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ENSO Cycle: RecentEvolution, Current
Status and Predictions
Update prepared by
Climate Prediction Center / NCEP
May 30, 2006
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Outline
Overview
Recent Evolution and Current Conditions
Oceanic Nio Index (ONI) Revised 1 March 2004
Pacific SST Outlook
U.S. Seasonal Precipitation andTemperature Outlooks
Summary
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Overview
The recent patterns of SST and upper-ocean heat content indicate a returnto near-average (ENSO-neutral) conditions in the tropical Pacific Ocean.
Statistical and coupled model forecasts indicate that ENSO-neutral
conditions are likely for the remainder of 2006.
Thus, ENSO-neutral conditions can be expected during the next 3-6
months.
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Recent Evolution of Equatorial
Pacific SST Departures
Longitude
Time
During September 2005- January 2006
SST anomalies decreased and below-
average temperatures developed
throughout most of the central and
eastern equatorial Pacific.
In February 2006 positive SST
anomalies developed in the extreme
eastern equatorial Pacific, similar to
what occurred in 1999, 2000 and 2001
(La Nia years).
Recently, near average SSTs have been
observed throughout the equatorial
Pacific, except for 90-100W where
negative anomalies were observed and
for the region west of 180 where
positive anomalies greater than 0.5Cwere observed.
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Nio Indices: Recent Evolution
The latest weekly SST anomalies are
slightly positive in the Nio 4 and 3.4
regions, near zero in the Nio 3 region,and negative in the Nio 1+2 region.
The weak anomalies in all regions
indicate ENSO neutral conditions.
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Average SST Departures in the
Tropical Pacific: Last 4 WeeksEquatorial ocean surface temperatures were near average at most locations across the
equatorial Pacific, except for areas close to the South American coast where negative
anomalies are observed.
30 April 27 May 2006
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Global SST Departures (Deg C):
30 Apr-27 May 2006
The subtropical Atlantic basin (5-25N) has been warmer than average for more than a
year. The equatorial Indian Ocean SSTs are above average. Positive anomalies
dominate the high latitudes in the North Atlantic Ocean and the subtropical and lower
mid-latitudes of the central Indian, South Pacific and western South Atlantic Oceans.
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Evolution of SST Departure
Patterns in the Last 4 Weeks
During May 2006 basin-wide conditions were nearaverage. Negative anomalies were observed in theextreme eastern equatorial Pacific near the South
American coast.
Over this 4-week period warming was observed in
most of the equatorial Pacific.
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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 Nio)
episode.
The upper ocean heat content is
least prior to and during the early
stages of a cold (La Nia) episode.
The slope of the oceanicthermocline is least (greatest) during
warm (cold) episodes.
The most recent values of the
upper-ocean heat anomalies and the
thermocline slope index are near
zero, indicating near average
conditions in the equatorial Pacific.
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).
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Central & Eastern Pacific Upper-Ocean
Heat Content Anomalies
Decreasing upper-ocean heat content was observed during July 2005 through
January 2006. Since early February, upper ocean heat content has increased andis currently slightly positive.
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Subsurface Conditions in the
Eq. Pacific
Time
During March early May 2006 positivesubsurface temperature anomalies spread
eastward, while the area of negative
anomalies became restricted to the extreme
eastern equatorial Pacific.
The most recent analysis shows negative
anomalies in the far eastern equatorial
Pacific and positive anomalies between 50and 250 m depth in the region to the west
of 100W.
LongitudeMost recent pentad analysis
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Tropical OLR and winds: last 30 days
Negative OLR anomalies (enhanced convection and precipitation,
blue shading) were observed over portions of Indonesia and
northern Australia. Positive OLR anomalies (suppressed
convection and precipitation, orange shading) were observed overthe central and eastern equatorial Pacific.
Near-average low-level winds were observed over the equatorial
Pacific.
The patterns of anomalous OLR and wind during the last 30 days have weakened
considerably during the last month, but still continue to reflect weak La Nia conditions.Atmospheric conditions over the tropical Pacific often lag changes in the ocean state.
Weak cyclonic circulation anomalies (indicated by C in the figure)
were observed north and south of the equator over the central
tropical Pacific.
C
C
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US Temperature and Precipitation Patterns
during the last 30 and 90 days
30-day (ending 29 May 2006) % of
average precipitation
30-day (ending 27 May 2006)
temperature departures (degree C)
90-day (ending 29 May 2006) % of
average precipitation
90-day (ending 27 May 2006)
temperature departures (degree C)
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Intraseasonal Variability
Intraseasonal variability in the atmosphere (wind
and pressure), often related to the Madden-Julian
Oscillation (MJO), can have a significant impacton surface and subsurface conditions in the Pacific
Ocean.
