# Presentation: 506429

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

**Update prepared by**
**Climate Prediction Center / NCEP**
**   ****March 14, 2005**

## Outline

** ****Overview**
** ****Recent Evolution and Current Conditions**
** ****Oceanic Ni********o Index (ONI) – “Revised 1 March 2004”**
** ****Pacific SST Outlook**
** ****U.S. Seasonal Precipitation and  **
**  ****Temperature Outlooks**
** ****Summary**

## Overview

** ****The pattern of warmth in the equatorial Pacific indicates that a weak mid-Pacific warm episode (El Ni****ñ****o) has been in progress since August 2004. **
** ****Since the beginning of January 2005 SST departures have decreased throughout the eastern equatorial Pacific, while departures greater than +1C persisted in the west-central equatorial Pacific (165E—170W).**
** ****Since early February precipitation has been more persistent over the anomalously warm west-central equatorial Pacific, accompanied by low-level westerly wind anomalies.**
** ****A strong eastward-propagating oceanic Kelvin wave has developed and is expected to warm the eastern equatorial Pacific during the next several weeks.**
** ****The most recent value of the ONI  is +0.6 (for the period December 2004 -February 2005) and t****he most recent 5-month running mean value (October 2004-February 2005) of the Southern Oscillation Index (SOI) is –1.2.  Both are consistent in indicating continued warm episode conditions.**
** ****Based on statistical and coupled model forecasts and recent trends in SST anomalies it seems most likely that the warm episode will continue to fade and that ENSO-neutral conditions will prevail during the late northern spring and summer of 2005.****  **

## Recent Evolution of Equatorial Pacific SST Departures 

**Recent Evolution of Equatorial Pacific SST Departures**** **

**Longitude**

**Time**

- Departures increased substantially in the central equatorial Pacific during July 2004.
-  The warmth in the central equatorial Pacific expanded eastward during July-October 2004.
-  The warmth in the equatorial Pacific persisted during November-December 2004.
- Recently, cooling has occurred  east of the date line.

## Niño Indices: Recent Evolution

**SST anomalies greater than or equal to +0.5C are restricted to the Ni****ño 4 region. Since January 2005, departures have decreased in all of the Niño regions. **

## Average SST Departures in the Tropical Pacific: Last 4 Weeks

- Equatorial ocean surface temperatures greater than +0.5°C (~1°F) above average are found between 150°E and 160°W. Departures greater than +1°C are found between 165°E and 170°W. Negative SST departures are found between 125°W and the South American coast.
**13 February-12 March 2005**

## Global SST Departures (Deg C): 13 Feb.-12 Mar. 2005

## Evolution of SST Departure Patterns in the Last 4 Weeks

- During mid-February through early March 2005 positive SST anomalies persisted in the central and west-central equatorial Pacific, where anomalies of greater than +1°C were observed. Farther east, departures decreased in late February, with negative values appearing in the eastern equatorial Pacific. However, SST departures increased in the last week.

## Anomalous OLR and 850-hPa Wind: last 30 days

**Anomalous OLR and 850-hPa Wind: last 30 days**

**Negative OLR anomalies (above-average rainfall) have prevailed over the central equatorial Pacific and along the South Pacific Convergence Zone during the last 30 days. Positive OLR anomalies (below-average rainfall) persisted over Indonesia and Australia**

**Low-level (850-hPa) westerly wind anomalies (m/s) have persisted over the central equatorial Pacific during the last 30 days. A series of tropical cyclones, which developed over low-latitudes in the Southern Hemisphere, affected American Samoa.**

**W m****-2**

## Upper-Ocean Conditions in the Eq. Pacific

**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 warm (El Niño) episode.**
** ****The upper ocean heat content is 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.**
** ****Note that the most recent values of anomalous upper ocean heat content and thermocline slope are less in magnitude than those observed in recent warm episodes (e.g., 1991-92, 1993, 1994-95, 1997-98 and 2002-03).**

**Cold Episodes**

**Warm Episodes**

**Themocline slope index is the difference in the anomalous depth of the 20C isotherm  between the western Pacific (160E-150W) and the eastern Pacific (90-140W).**

## Subsurface Conditions in the Eq. Pacific

**Subsurface Conditions**** ****in the Eq. Pacific**

** ****During January-February 2005 the basin-wide upper-ocean heat content remained slightly greater than average. The recent increase in subsurface temperature departures in the central equatorial Pacific indicates the development of a new oceanic Kelvin wave, which is consistent with the westerly wind anomalies in that region.**

**Time**

**Longitude**

## Intraseasonal Variability

**MJO activity during June-October and December 2004-January 2005 resulted in significant variability in the atmosphere (wind and pressure) and Pacific Ocean (surface and subsurface temperature).**
**Related to this activity**
** ****significant weakening of the low-level easterly winds occurred over the equatorial Pacific during late June-early July 2004, late August-early September 2004, October 2004 and January 2005.**
**Each of these events initiated eastward-propagating oceanic Kelvin waves.**

