ENSO Cycle: Recent Evolution, Current Status and Predictions

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ENSO Cycle Recent Evolution, Current Status and
Predictions
Vernon E. Kousky And R. Wayne Higgins NOAA
Climate Prediction Center 16 October 2003
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Outline

• Overview
• The 2002-2003 Warm Episode
• Recent Evolution and Current Conditions
• Pacific SST Outlook
• Summary

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Overview

• The 2002-2003 El Niño ended during March-April
  2003, as sea surface temperatures rapidly cooled
  across the central and eastern equatorial
  Pacific.
• Cooler-than-average surface and subsurface water
  temperatures developed in the east-central and
  eastern equatorial Pacific during late NH winter
  2002-03 and continued during NH spring 2003.
• The cooling trend reversed in late May-early
  June 2003.
• By early October 2003 conditions in the central
  equatorial Pacific were slightly warmer than
  average (but still ENSO-neutral).
• Recent observed trends indicate that El Niño
  conditions might develop before the end of 2003.
• Most statistical and coupled model forecasts
  indicate near-average conditions in the tropical
  Pacific through NH winter 2003-2004, although
  some indicate that weak El Niño conditions will
  develop by winter 2003-04.

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Evolution of Equatorial Pacific SST Departures
2002-2003

• Cooling trend continued during April-May 2003.
• SST departures warmed across the eastern
  equatorial Pacific during June and July 2003,
  reducing the chances of La Niña.
• During September 2003 positive SST departures
  increased in the central and eastern equatorial
  Pacific.

• El Niño conditions occurred between June 2002 and
  March 2003.
• Rapid weakening of SST departures occurred during
  January-March 2003.

Time
Longitude
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U850, OLRa, Niño 4
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The 2002-03 El Niño Historical Perspective
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Seasonal SST Anomaly Patterns
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Seasonal Precipitation Anomaly Patterns
mm/d
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Seasonal 200-hPa Height Anomaly Patterns
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NH Monthly 500-hPa Height Anomaly Patterns
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Niño Indices Recent Evolution
SSTs increased to 0.5C or more above average in
the equatorial Pacific (Niño 4, Niño 3.4 and Niño
3 regions) by early October 2003.
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SST Anomaly Difference May to September 2003
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Average SST Departures in the Tropical Pacific
Last 4 Weeks
Equatorial ocean surface temperatures greater
than 0.5C (1F) above average are found in the
region between 110W and 150E. 14 September-11
October 2003
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Evolution of SST Departure Patterns in the Last 4
Weeks
During September 2003 positive SST anomalies
(departures from average) persisted along the
equator just west of the date line and increased
between the date line and the South American
coast. Basin-wide conditions in early October
were slightly warmer than average (borderline
ENSO-neutral and El Niño).
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Recent Evolution of Subsurface Conditions in the
Eq. Pacific

• near average conditions persisted in the eastern
  Pacific during September 2003.
• Positive anomalies persisted in the central
  equatorial Pacific at 150-200 m depth.
• During September the basin-wide upper ocean heat
  content was slightly greater than average.

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NCEP Coupled Model SST Forecasts
The NCEP coupled model indicates a gradual
warming and development of weak El Niño
conditions in the eastern equatorial Pacific
during the next 6-9 months.
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NCEP Consolidated Niño 3.4 Forecast
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Niño 3.4 SST Anomaly Forecasts

• Most statistical and coupled model forecasts
  indicate near-average conditions in the tropical
  Pacific through NH winter 2003-2004, although
  some indicate that weak El Niño conditions will
  develop by winter 2003-04.

Figure provided by the International Research
Institute (IRI) for Climate Prediction (updated
15 September 2003).
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Summary

• The 2002-2003 El Niño ended during March-April
  2003, as sea surface temperatures rapidly cooled
  across the central and eastern equatorial
  Pacific.
• Cooler-than-average surface and subsurface water
  temperatures developed in the east-central and
  eastern equatorial Pacific during late NH winter
  2002-03 and continued during NH spring 2003.
• The cooling trend reversed in late May-early
  June 2003.
• By early October 2003 conditions in the central
  equatorial Pacific were slightly warmer than
  average (but still ENSO-neutral).
• Recent observed trends indicate that El Niño
  conditions might develop before the end of 2003.
• Most statistical and coupled model forecasts
  indicate near-average conditions in the tropical
  Pacific through NH winter 2003-2004, although
  some indicate that weak El Niño conditions will
  develop by winter 2003-04.