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2012 enso thread


uncle W

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it could linger for a third year or become an el nino...I'll start with el nino years...there are 19 el nino years since 1950...hopefully next year will be one...these are the years and strength...

winter...peak ONI...peak period...

1977-78.....0.7.....ONDJF

1976-77.....0.8.....OND

1969-70.....0.8.....OND

1951-52.....0.8.....SON

2004-05.....0.9.....ASO

1963-64.....1.0.....ONDJ

1968-69.....1.0.....DJFM

2006-07.....1.1.....ONDJ

1986-87.....1.3.....JFM

1994-95.....1.3.....NDJ

2002-03.....1.5.....OND

1965-66.....1.6.....OND

1987-88.....1.6.....JASO

1957-58.....1.7.....DJF

2009-10.....1.7.....DJF

1991-92.....1.8.....DJF

1972-73.....2.1.....NDJ

1982-83.....2.3.....NDJF

1997-98.....2.5.....ONDJ

the top seven had ...three great winters...three very good ones and one mediocre...

the middle six had one great winter...three mediocre and two duds...

the bottom six had two great winters...one good and three duds...

Some forecasts are for a neutral enso next winter...I'll post the neutral years another time...

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the 22 neutral years...

the eight lowest years...

year....peak index

1983-84.....-0.9.....OND

2008-09.....-0.8.....DJF

2005-06.....-0.7.....NDJF

1966-67.....-0.6.....FMA

1961-62.....-0.6.....ASON

1959-60.....-0.5.....JAS

1980-81.....-0.5.....JFM

1985-86.....-0.5.....DJF

1978-79.....-0.4.....MJJASO

1981-82.....-0.4.....JJAS

1996-97.....-0.4.....NDJF

1989-90.....-0.3.....JJASON

1960-61.....-0.2.....SONDJFMA

2001-02.....-0.1.....ONDJF

1990-91......0.4.....NDJF

1993-94......0.4.....MAMJ

1952-53......0.5.....FMAMJJ

1953-54......0.5.....DJF

1958-59......0.5.....JFM

1979-80......0.5.....ONDJF

2003-04......0.6.....OND

1992-93......0.8.....AMJ

the lowest eight winters had one great winter...three good ones...three mediocre...one dud...

the middle six winters had one great winter...two good ones...three duds...

the higest eight winters had two great winters...one good...one mediocre...four duds...

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The ENSO state won't matter much if we don't get back into the -AO/NAO phase that had been so frequent every winter other than 07-08 the last few years. This winter IMO was destined to be a +NAO early due to the relatively widespread below normal SSTs between Greenland and Iceland headed into mid-Autumn. The question is what would have happened to that pool of water had we not had the Stratospheric ice age event that ultimately led to those regions going insanely cold and enhancing the coolness of that area. Its highly possible we may have had a +NAO through mid December or so and then may have seen a reversal but that ice age across the northern regions basically killed any chance of that and also resulted in the +AO.

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the La nina years...weak to strong...21 years...

year.....peak ONI index...

1962-63.....-0.7.....ONDJ

1995-96.....-0.7.....ONDJFM

2000-01.....-0.7.....NDJ

1956-57.....-0.9.....SOND

1967-68.....-0.9.....JFM

1974-75.....-0.9.....OND

1950-51.....-1.0.....NDJF

1971-72.....-1.0.....OND

1984-85.....-1.1.....NDJ

1964-65.....-1.2.....SOND

1954-55.....-1.2.....ASO

1970-71.....-1.3.....DJFM

2007-08.....-1.4.....DJFM

2010-11.....-1.4.....SONDJ

1998-99.....-1.6.....NDJF

1999-00.....-1.6.....NDJF

1949-50.....-1.7.....DJF

1975-76.....-1.7.....ONDJ

1988-89.....-1.9.....ONDJ

1955-56.....-2.0.....OND

1973-74.....-2.1.....NDJ

top six weakest...Middle eight...seven strongest...

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Just out of curiosity, what makes a weak nino so good for cold in the northeast? I know a nino excites the STJ, but how would that cool things so dramatically in its weak phase?

Negative NAO's are dominant in weak ninos - that's the primary factor for the cold. El Nino generally creates a more favorable stratospheric environment with a weaker vortex, promoting more high latitude blocking than La Nina events. Additionally, strong ENSO tends to overwhelm the pattern for much of the CONUS (assuming you don't have a raging -NAO/AO like 2009-10). Hence why weak to mod El Ninos are very good for the mid atlantic up through SNE. Tendency for blocking, active sub tropical jet stream, yet the Nino is not powerful enough to throw a ton of warmth into the regime.

So essentially it comes down to being a conducive preset condition for the development of neg NAO patterns.

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Negative NAO's are dominant in weak ninos - that's the primary factor for the cold. El Nino generally creates a more favorable stratospheric environment with a weaker vortex, promoting more high latitude blocking than La Nina events. Additionally, strong ENSO tends to overwhelm the pattern for much of the CONUS (assuming you don't have a raging -NAO/AO like 2009-10). Hence why weak to mod El Ninos are very good for the mid atlantic up through SNE. Tendency for blocking, active sub tropical jet stream, yet the Nino is not powerful enough to throw a ton of warmth into the regime.

So essentially it comes down to being a conducive preset condition for the development of neg NAO patterns.

Yeah that makes sense, the AO/NAO tandem is the only thing that could deliver cold on that level.

If you dont mind explaining more, how do ENSO conditions alter stratospheric circulation near the poles in this case, since were talking about a weak vortex, how does the ENSO slow it down?

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Negative NAO's are dominant in weak ninos - that's the primary factor for the cold. El Nino generally creates a more favorable stratospheric environment with a weaker vortex, promoting more high latitude blocking than La Nina events. Additionally, strong ENSO tends to overwhelm the pattern for much of the CONUS (assuming you don't have a raging -NAO/AO like 2009-10). Hence why weak to mod El Ninos are very good for the mid atlantic up through SNE. Tendency for blocking, active sub tropical jet stream, yet the Nino is not powerful enough to throw a ton of warmth into the regime.

So essentially it comes down to being a conducive preset condition for the development of neg NAO patterns.

Isotherm,

Whereas I agree about the significant cold influence of a -NAO tendency in weaker El Nino's, I think that there is a good bit more to it than just the -NAO tendency toward making weak Nino's so cold on average in the E US. I feel that there is a good bit of a tropical forcing contribution to E US cold from the weak Nino, itself. My reasoning is explained here:

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