece of significant evidence we didn't have really was about the PDO average over the past 50+ years and how it seems that we are headed towards another overall negative PDO average. If this happens it is the icing on the cake for our winters here in the Northwest.

[Brian_from_bellingham]

Don, is there any way that PDO's can be predicted, other then general trends? I know they predict El Nino/La Nina pretty well, it would be great if they could predict this as well. From what I have read of it, we have been overdue for a longer term negative phase, but it seems like not a lot is understood, and predictions are difficult.

[donsutherland1]

Brian,

I'm not aware of any predictions that are made for the PDO as is the case with regard to the ENSO. However, some of the modeling that addresses SSTAs e.g., the CFS, might offer some idea as to what lies ahead. Again, those very long-range models are far from perfect.

Research is ongoing in the longer-term PDO cycles.

[TT-SEA]

Don-

As you know... this amazing blocking pattern that has given California so much rain and the East Coast so much snow has left the Pacific Northwest in a drought.

Any thoughts on whether this coming spring and summer will be cooler and wetter up here??

If we have another hot, dry summer we are in BIG trouble.

[azsnowman]

Trust me.......IF I could SEND ALL this moisture WE'RE having, I "WOULD".......I can honestly say, with the utmost sincerity, "ENOUGH!" The drought here in Az for all intents and purposes, has been quashed for the time being, the bark beetle problem is finished and now, any moisture that is falling is going to *waste*, the ground here in Northern Az is SO saturated, it cannot take another DROP and the NWS has 2" of RAIN for us AGAIN this weekend. "PLEASE, would SOMEONE come and TAKE all this RAIN??"

Dennis

[donsutherland1]

TT-SEA,

There are some indications that April might be wetter in the Pacific Northwest after a dry March and perhaps see above normal rainfall (though not necessarily excessive rainfall). However, when it comes to the summer, the emerging analogs seem to be pointing to near normal rainfall with perhaps somewhat warmer than normal temperatures. Right now, at least for me, it's too soon to make a call for the summer. The March and April ideas look stronger at this point in time.

[snow_wizzard]

Don...This is a little off topic, but how do you become an S2K Forecaster?

[donsutherland1]

Snow_wizzard,

I was invited to become one by the administrators/moderators. You might want to check with them on the criteria that they use.