PDO most likely nuetral this winter

[Brian_from_bellingham]

I would not normally challenge a pro like Don Sutherland, but he is most likely wrong about the PDO being positive this winter. Says who? The University of Washington, who first "discovered" the PDO and are the ones who have tracked it and monitered it for years. Here is what they say:

"North Pacific SSTs have projected onto the warm (positive) phase of the PDO pattern for every month in 2005 (January-July), although the trend since May has been to weaker positive values. Notably, nearshore ocean temperatures off the coast of southern British Columbia to central California cooled considerably from exceptionally warm levels in May through mid-July to near average and even below average values from late July through present (August 18) (read related Seattle Post-Intelligencer story).

If ENSO forecasts favoring ENSO-neutral conditions in the next 3-6 months are correct, the ENSO influence on North Pacific SSTs should be expected to contribute to a continuation of recent trends toward near-zero values of the PDO index for the next 3-6 months"

Many people have not noticed the MAJOR change in the SST anomalies off the west coast from BC to Oregon, from WAY above normal to now below normal. As long as SST's off the coast are below normal, there will not be a positve PDO. I cannot predict whether or not it will be a negative PDO, but with the winds continuing to cause upwelling, there is no sign of a warmup in the SST's in that region, so no chance of a positive PDO developing.

http://www.cses.washington.edu/cig/fpt/cloutlook.shtml
http://seattlepi.nwsource.com/local/236883_ocean17.html

[Brian_from_bellingham]

Is is now at +0.25, which is officially neutral.

Someone at another chat sight came up with the following statistic:

There were 14 years when the PDO was in the 0.0 - +0.5 range in August after a drop the month before. Of these winters-

5/14 (36%) of the following winters saw a +PDO
9/14 (64%) of the following winters saw a -PDO

And:

7/23 (30%) of the years that saw an August PDO between 0.0 and +0.5 saw a + PDO winter
16/23 (70%) of the years that saw an August PDO between 0.0 and +0.5 saw a -PDO winter

This is strange, considering what we saw earlier in the year, and that most of the time under those circumstances the PDO was positive the following winter. Maybe there is going to be a phase change in the PDO, as others have speculated.

Anyway, this generally does not mean anything for anyone outside the northwest, as PDO is much more of a local phenomenon, so don't think that I am trying to say the east will not be cold this year. But it is good news for those of us in the NW.

[weather girl]

Interesting (?) side fact: We were watching the Oregon Department of Fish and Wildlife sane (net, count, weigh, measure, free) Salmon along the Rogue just off the Southern Oregon coast at the end of August. The run was incredible. The ODFW told us it was a sign that the Pacific had cooled in August. Actually, they said "cooled significantly". The August run was much better than last year and at any point over the summer.

I just think you're right about the PDO. It's more cool than warm out there.

[Brian_from_bellingham]

And that is quite a drastic change from before, when I had read articles about how there were few fish because the waters were warm. I wish they had more data for that area, I know they use satellites instead of bouy's, and I have never seen any charts about what the waters are doing just below the surface. But I think that the PDO is more nuetral will help our chances of at least some cold weather this year.

[donsutherland1]

Brian_from_bellingham,

I'm thinking the PDO will generally range between 0 and +0.50, so the differences between UW and I might not be all that great even as I refer to its being positive; In any case, I'll be re-assessing my expectations to see if they still hold based on the latest data prior to my winter forecast (mid-October).

FWIW, while a warm ENSO more often than not sees a PDO+ during the winter, the relationship is not so strong that one can absolutely depend on it. 10/26 (38%) cases since 1950 had a cool ENSO (per MEI)/PDO+ combination for the winter (December-February).

Also, since 1950, there have been 7 summers that saw the following, which has occurred in 2005:

∙ June PDO: +0.75 or above
∙ Fall in August of 0.40 or more

Finally, in 11/12 (92%) of winters that followed a June PDO of +0.75 or greater, the winter PDO averaged positive.

In short, barring some dramatic changes in the recent data, I'm reasonably confident in my above prediction. I'll be interested to see if the new data (including September data) will change this. But, odds seem pretty strongly against a PDO that averages < 0 for the upcoming winter. Of course, it could be < 0 during a given month, but that's a different matter.

All 7 wound up with a PDO > 0 during the following winter.

Best wishes.

[donsutherland1]

Brian_from_bellingham,

I usually take at least 3 months data so as to avoid the risk of error from temporary fluctuations. Hence, I referred back to June (which was the key difference in assessing June-August).

Looking ahead, by October 8/9 (89%) of the aforementioned seasons that saw a negative PDo for the winter had a monthly PDO < +0.150. In contrast, all 5 of the seasons that saw the positive winter PDO had a PDO of +0.150 or above in October. Thus, October might well provide an important hint as to how things are evolving.

Time will tell.

[JBG]

I had thought we've been in a "cool phase" of PDO since the 1997-98 Super El Nino broke. Am I wrong?