Related to this activity
significant weakening of the low-level easterlywinds usually initiates an eastward-propagating
oceanic Kelvin wave.
Several Kelvin waves have occurred during thelast year (see next slide).
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Heat Content Evolution in the
Eq. Pacific
The upper-ocean heat content gradually
decreased in the eastern and centralequatorial Pacific and increased in the
extreme western equatorial Pacific
during mid-2005. as a precursor to weak
La Nia conditions that developed in late
2005.
During March-April 2006 the upper-
ocean heat content increased as La Nia
conditions weakened and ENSO-neutral
conditions became established.
Time
Longitude
The downwelling (upwelling) phase of
Kelvin waves is indicated by the dashed
(dotted) lines. Downwelling (upwelling)
produces an increase (decrease) in upper-ocean heat content.
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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).
Low-level easterly wind
anomalies dominated the
central equatorial Pacific
during October 2005 April
2006.
Recently, low-level easterly
winds have again become
stronger than average over the
equatorial central Pacific.
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200-hPa Velocity Potential
Anomalies (5N-5S)
Negative anomalies (green shading)
indicate favorable conditions for
precipitation.
Positive anomalies (brown shading)
indicate unfavorable conditions for
precipitation.
Longitude
Time From late December to late February,there was some eastward propagation,
indicating weak-to-moderate MJO
activity.
In early March the MJO activity
weakened and became incoherent.
Signs of strengthening MJO activity are
evident in May 2006.
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Outgoing Longwave Radiation
(OLR) Anomalies
Wetter-than-averageconditions (blue shading)
Drier-than-average conditions
(orange/red shading)
Longitude
Time
From November 2005 through
April 2006 a persistent pattern of
suppressed convection was
observed near the date line(180W), while enhanced
convection, modulated by weak
MJO activity, was observed over
Indonesia (120-130E).
The overall pattern of anomalousconvection during this period is
consistent with La Nia conditions
in the tropical Pacific.
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Oceanic Nio Index (ONI) Based on the principal measure for monitoring, assessment,
and prediction of ENSO (SST departures from average in
the Nio 3.4 region)
Three-month running-mean values of SST departures from
average in the Nio 3.4 region, based on a set of improved
homogeneous historical SST analyses (ExtendedReconstructed 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 Nio and La Nia are
keyed to the index.
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NOAA Operational Definitionsfor El Nio and La Nia
El Nio: characterized by apositive ONI greater than orequal to +0.5C.
La Nia: characterized by anegative ONI less than or
equal to -0.5C.
To be classified as a full-fledged El Nio or La Nia
episode these thresholds must be exceeded for a period of
at least 5 consecutive months.
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ONI: Evolution since 1950
The most recent ONI
value (February-April
2006) is -0.4C.
El Nio
La Nia
neutral
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Historical El Nio and La Nia episodes,
based on the ONI computed using ERSST.v2
AMJ 1997 MAM 1998 2.5
AMJ 2002 FMA 2003 1.5
JJA 2004 JFM 2005 0.9
SON 2000 JFM 2001 -0.7MAM 1994 FMA 1995 1.3
JJA 1998 MJJ 2000 -1.6FMA 1993 JJA 1993 0.8
ASO 1995 FMA 1996 -0.8AMJ 1991 MJJ 1992 1.8
AMJ 1988 AMJ 1989 -1.9JAS 1986 JFM 1988 1.6
SON 1984 MJJ 1985 -1.1AMJ 1982 MJJ 1983 2.3
ASO 1983 DJF 1983/84 -0.9ASO 1977 - DJF 1977/78 0.8
ASO 1974 AMJ 1976 -1.8ASO 1976 JFM 1977 0.8
AMJ 1973 JJA 1974 -2.0AMJ 1972 FMA 1973 2.1
JJA 1970 DJF 1971/72 -1.4ASO 1969 DJF 1969/70 0.7
SON 1967 MAM 1968 -0.9OND 1968 AMJ 1969 1.0
MAM 1964 JFM 1965 -1.1MJJ 1965 MAM 1966 1.6
ASO 1961 MAM 1962 -0.6JJA 1963 DJF 1963/64 1.0
ASO 1949 FMA 1951 -1.8
MAM 1954 DJF 1956/57 -2.1
JAS 1951 - NDJ 1951/52 0.7
MAM 1957 MJJ 1958 1.6
Cold Episodes minWarm Episodes max
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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 aminimum of 5 consecutive over-lapping seasons.
