# Presentation: 226780

## A review of

**A review of**
**2005/2006 ENSO Predictions**
- Tony Barnston
- Lisa Goddard
- Shuhua Li
- International Research Institute
- for Climate and Society (IRI)

## *            *           *            *

- *La Nina, Dec-Mar ’05-06

- *El Nino, October ‘06

- Two Events of Interest: A brief La Nina(*), and a “new” El Nino (*)

## Slide 3

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- Last week’s SST anomaly

## Slide 5

## Renewed, east-extended westerly wind anomalies

## mid-Oct ‘06

##           **     *

-           **     *

## *

- Climate
- Prediction
- Center
- NCEP

## *

- From Climate Diagnostics Center, Boulder, Colorado

**Black: This year**

## The onset of La Nina conditions in 

- December 2005, after a largely
- ENSO-neutral northern autumn,
- was unprecedented since 1950.
- How did it emerge?

## ←

**H**

**H**

**Sep 2005**

**L**

-  **e q u a t o r------------**

- Colombia

- Peru

- 110W

- Precursor to **Brief La Nina Conditions** in late 2005

- Note: Vern Kousky
- says this anticyclone
- is spurious, due to
- Reanalysis biases.

## ←

**H**

**H**

**H**

**Oct 2005**

-  **e q u a t o r------------**

- Colombia

- Peru

- 110W

- Precursor to **Brief La Nina Conditions** in late 2005

- Note: Vern Kousky
- says this anticyclone
- is spurious, due to
- Reanalysis biases.

## ←

**Nov 2005**

**H**

**H**

**H**

**L**

**H**

-  **e q u a t o r------------**

- Colombia

- Peru

- 110W

- Precursor to **Brief La Nina Conditions** in late 2005

- Note: Vern Kousky
- says this anticyclone
- is spurious, due to
- Reanalysis biases.

## *

- Five-Day Zonal Wind, SST, and 20o Isotherm Depth Anomalies along Equator
-            Zonal Wind                            SST                       20o Isotherm Depth

- Mid-2005 to Mid-2006: Brief La Nina Conditions

## How did statistical and dynamical ENSO

**prediction models fare regarding the ****brief**
**2005-06 La Nina conditions**** and the ****late**
**2006 El Nino development****?**

## Cool

- Conditions
- Coming

## Cool

- Conditions
- Coming

## Cool

- Conditions
- Coming

## El Nino

- Conditions
- Coming

## El Nino

- Conditions
- Coming

## El Nino

- Conditions
- Coming

## .

## .

- -----------------------------------------------------------------------------

## .

- -----------------------------------------------------------------------------

- Unanticipated
- by stat models

## .

- ---------------------------------------------------------------

- ---------------------------------------------------------------

- Unanticipated
- by stat models

## .

- *

- Hybrid Models:
- Dynamical
- ocean,
- statistical
- atmosphere

- Blue asterisk *
- means the model
- did comparatively
- well during this period.

## .

- Abbreviated
- dynamical
- coupled
- models

- Blue asterisk *
- means the model
- did comparatively
- well during this period.

## .

- *

- *

- Fully comprehensive
- coupled models:
- Run in the U.S.

- Blue asterisk *
- means the model
- did comparatively
- well during this period.

## .

- *

- *

- *

- Fully comprehensive
- coupled models:
- Run outside of U.S.

- Blue asterisk *
- means the model
- did comparatively
- well during this period.

## .

- *

- Statistical models
- based on the
- redness of the
- coupled system

- Blue asterisk *
- means the model
- did comparatively
- well during this period.

## .

- *

- Statistical models
- based on linear
- or nonlinear
- regression

- Blue asterisk *
- means the model
- did comparatively
- well during this period.

## .

- *

- *

- Statistical models
- based on unique
- designs (regression
- to construct an analog,
- neurological network).

- Blue asterisk *
- means the model
- did comparatively
- well during this period.

## The following graphs show how each model

- did in predicting the ENSO state from JFM 2006
- to ASO 2007, by one-month increments (so there
- are up to 18 3-month periods), for lead times of 1
- to 5 months (1 month lead is really “zero lead”,
- such as a forecast for JFM made from December
- [or even earlier] initial conditions).
- Scores:
- Correlation (uncentered; means not removed)
- RMSE Skill score: ( 1 – [RMSEmodel/RMSEclim] )
- The blue curve shows the model skill.
- The pink curve shows the skill of persistence from
-         the most recently observed one month SST.