## Heat Content Evolution in the Eq. Pacific

**Heat Content Evolution**** ****in the Eq. Pacific**

** ****During the last year there were several cases of eastward-propagating oceanic Kelvin waves (indicated by dashed black lines in the figure).**
** ****Each Kelvin wave was initiated when the easterlies weakened over the equatorial Pacific.**
** ****Between August 2004 and January 2005 Kelvin wave activity weakened and the average heat content (0-300 m) decreased.**
** ****However, during February 2005 a stronger Kelvin wave developed.**

**Time**

**Longitude**

## 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**

**Weaker-than-average easterlies (orange/red shading). **
**Stronger-than-average easterlies (blue shading).**

**Westerly anomalies, which developed over the western equatorial Pacific in early January, expanded eastward through the end of the January and persisted through early March.**
**Also,westerly anomalies developed over the eastern equatorial Pacific.**

## 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**

**The eastward propagation of the positive/negative anomaly dipole over the Indian Ocean and Indonesia (late December 2004-early January 2005) was associated with the MJO. Recently, enhanced convection has become persistent in the region of the anomalously warm water near the date line.**

## 200-hPa Velocity Potential Anomalies

**200-hPa Velocity Potential Anomalies**

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

**Positive anomalies (orange/red shading) indicate unfavorable conditions for precipitation.**

**Longitude**

**Time**

**The eastward propagation of negative anomalies over the Indian ocean and positive anomalies over Indonesia and the Pacific during December/early January was associated with the MJO. Recently, a more stationary pattern has developed, which is consistent with the positive SST departures in the central eq. Pacific.**

## Oceanic Niño Index (ONI)

**Based on the principal measure for monitoring, assessment, and prediction of ENSO (SST departures from average in the Niño 3.4 region)**
**Three-month running-mean values of SST departures from average in the**** ****Niño 3.4 region, based on a set of improved homogeneous historical SST analyses (Extended Reconstructed SST – ERSST.v2). The methodology is described in Smith and Reynolds, 2003, *****J. Climate*****, 16, 1495-1510.**
**Used to place current conditions in historical perspective**
**NOAA operational definitions of El Niño and La Niña are keyed to the 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 Ni**__****__**a:**_** characterized by a *****negative***** ONI less than or equal to ********0.5°C.**
**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 months.**

## ONI: Evolution since 1950

**ONI: Evolution since 1950**

**The most recent ONI value (+0.6C for December 2004-February 2005) exceeds the threshold (+0.5C) for El Ni****ño ****conditions****. **

**El Ni****ñ****o**

**La Ni****ña**

**neutral**

## Historical El Niño and La Niña episodes, based on the ONI computed using ERSST.v2

| Warm Episodes   max | Cold Episodes      min |
| --- | --- |
| JAS 1951 - NDJ 1951/52                0.7
MAM 1957 – MJJ 1958                 1.6         | ASO 1949 – FMA 1951              -1.8
MAM 1954 – DJF 1956/57         -2.1 |
| JJA 1963 – DJF 1963/64                1.0 | ASO 1961 – MAM 1962             -0.6 |
| MJJ 1965 – MAM 1966                 1.6 | MAM 1964 – JFM 1965             -1.1 |
| OND 1968 – AMJ 1969                 1.0 | SON 1967 – MAM 1968             -0.9 |
| ASO 1969 – DJF 1969/70              0.7 | JJA 1970 – DJF 1971/72             -1.4 |
| AMJ 1972 – FMA 1973                 2.1 | AMJ 1973 – JJA 1974                 -2.0 |
| ASO 1976 – JFM 1977                  0.8 | ASO 1974 – AMJ 1976               -1.8 |
| ASO 1977 - DJF 1977/78               0.8 | ASO 1983 – DJF 1983/84           -0.9 |
| AMJ 1982 – MJJ 1983                  2.3 | SON 1984 – MJJ 1985                -1.1 |
| JAS 1986 – JFM 1988                    1.6 | AMJ 1988 – AMJ 1989               -1.9 |
| AMJ 1991 – MJJ 1992                  1.8 | ASO 1995 – FMA 1996               -0.8 |
| FMA 1993 – JJA 1993                   0.8 | JJA 1998 – MJJ 2000                 -1.6 |
| MAM 1994 – FMA 1995               1.3 | SON 2000 – JFM 2001                -0.7 |
| AMJ 1997 – MAM 1998                2.5
AMJ 2002 – FMA 2003                 1.5 | 
 |

## Warm (red) and cold (blue) episodes based on a threshold of +/- 0.5 C for the Oceanic Nino Index (ONI) [3 month running mean of ERSST.v2 SST anomalies in the Nino 3.4 region (5N-5S, 120-170W)], based on the 1971-2000 base period. For historical purposes cold and warm episodes (blue and red colored numbers) are defined when the threshold is met for a minimum of 5 consecutive over-lapping seasons.