Year DJF JFM FMA MAM AMJ MJJ JJA JAS ASO SON OND NDJ
1950 -1.8 -1.5 -1.4 -1.4 -1.4 -1.2 -0.9 -0.8 -0.8 -0.8 -0.9 -1.0
1951 -1.0 -0.8 -0.6 -0.4 -0.2 0.1 0.4 0.5 0.6 0.7 0.7 0.6
1952 0.3 0.1 0.1 0.1 0.0 -0.2 -0.3 -0.3 -0.1 -0.2 -0.2 -0.1
1953 0.1 0.3 0.4 0.5 0.5 0.4 0.4 0.4 0.4 0.4 0.3 0.31954 0.3 0.2 -0.1 -0.5 -0.7 -0.7 -0.8 -1.0 -1.1 -1.1 -1.0 -1.0
1955 -1.0 -0.9 -0.9 -1.0 -1.1 -1.0 -1.0 -1.0 -1.5 -1.8 -2.1 -1.7
1956 -1.2 -0.8 -0.7 -0.6 -0.6 -0.6 -0.7 -0.8 -0.9 -0.9 -0.9 -0.8
1957 -0.5 -0.1 0.2 0.6 0.7 0.8 0.9 0.9 0.8 0.9 1.2 1.5
1958 1.6 1.5 1.1 0.7 0.5 0.5 0.4 0.1 0.0 0.0 0.1 0.3
1959 0.4 0.4 0.3 0.2 0.0 -0.3 -0.4 -0.5 -0.4 -0.4 -0.3 -0.3
1960 -0.3 -0.3 -0.3 -0.2 -0.1 -0.1 0.0 0.0 -0.1 -0.2 -0.3 -0.21961 -0.2 -0.2 -0.2 -0.1 0.1 0.1 0.0 -0.3 -0.6 -0.6 -0.5 -0.5
1962 -0.5 -0.5 -0.5 -0.5 -0.4 -0.3 -0.2 -0.3 -0.4 -0.6 -0.7 -0.7
1963 -0.6 -0.3 0.0 0.1 0.1 0.3 0.6 0.8 0.8 0.9 1.0 1.0
1964 0.8 0.4 -0.1 -0.5 -0.7 -0.7 -0.8 -0.9 -1.0 -1.1 -1.1 -1.0
1965 -0.8 -0.5 -0.3 0.0 0.2 0.6 1.0 1.2 1.4 1.5 1.6 1.5
1966 1.2 1.1 0.8 0.5 0.2 0.1 0.1 0.0 -0.2 -0.3 -0.3 -0.4
1967 -0.4 -0.5 -0.6 -0.5 -0.3 0.0 0.0 -0.2 -0.4 -0.5 -0.5 -0.6
1968 -0.7 -0.9 -0.8 -0.8 -0.4 0.0 0.3 0.3 0.2 0.4 0.6 0.9
1969 1.0 1.0 0.9 0.7 0.6 0.4 0.4 0.4 0.6 0.7 0.7 0.6
1970 0.5 0.3 0.2 0.1 -0.1 -0.4 -0.6 -0.8 -0.8 -0.8 -0.9 -1.2
1971 -1.4 -1.4 -1.2 -1.0 -0.8 -0.8 -0.8 -0.8 -0.9 -0.9 -1.0 -0.9
1972 -0.7 -0.3 0.0 0.3 0.5 0.8 1.1 1.3 1.5 1.8 2.0 2.1
1973 1.8 1.2 0.5 -0.1 -0.5 -0.8 -1.1 -1.3 -1.4 -1.7 -1.9 -2.0
1974 -1.8 -1.6 -1.2 -1.1 -0.9 -0.7 -0.5 -0.4 -0.5 -0.7 -0.8 -0.7
1975 -0.6 -0.6 -0.7 -0.8 -1.0 -1.1 -1.3 -1.4 -1.6 -1.6 -1.7 -1.8
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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 aminimum of 5 consecutive over-lapping seasons.