## (blue line)

- persistence

## *

- (blue line)

- persistence

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- persistence

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- persistence

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- persistence

## *

- (blue line)

- persistence

## *

- (blue line)

- persistence

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- persistence

## *

- (blue line)

- persistence

## *

- (blue line)

- persistence

## *

- (blue line)

- persistence

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- persistence

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- persistence

## *

- (blue line)

- persistence

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- persistence

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- persistence

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- persistence

## *

- (blue line)

- persistence

## *

- (blue line)

- persistence

## *

- (blue line)

- persistence

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- persistence

## (blue line)

- persistence

## (blue line)

- persistence

## ----------------     -----------------   -----------

- ----------------     -----------------   **-----------**

- ----------------     -----------------   **-----------**

## End of 2005: CPC and IRI statements about La Niña

- ...current conditions stronger-than-average easterly winds over the central equatorial Pacific) and recent observed trends (decreas-ing SST anomalies throughout the central and eastern equatorial Pacific) do not support the development of El Niño. Rather, they support either a continuation of ENSO-neutral conditions or the development of weak La Niña conditions during the next 6-9 months.

**CPC**, early October:
- ....current conditions and recent observed trends support a  cont-inuation of ENSO-neutral cond-itions for the next 3-6 months.

**IRI**, mid-October: The likeli-hood of maintaining neutral conditions is at least 95% through the end of 2005. The probability of a La Niña dev-eloping between now and the end of 2005 is approxi-mately 1%.

**IRI**, mid-November: The likeli-hood of maintaining neutral conditions is virtually certain through the end of 2005. The probability of a La Niña devel-oping between now and the end of 2005 is less than 1%.

## End of 2005: CPC and IRI statements about La Niña

- ...current conditions (stronger-than-average easterly winds over the central equatorial Pacific) and recent observed trends (decreasing SST
- anomalies throughout the central and eastern equatorial Pacific) do not support the development of El Niño. Rather, they support either a continuation of ENSO-neutral conditions or the development of weak La Niña conditions.

**IRI**, mid-December: ...the probab-ility of a La Niña developing over the next season is approximately 10%, increasing to about 20% by mid-2006. The chances for developing El Niño conditions are estimated at less than 1% through March 2006, increasing to approx-imately 20% by mid-2006. The likelihood of maintaining neutral conditions remains very high through early 2006.

## Middle to Late 2006: CPC and IRI statements about El Niño

**CPC**, early September:
- Synopsis: ENSO-neutral conditions are expected to continue for the next one to two months, with weak warm episode (El Niño) conditions likely by the end of 2006.

**CPC**, early August:
- Synopsis: ENSO-neutral conditions are expected to continue for the next one to three months, with a 50% chance that weak El Niño conditions will develop by the end of 2006.

**IRI**, mid-August: The likeli-hood of maintaining neutral conditions is at 60% through the end of 2006, and the probability of an El Niño dev-eloping between now and the end of 2006 is approxi-mately 35 to 40%.

**IRI**, mid-September: The likeli-hood of maintaining neutral conditions through the end of 2006 is about 40%. The probability of an El Niño devel-oping between now and the end of 2005 is approximately 60%. Likely El Niño strength would be weak.

## Middle to Late 2006: CPC and IRI statements about El Niño

- Synopsis: El Niño coniditions are likely to continue into early 2007.
- Collectively, [these] conditions are consistent with the early stages of El Niño in the tropical Pacific.

**IRI**, mid-October: ...the probab-ility of continuing El Niño condi-tions over the next season is approximately 80%. The likelihood of neutral conditions is just under 20%. Likely strength of El Niño is
- weak to moderate.

- CPC did slightly better, on average, with these two somewhat
- unusual ENSO developments than IRI. But CPC usually
- does not usually quantify its ENSO forecasts probabilistically.

## Conclusion

- In the middle of the 2000-2009 decade, we still have **weak to**
**fair skill** in predicting the onset of non-neutral ENSO conditions
- during the early half the calendar year. In “new” situations
- (e.g. Dec. 2005, or autumn 2006), we receive surprises even at
- times of the year when we thought we had high confidence.
- Often, we predict non-neutral ENSO developments once we
*observe signs* of the emergence of an event in the middle part
- of the calendar year. Sub-surface sea temperature anomalies
- may sometimes precede SST anomalies by a month or more.
- Once an event begins, we are skillful at predicting its evolution
- and are helpful to users whose season of climate effects is later.
- If climate change is causing different relative relationships with-
- in the new normal ranges, then statistical models may fail us.
- We are MUCH better than we were 20 years ago. To the layman,
- however, our ENSO predictive skill likely still looks weak to fair.