# Presentation: 174839

## ENSO Cycle: Recent Evolution, Current Status and Predictions

**Update prepared by**
**Climate Prediction Center / NCEP**
** ****9 February 2009**

## Outline

** ****Overview**
** ****Recent Evolution and Current Conditions**
** ****Oceanic Ni****ñ****o Index (ONI) – “****Revised December 2008****”**
** ****Pacific SST Outlook**
** ****U.S. Seasonal Precipitation and  **
**  ****Temperature Outlooks**
** ****Summary**

## Summary

** ****Atmospheric and oceanic conditions reflect La Niña.**
** ****Negative equatorial SST anomalies persist across the central and east-central Pacific Ocean.**
** ****Based on recent trends in the observations and model forecasts, La Niña conditions are likely to continue into Northern Hemisphere Spring 2009.  **

## Recent Evolution of Equatorial Pacific SST Departures (oC)

**Recent Evolution of Equatorial Pacific SST Departures (****o****C)**

**Longitude**

**Time**

**Negative sea surface temperature (SST) anomalies in the central and east-central equatorial Pacific Ocean have been in place since October 2008.**
**Positive SST anomalies have dissipated in the eastern Pacific Ocean.**

## Niño Region SST Departures (oC) Recent Evolution

**The latest weekly SST departures are:**
**Niño 4  ****	****	****-0.8****oC **
**Niño 3.4  ****	****-0.9****oC**
**Ni****ño 3     ****	****-0.7****oC**
**N****iño**** 1+2 ****	****-0.3oC**

## SST Departures (oC) in the Tropical Pacific During the Last 4 Weeks

**During the last 4-weeks, SSTs were at least 1°C below-average across the central and east-central equatorial Pacific Ocean.  **

## Global SST Departures (oC) 

**During the last four weeks, equatorial SSTs were below-average across the central and east-central Pacific Ocean, and above-average in the far western Pacific and eastern Atlantic Oceans.  Positive anomalies extended in a horseshoe pattern from the central North Pacific to the west-central South Pacific, and also covered much of the North Atlantic Ocean.  Negative anomalies were evident in a region extending from the west coast of North America to the Gulf of Alaska and Bering Sea. **

## Weekly SST Departures (oC) for the Last Four Weeks

** ****During the last four weeks negative SST anomalies have persisted in the central and east-central Pacific.**
** ****Small-scale changes in SST anomalies are evident in the eastern equatorial Pacific Ocean.  These are due to instability waves.**

**Weekly SST Departures (****o****C) ****for the Last Four Weeks**

## Upper-Ocean Conditions in the Eq. Pacific

**The monthly thermocline slope index represents the difference in anomalous depth of the 20****o****C isotherm between the western Pacific (160****o****E-150****o****W) and the eastern Pacific (90****o****-140****o****W).**

**Upper-Ocean Conditions in the Eq. Pacific**

-  **The basin-wide equatorial upper ocean (0-300 m) heat content is ****greatest**** prior to and during the early stages of a Pacific ****warm ****(El Niño) episode (compare top 2 panels) and ****least**** prior to and during the early stages of a ****cold**** (La Niña) episode.**
** ****The slope of the oceanic thermocline is least (greatest) during warm (cold) episodes.**
** ****Current values of the upper-ocean heat anomalies (negative) and the thermocline slope index (positive) indicate La Niña.**

**Cold Episodes**
**Warm Episodes**

## Central & Eastern Pacific Upper-Ocean        (0-300 m) Weekly Heat Content Anomalies

**The upper ocean heat content was below-average across the eastern half of the equatorial Pacific Ocean between January and April 2008 and again since  mid-August 2008.  The negative heat content anomalies have weakened since late December 2008.**

## Sub-Surface Temperature Departures (oC) in  the Equatorial Pacific

**Sub-Surface Temperature Departures (****o****C) ****in **** ****the Equatorial Pacific**

**Time**

**Longitude**

**Most recent pentad analysis**

** ****During December 2008 through January 2009, negative sub-surface temperature departures persisted in the eastern half of the Pacific, while positive departures in the western Pacific expanded eastward.  **
** ****The most recent period (below) shows negative subsurface temperature anomalies in the central and eastern Pacific, and positive anomalies continuing to shift eastward at depth.**

## Tropical OLR and Wind AnomaliesDuring the Last 30 Days

**Tropical OLR and Wind Anomalies****During the Last 30 Days**

**Positive OLR anomalies (suppressed convection and precipitation, red shading) were observed between 160****°****E and 150°W, while negative anomalies (enhanced convection, blue shading) were present over eastern Indonesia, Malaysia, the Philippines, northern Australia, and the SPCZ region.**

**Upper-level (200-hPa) westerly wind anomalies continued over much of the equatorial Pacific. An anomalous cyclonic couplet is evident in the subtropics consistent with La Ni****ñ****a.**

