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La Niña/Winter 2016-17 Discussion


dmillz25

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The Euro is currently much weaker. ENSO neutral to weak La Nina conditions by summer.

It keeps the +PDO so strong that it wraps around the cooling SST's along the equator.

ECMWF model 0.9 0.3 -0.2 -0.4 -0.4

EURO.png

Thoughts on the shifting of the subtropic high, SE flow in response to the developing La Niña? That is probably going to give a big hit to the +PDO. I can see the PDO really dropping off towards neutral or even negative...
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Models currently going for the 3rd La Nina to develop since 1950 with such a

strong +PDO. The only two years with an official La Nina and a +PDO were

84-85 and 95-96. 83-84 and 05-06 were too weak to make official La Nina

status but had a few trimonthlies with weak La Nina conditions.

NMME_ensemble_tmpsfc_season5.png

sst.png

We all know how 95-96 was wih snow that year but what about 84-85?
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Models currently going for the 3rd La Nina to develop since 1950 with such a

strong +PDO. The only two years with an official La Nina and a +PDO were 

84-85 and 95-96. 83-84 and 05-06 were too weak to make official La Nina

status but had a few trimonthlies with weak La Nina conditions. 

 

attachicon.gifNMME_ensemble_tmpsfc_season5.png

 

attachicon.gifsst.png

1984-85 was cold for one month only...1983-84 was a cold winter but had a warm February...05-06 was the warmest of the four...

la nina winters...DJF ONI...A.T....min....30 day cold...snowfall...biggest snowfalls...

1995-96..............-0.9.......32.3.....5..........27.7..........75.6"..........20.2" 10.7" 7.9" 7.5" 4.6" 4.6" 4.1"

1983-84..............-0.5.......35.2.....4..........26.1..........25.4"..........6.9" 5.1" 4.6"

1984-85..............-0.9.......36.4....-2..........27.5..........24.1".........5.7" 4.8" 4.3" 4.1"

2005-06..............-0.7.......37.3...14..........33.5..........40.0"..........26.9" 5.8"

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A really impressive increase in the PDO from February to March.

 

March 2016 is in a virtual tie with 1941 for the strongest March +PDO on record.

 

It will be interesting to see how far the La Nina can progress with the PDO

near record levels for this time of year. The last two years were already

the strongest since the 1980's.

 

http://research.jisao.washington.edu/pdo/PDO.latest

 

2016** 1.53 1.75 2.40

 

attachicon.gifPDO.png

1941 went on to have another el nino for a third straight year...

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I assume the PDO will certainly alter how the season progresses compared to the last Nino to Niña transition in 2010 along with current strength and duration of Nino.

Perhaps Bluewave has the 500mb heights, but I believe a mean Ridge was located over Ohio Valley and led to relatively low humidity but big heat for spring and summer.

Would love a warm season like that.

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Kind of interesting that the strongest trades have been closer to the coast of South America

and Atlantic rather than from the WPAC to DL like we often see at the onset of La Nina.

 

attachicon.gifu.anom.30.5S-5N.gif

 

 

This explains why the eastern regions have cooled so quickly, while the central regions have still remained warm (at the surface).

 

In 1998, the eastern regions were still holding on strong, while the central and western regions were collapsing.

 

post-73-0-74576900-1461773225_thumb.gif

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Yeah, the only El Nino to La Nina spring transition that looks remotely similar is 1995. That

El Nino ended with a strong cooling in the eastern ENSO regions with stronger trades closer

to the South American coast also. While the PDO was rising during that spring, this year is

much stronger. So this super El Nino continues to rewrite the playbook even as it's fading out.

Like you mentioned, the 97-98 super El Nino held onto the warmer waters east and the

strongest spring trades focused further west back to the WPAC and DL.

MAY95SST.png

MAR95W.png

If the model projections are correct, central and western ENSO regions will follow the eastern regions' lead shortly and really begin to crash as trades strengthen and the +SOI climbs. The continued development of a strong -IOD support this continuing with the associated pressure patterns
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Models currently going for the 3rd La Nina to develop since 1950 with such a

strong +PDO. The only two years with an official La Nina and a +PDO were

84-85 and 95-96. 83-84 and 05-06 were too weak to make official La Nina

status but had a few trimonthlies with weak La Nina conditions.

NMME_ensemble_tmpsfc_season5.png

sst.png

There has never been a moderate or strong La Niña along with a +PDO as long as weather records have been kept. Most forecast models and experts at this point are calling for at least a moderate La Niña. So if the scenario of a +PDO and a moderate or strong Niña were to occur, it would be the first time in history and thus there would be no analogs for such a setup. My guess continues to be a transition to a -PDO or at least a neutral PDO by the end of fall. JB's thinking is that we go into a -PDO. It will be very intriguing either way
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Very unique situation shaping up as the La Nina develops heading into summer.

As we are getting near the end of the spring forecast barrier, the guidance is

coming in stronger with the La Nina forecasts. It looks like the model consensus

is indicating the potential to cross the moderate -1.0C La Nina level.

The models all insist on maintaining the strong +PDO signature as the La Nina

develops. This would be a first since 1950 with so much warm water in the

Eastern NPAC off the West Coast of North America. So it will be interesting

to see how things go. Even in the few years like 84-85 and 95-96 with

a +PDO, the warm water off the West Coast was much less impressive

than we are seeing in current forecasts. The other interesting note is

how much warmer the Eastern IO region now is compared to typical

La Nina development.

11 year -1.0 or lower peak trimonthly moderate La Nina composite

SST.png

Forecast is something new for post 1950 with so much SST warmth of Western North America

and Eastern IO

NMME_ensemble_tmpsfc_season1.png

Yes. The models continue to get stronger with the Niña with each run, as you said. Consensus is now for at least a solid moderate Niña with some even showing a "super" Niña (colder than -2.0C in region 3.4 come fall). As far as the Indian Ocean, a strongly negative IOD is developing, which is very favorable for strong trade winds and +SOI, which only serves to strengthen the Niña even more. Here is the classic -IOD ssta setup, which is what we are seeing now: https://www.google.com/search?q=negative+iod&prmd=insv&source=lnms&tbm=isch&sa=X&ved=0ahUKEwjzyPqo88_MAhWDwj4KHSpRCHsQ_AUICCgB&biw=320&bih=460#imgrc=q5IzQJjwp3emVM%3A
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