Year DJF JFM FMA MAM AMJ MJJ JJA JAS ASO SON OND NDJ
1976 -1.6 -1.2 -0.9 -0.7 -0.5 -0.2 0.1 0.3 0.5 0.7 0.8 0.8
1977 0.6 0.5 0.2 0.1 0.2 0.3 0.3 0.4 0.5 0.7 0.8 0.8
1978 0.7 0.4 0.0 -0.3 -0.4 -0.3 -0.4 -0.5 -0.5 -0.4 -0.2 -0.1
1979 -0.1 0.0 0.1 0.2 0.1 0.0 0.0 0.2 0.3 0.4 0.5 0.51980 0.5 0.3 0.2 0.2 0.3 0.3 0.2 0.0 -0.1 0.0 0.0 -0.1
1981 -0.3 -0.4 -0.4 -0.3 -0.3 -0.3 -0.4 -0.3 -0.2 -0.1 -0.1 -0.1
1982 0.0 0.1 0.2 0.4 0.6 0.7 0.8 1.0 1.5 1.9 2.2 2.3
1983 2.3 2.0 1.6 1.2 1.0 0.6 0.2 -0.2 -0.5 -0.8 -0.9 -0.8
1984 -0.5 -0.3 -0.2 -0.4 -0.5 -0.5 -0.3 -0.2 -0.3 -0.6 -1.0 -1.1
1985 -1.0 -0.8 -0.8 -0.8 -0.7 -0.5 -0.4 -0.4 -0.4 -0.3 -0.2 -0.3
1986 -0.4 -0.4 -0.3 -0.2 -0.1 0.0 0.2 0.5 0.7 0.9 1.1 1.2
1987 1.3 1.2 1.1 1.0 1.0 1.2 1.5 1.6 1.6 1.5 1.3 1.1
1988 0.8 0.5 0.1 -0.3 -0.8 -1.2 -1.2 -1.1 -1.3 -1.6 -1.9 -1.9
1989 -1.7 -1.5 -1.1 -0.9 -0.6 -0.4 -0.3 -0.3 -0.3 -0.3 -0.2 -0.1
1990 0.1 0.2 0.3 0.3 0.3 0.3 0.3 0.4 0.3 0.3 0.3 0.4
1991 0.5 0.4 0.4 0.4 0.6 0.8 0.9 0.9 0.8 1.0 1.4 1.7
1992 1.8 1.7 1.6 1.4 1.1 0.8 0.4 0.2 -0.1 -0.1 0.0 0.1
1993 0.3 0.4 0.6 0.8 0.8 0.7 0.5 0.4 0.4 0.3 0.2 0.2
1994 0.2 0.3 0.4 0.5 0.6 0.6 0.6 0.6 0.7 0.9 1.2 1.3
1995 1.2 0.9 0.7 0.4 0.2 0.1 0.0 -0.3 -0.5 -0.6 -0.7 -0.8
1996 -0.8 -0.7 -0.5 -0.3 -0.2 -0.2 -0.1 -0.2 -0.2 -0.2 -0.3 -0.4
1997 -0.4 -0.3 0.0 0.4 0.9 1.4 1.7 2.0 2.3 2.4 2.5 2.5
1998 2.4 2.0 1.4 1.1 0.4 -0.1 -0.8 -1.0 -1.1 -1.1 -1.3 -1.5
1999 -1.6 -1.2 -0.9 -0.7 -0.8 -0.8 -0.9 -0.9 -1.0 -1.2 -1.4 -1.62000 -1.6 -1.5 -1.1 -0.9 -0.7 -0.6 -0.4 -0.3 -0.4 -0.5 -0.7 -0.7
2001 -0.7 -0.5 -0.4 -0.2 -0.1 0.1 0.2 0.1 0.0 -0.1 -0.2 -0.2
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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 aminimum of 5 consecutive over-lapping seasons.
Year DJF JFM FMA MAM AMJ MJJ JJA JAS ASO SON OND NDJ
2002 -0.1 0.1 0.3 0.4 0.7 0.8 0.9 0.9 1.1 1.3 1.5 1.3
2003 1.1 0.8 0.6 0.1 -0.1 0.0 0.3 0.4 0.5 0.5 0.6
2004
20052006
2007
2008
2009
2010
2011
2012
2013
2014
2015
2016
2017
2018
2019
2020
2021
2022
2023
2024
20252026
2027
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 0.5 0.3 0.4 0.5 0.3 0.2 0.0 0.0 -0.2 -0.4 -0.7-0.8 -0.7 -0.4
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Most statistical and coupled model forecasts indicate ENSO-neutral
conditions through the end of 2006.
Pacific Nio 3.4 SST Outlook
Figure provided by the
International Research
Institute (IRI) forClimate and Society
(updated 17 May 2006).
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SST Outlook: NCEP CFS
29 May 2006
The CFS ensemble mean (blue line) indicates
slightly warmer-than-average conditions for theremainder of 2006.
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U. S. Seasonal Outlooks
June-August 2006
Temperature Precipitation
Outlooks combine long-term trends and soil-moisture effects,
with typical ENSO cycle impacts, when appropriate.
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Summary
The recent patterns of SST and upper-ocean heat content indicate a returnto near-average (ENSO-neutral) conditions in the tropical Pacific Ocean.
Statistical and coupled model forecasts indicate that ENSO-neutralconditions are likely for the remainder of 2006.
Thus, ENSO-neutral conditions can be expected during the next 3-6
months.