**Low-level (850-hPa) easterly wind anomalies persisted over the western and central tropical Pacific Ocean.**

**C**

**C**

## Atmospheric Circulation over the North Pacific & North America During the Last 60 Days

**925-hPa Temp. Anoms. (****o****C)**

**Atmospheric Circulation over the North Pacific & North America During the Last 60 Days**

**200-hPa Wind **

**In December, the atmospheric circulation featured an anomalous ridge in the North Pacific with a downstream trough centered over Canada. This trough contributed to below-average temperatures across much of Alaska and Canada.   In January, an anomalous ridge was evident near the west coast of North America and a trough was present over eastern N. America.  This resulted in below-average temperatures across the eastern United States and Canada and above-average temperatures over western N. America.  **

## U.S. Temperature and Precipitation Departures During the Last 30 and 90 Days

**U.S. Temperature and Precipitation Departures During the Last 30 and 90 Days**

**30-day (ending 7 Feb 2009) temperature departures (degree C)**

**90-day (ending 8 Feb 2009) % of average precipitation**

**90-day (ending 7 Feb 2009) temperature departures (degree C)**

**Last 30 Days**

**Last 90 Days**

**30-day (ending 8 Feb 2009) % of average precipitation**

## Intraseasonal Variability

**Intraseasonal variability in the atmosphere (wind and pressure), which is often related to the Madden-Julian Oscillation (MJO),  can significantly impact surface and subsurface conditions across the Pacific Ocean.**
**Related to this activity**
** ****significant weakening of the low-level easterly winds usually initiates an eastward-propagating oceanic Kelvin wave.**
**Several Kelvin waves have occurred during the last year (see next slide).**

## Weekly Heat Content Evolution in the Equatorial Pacific

**Oceanic Kelvin waves have alternating warm and cold phases. The warm**_** **_**phase is indicated by dashed  lines. Down-welling and warming occur in the leading portion of a Kelvin wave, and up-welling and cooling occur in the trailing portion. **

**Weekly Heat Content Evolution**** ****in the Equatorial Pacific**

**Time**

**Longitude**

**  ****During January - July 2008, subsurface temperature anomalies across the central and eastern equatorial Pacific increased consistent with the transition from La Niña to ENSO-neutral conditions.  **
** ****The upper-ocean heat content was occasionally affected by weak oceanic Kelvin wave activity during the period (dashed lines).**
** ****From September 2008 – January 2009, negative heat content anomalies strengthened in the central and eastern equatorial Pacific, as La Niña conditions redeveloped.**
** ****Recently, positive subsurface temperature anomalies have expanded into the central Pacific Ocean.   **

## Low-level (850-hPa) Zonal (east-west) Wind Anomalies (m s-1)

**Low-level (850-hPa) Zonal (east-west) ****Wind Anomalies (m s****-1****)**

**Longitude**

**Time**

**Westerly wind anomalies (orange/red shading). **
**Easterly wind anomalies (blue shading).**

**Low-level (850-hPa) easterly wind anomalies have persisted since January 2007 over the equatorial Pacific between 150oE and 150oW. **
**However, in late September- early October 2008, intraseasonal (MJO) activity briefly weakened the easterly anomalies across the central equatorial Pacific (dashed red oval in figure). **
**Since early October, strong easterly anomalies have dominated the central equatorial Pacific.**

## 200-hPa Velocity Potential Anomalies (5oN-5oS)

**200-hPa Velocity Potential ****Anomalies (5****o****N-5****o****S)**

**Negative anomalies (green shading) indicate favorable conditions for precipitation.**

**Positive anomalies (brown shading) indicate unfavorable conditions for precipitation.**

**Longitude**

**Time**

**Positive velocity potential anomalies (associated with suppressed convection) have been dominant near the Date Line.**

**The MJO was active in September and October 2008.**
**Since mid-January, the MJO has been active.**

## Outgoing Longwave Radiation (OLR) Anomalies

**Outgoing Longwave Radiation (OLR) Anomalies**

**Wetter-than-average conditions (blue shading)**

**Drier-than-average conditions (orange/red shading)**

**Longitude**

**Time**

**Since February 2007, convection has been suppressed across the central equatorial Pacific Ocean.**
**Convection has occasionally been enhanced over the western equatorial Pacific and central Indian Ocean.  Since November 2008, convection has become more persistent over Indonesia. **

## Oceanic Niño Index (ONI)

**The ONI is based on SST departures from average in the Niño 3.4 region, and is a principal measure for monitoring, assessing, and predicting ENSO.**
_**Defined as the three-month running-mean SST departures in the Niño 3.4 region**_**. Departures are based on a set of improved homogeneous historical SST analyses (Extended Reconstructed SST – ****ERSST.v3b****). The SST reconstruction methodology is described in Smith et al., 2008, *****J. Climate, *****vol. 21, 2283-2296.)**
**Used to place current events into a historical perspective**
**NOAA’s operational definitions of El Niño and La Niña are keyed to the ONI index****.**

