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ENSO Update and Other Matters

By Joe D'Aleo
Monday, April 27, 2009


The second year La Nina appears to be coming to an end. There is uncertainty as to whether we bounce to a weak El Nino or just neutralize before returning to La Nina which is favored near solar minima. There were two El Ninos near solar minima in the last 60 years that were brief and weak and were surrounded by La Ninas, which tend to dominate near minima.

 

The Multivariate ENSO Index (MEI) developed by Klaus Wolter at NOAA CDC shows we were in February and March still in La Nina territory.

But the ocean has warmed through the ENSO regions. The eastern region, NINO12 has warmed the most, much as it did last spring and summer. Warm water last year moved gradually west and eventually reached region NINO34 before fading. Notice also the blip up in the ocean heat content in the tropical Pacific ENSO region peaking in July before rapidly cooling again with levels almost as low as 2007/08 winter minimum.

There is some similarity to the spring of 2008 also in the cross section along the equator in the Pacific shown here. This year is on the left, 2008 on the right. Note the strip of warmth extending from deep in the western Pacific to the eastern Pacific surface waters. This represents a slight suppression of the thermocline.

See how it has changed in recent weeks in this animation. The reservoir of warmth in the west is less than last year.

 

The latest set of ENSO models suggest a continued warming of the tropical Pacific ENSO34 region with the majority of models in the neutral La Nada with temperatures between +0.5C and -0.5C. A few models go to an El Nino state. In general the dynamical atmospheric/oceanic coupled models are warmer than the statistical models.

 

 

 


 

Seasons (2009-2009)

Model

AMJ

MJJ

JJA

JAS

ASO

SON

OND

NDJ

DJF

Dynamical models

NASA GMAO model

0.2

0.7

1.2

1.4

1.6

1.6

1.6

1.6

1.5

NCEP Coupled Fcst Sys model

-0

0.2

0.4

0.4

0.5

0.6

0.8

 

 

Japan Met. Agency model

-0

0.2

0.3

0.4

0.4

 

 

 

 

Scripps Inst. HCM

-0.7

-0.6

-0.3

-0.1

0.1

0.2

0.4

0.5

0.6

Lamont-Doherty model

-0.4

-0.4

-0.4

-0.5

-0.5

-0.5

-0.5

-0.5

-0.4

POAMA (Austr) model

0

0.3

0.6

0.8

1

1.2

 

 

 

ECMWF model

0

0.2

0.4

0.7

 

 

 

 

 

UKMO model

-0.5

-0.2

0.1

 

 

 

 

 

 

KMA (Korea) SNU model

-0.2

0

0.2

0.3

0.4

0.5

0.6

0.6

0.6

ESSIC Intermed. Coupled model

-0.1

0.1

0.2

0.3

0.3

0.3

0.3

0.3

0.2

ECHAM/MOM

0.2

0.3

0.3

0.2

0.1

 

 

 

 

COLA ANOM

-0.5

-0.3

-0.1

0

0.1

0.2

0.5

0.9

1.1

MÉTÉO FRANCE model

-0.4

-0.2

0

0.2

0.4

 

 

 

 

COLA CCSM3 model

-0.1

0.3

0.7

0.9

0.9

0.9

1

1.1

1.2

Average, dynamical models

-0.2

0

0.2

0.4

0.4

0.6

0.6

0.6

0.7

 

 

By far the warmest model solution is the NASA GMAO followed by the COLA CCSM3. The Australian POAMA also went to El Nino levels by summer.

 

In contrast the statistical models shown below weakened to La Nada or stayed at a weak La Nina at least this summer.

  

 

Statistical models

NCEP/CPC Markov model

-0.7

-0.6

-0.5

-0.5

-0.5

-0.5

-0.4

-0.3

-0.2

NOAA/CDC Linear Inverse

-0.7

-0.6

-0.6

-0.5

-0.5

-0.4

-0.4

-0.3

-0.3

NCEP/CPC Constructed Analog

-0.4

-0.3

-0.3

-0.3

-0.3

-0.2

-0.1

-0.1

-0.1

NCEP/CPC Can Cor Anal

-0.4

-0.4

-0.3

-0.2

-0.2

-0.1

-0

0.1

0.1

Landsea/Knaff CLIPER

-0.3

-0.2

-0.2

-0.1

-0.1

-0.1

-0.1

-0.1

-0.1

Univ. BC Neural Network

-0.3

-0.2

-0.1

0

0.1

0.1

0

-0.1

-0.1

FSU Regression

-0.5

-0.4

-0.4

-0.4

-0.4

-0.5

-0.5

-0.5

-0.5

TDC - UCLA

-0.2

-0.1

-0

-0

-0.1

-0.1

-0.2

-0.3

-0.3

Average, statistical models

-0.4

-0.3

-0.3

-0.3

-0.2

-0.2

-0.2

-0.2

-0.2

Average, all models

-0.3

-0.1

0.1

0.1

0.2

0.2

0.2

0.2

0.2

 

The two years where an El Nino came on near solar minimum were 1965 and 1976. This is what the following summers and winters were like.

 

 

 

My best guess now is that we have a weakening La Nina that gets to a borderline El Nino state that IF the solar doesn’t bounce back sharply (unlikely) would revert back neutral to weak cool again next winter.

 

 

ONE OTHER ITEM OF BUSINESS

The stratospheric warming that took place late this winter was record breaking. But the impacts it had on surface weather was episodic and occurred only when it penetrated down to 500 mb and below as can be seen in this cross section.

When it reached down into the stratosphere is when the AO dipped and temperatures cooled the most. Also to note, that unlike in years where strong stratospheric vortex keeps cold air trapped over high latitudes that gets unloaded when a warming occurs and the AO crashes, this year, the arctic vortex was split and cold air was not trapped and in fact the mother load was pretty much already gone when the warming occurred. The high pressure that built up due to the ridging was polar in origin and not pure arctic or Siberian.  My forecast for a grand finale based on the super stratwarm did not verify perhaps for that reason.

 

Stratospheric warmings are more favored near solar max with west QBO and to a lesser degree near solar minimum with an easterly QBO (the case next winter). This might argue for an early winter. We will revisit as the ENSO and other factors progress.

 

The arrows point to period when warming reached the 500 mb level favoring blocking and most of the time, a negative AO.

 

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