## Warm (red) and cold (blue) episodes based on a threshold of +/- 0.5 C for the Oceanic Nino Index (ONI) [3 month running mean of ERSST.v2 SST anomalies in the Nino 3.4 region (5N-5S, 120-170W)], based on the 1971-2000 base period. For historical purposes cold and warm episodes (blue and red colored numbers) are defined when the threshold is met for a minimum of 5 consecutive over-lapping seasons.

## Warm (red) and cold (blue) episodes based on a threshold of +/- 0.5 C for the Oceanic Nino Index (ONI) [3 month running mean of ERSST.v2 SST anomalies in the Nino 3.4 region (5N-5S, 120-170W)], based on the 1971-2000 base period. For historical purposes cold and warm episodes (blue and red colored numbers) are defined when the threshold is met for a minimum of 5 consecutive over-lapping seasons.

- 0.5

- 0.4

- 0.2

- 0.2

- 0.2

- 0.3

-    0.4

-  **0.7**

**0.8**

**0.9**

**0.9**

**0.9**

**0.8**

**0.6**

## Niño 3.4 evolution – El Niño episodes

**Most recent Ni****ño**** 3.4 values (heavy black line) compared to values for 13 historical El Ni****ño episodes. On the time axis year 0001 is the first year of a warm episode.**

**Recent Ni****ño 3.4 ****values, derived from ERSST.v2, lie in the lower portion of the distribution of historical El Ni****ño episodes since 1950.**

## Niño 4 evolution – El Niño episodes

**Most recent Ni****ño**** 4 values (heavy black line) compared to values for 13 historical El Ni****ño episodes. On the time axis year 0001 is the first year of a warm episode.**

**Recent Ni****ño 4 ****values, derived from ERSST.v2, lie near the top of the distribution of historical El Ni****ño episodes since 1950.**

## Niño 3 evolution – El Niño episodes

**Most recent Ni****ño**** 3 values (heavy black line) compared to values for 13 historical El Ni****ño episodes. On the time axis year 0001 is the first year of a warm episode.**

**Recent Ni****ño 3 ****values, derived from ERSST.v2, lie at the bottom of the distribution of historical El Ni****ño episodes since 1950.**

## Niño 1+2 evolution – El Niño episodes

**Most recent Ni****ño**** 1+2 values (heavy black line) compared to values for 13 historical El Ni****ño episodes. On the time axis year 0001 is the first year of a warm episode.**

**Recent Ni****ño 1+2 ****values, derived from ERSST.v2, lie near the bottom of the distribution of historical El Ni****ño episodes since 1950. NOTE: there can be large differences between the operational Niño 1+2 values and those shown here, due to uncertainties in the reconstructed SST analyses.**

## Pacific Niño 3.4 SST Outlook

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

- Figure provided by the International Research Institute (IRI) for Climate Prediction (updated 17 February 2005).

## SST Outlook: NCEP CFS 23 February 2005

- A gradual decrease in SST anomalies over the next six to nine months is indicated by the CFS mean (blue line).

## U. S. Seasonal OutlooksMarch-May 2005

**Temperature**

**Precipitation**

**Outlooks combine ****long-term trends**** ****and**** ****soil-moisture effects, with**** typical ****ENSO cycle impacts, when appropriate.**

## Summary

** ****The pattern of warmth in the equatorial Pacific indicates that a weak mid-Pacific warm episode (El Ni****ñ****o) has been in progress since August 2004. **
** ****Since the beginning of January 2005 SST departures have decreased throughout the eastern equatorial Pacific, while departures greater than +1C persisted in the west-central equatorial Pacific (165E—170W).**
** ****Since early February precipitation has been more persistent over the anomalously warm west-central equatorial Pacific, accompanied by low-level westerly wind anomalies.**
** ****A strong eastward-propagating oceanic Kelvin wave has developed and is expected to warm the eastern equatorial Pacific during the next several weeks.**
** ****The most recent value of the ONI  is +0.6 (for the period December 2004 -February 2005) and t****he most recent 5-month running mean value (October 2004-February 2005) of the Southern Oscillation Index (SOI) is –1.2.  Both are consistent in indicating continued warm episode conditions.**
** ****Based on statistical and coupled model forecasts and recent trends in SST anomalies it seems most likely that the warm episode will continue to fade and that ENSO-neutral conditions will prevail during the late northern spring and summer of 2005.****  **