## NOAA Operational Definitions for El Niño and La Niña

_**El Niño:**_** characterized by a *****positive*****  ONI greater than or equal to +0.5°C.**
_**La Niña:**_** characterized by a *****negative***** ONI less than or equal to ****-****0.5°C.**
**By historical standards, to be classified as a full-fledged El ****Ni****ño or La ****Ni****ña **_**episode,**_** these thresholds must be exceeded for a period of at least 5 consecutive overlapping 3-month seasons.  **
***CPC considers ******El Niño or La Niña ***_***conditions***_*** to occur when the monthly Niño3.4 SST departures meet or exceed +/- 0.5°C along with consistent atmospheric features.  These anomalies must also be forecasted to persist for 3 consecutive months.  ***

## ONI (oC): Evolution since 1950

**ONI (****o****C): Evolution since 1950**

**The most recent ONI value (November 2008–January 2009) is ****−****0.6****o****C.**

**El Ni****ñ****o**

**La Ni****ña**

**neutral**

## Historical El Niño and La Niña Episodes Based on the ONI computed using ERSST.v3b

**NOTE: **
**After updating the ocean analysis to ERSST.v3b, a new La Ni****ñ****a episode was classified (ASO 1962- DJF 1962/63) and two previous La Niña episodes were combined into one single episode (AMJ 1973- MAM 1976).**

|                                        Highest
El Niño                   ONI Value |                                   Lowest
La Nina             ONI Value |
| --- | --- |
| JAS 1951 - NDJ 1951/52                     0.8 | ASO 1949 – FMA 1951                     -1.7 |
| MAM 1957 – MJJ 1958                      1.7 | MAM 1954 – DJF 1956/57                -2.1 |
| JJA 1963 – DJF 1963/64                     1.0 | ASO 1962 − DJF 1962/63                  -0.8 |
| MJJ 1965 – MAM 1966                      1.6 | MAM 1964 – DJF 1964/65                -1.1 |
| OND 1968 – MJJ 1969                        1.0 | NDJ 1967/68 – MAM 1968               -0.9 |
| ASO 1969 – DJF 1969/70                    0.8 | JJA 1970 – DJF 1971/72                   -1.3 |
| AMJ 1972 – FMA 1973                       2.1 | AMJ 1973 – MAM 1976                   -2.0 |
| ASO 1976 – JFM 1977                        0.8 | SON 1984 – ASO 1985                      -1.0 |
| ASO 1977 - DJF 1977/78                     0.8 | AMJ 1988 – AMJ 1989                     -1.9 |
| AMJ 1982 – MJJ 1983                        2.3 | ASO 1995 – FMA 1996                     -0.7 |
| JAS 1986 – JFM 1988                         1.6 | JJA 1998 – MJJ 2000                       -1.6 |
| AMJ 1991 – JJA 1992                         1.8 | SON 2000 – JFM 2001                     -0.7 |
| AMJ 1994 – FMA 1995                       1.3 | ASO 2007 – AMJ 2008                     -1.4 |
| AMJ 1997 – AMJ 1998                       2.5 |  |
| AMJ 2002 – FMA 2003                       1.5 |  |
| MJJ 2004 – JFM 2005                        0.9 |  |
| JAS 2006 - DJF 2006/07                      1.1 | 
 |

## Historical Pacific warm (red) and cold (blue) episodes based on a threshold of +/- 0.5 oC for the Oceanic Nino Index (ONI) [3 month running mean of ERSST.v3b SST anomalies in the Nino 3.4 region (5N-5S, 120-170W)], calculated with respect to the 1971-2000 base period. For historical purposes El Niño and La Niña episodes are defined when the threshold is met for a minimum of 5 consecutive over-lapping seasons.

## Historical Pacific warm (red) and cold (blue) episodes based on a threshold of +/- 0.5 oC for the Oceanic Nino Index (ONI) [3 month running mean of ERSST.v3b SST anomalies in the Nino 3.4 region (5N-5S, 120-170W)], calculated with respect to the 1971-2000 base period. For historical purposes El Niño and La Niña episodes are defined when the threshold is met for a minimum of 5 consecutive over-lapping seasons.

## Historical Pacific warm (red) and cold (blue) episodes based on a threshold of +/- 0.5 oC for the Oceanic Nino Index (ONI) [3 month running mean of ERSST.v3b SST anomalies in the Nino 3.4 region (5N-5S, 120-170W)], calculated with respect to the 1971-2000 base period. For historical purposes El Niño and La Niña episodes are defined when the threshold is met for a minimum of 5 consecutive over-lapping seasons.

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## Pacific Niño 3.4 SST Outlook

**Pacific Ni****ño 3.4 ****SST Outlook**

- Figure provided by the International Research Institute (IRI) for Climate and Society (updated 17 January 2009).

## SST Outlook: NCEP CFS Forecast Issued 8 February 2009

**The CFS ensemble mean (heavy blue line) indicates ****La Niña conditions into Spring 2009.**

## U. S. Seasonal OutlooksFebruary – April 2009

**Temperature**

**Precipitation**

**These seasonal outlooks combine ****long-term trends and some aspects of La Niña.**

## Summary

** ****Atmospheric and oceanic conditions reflect La Niña.**
** ****Negative equatorial SST anomalies persist across the central and east-central Pacific Ocean.**
** ****Based on recent trends in the observations and model forecasts, La Niña conditions are likely to continue into Northern Hemisphere Spring 2009.  **