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ENSO Cycle: Recent Evolution, Current Status and Predictions

This report provides an overview of the recent evolution of the El Niño-Southern Oscillation (ENSO) cycle, including the 2002-2003 warm episode and current conditions. It also presents the Pacific sea surface temperature outlook and predicts near-average conditions in the tropical Pacific through NH winter 2003-2004.

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ENSO Cycle: Recent Evolution, Current Status and Predictions

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

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

  3. Overview • The 2002-2003El 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.

  4. 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

  5. U850, OLRa, Niño 4

  6. The 2002-03 El Niño: Historical Perspective

  7. Seasonal SST Anomaly Patterns

  8. Seasonal Precipitation Anomaly Patterns mm/d

  9. Seasonal 200-hPa Height Anomaly Patterns

  10. NH Monthly 500-hPa Height Anomaly Patterns

  11. Niño Indices: Recent Evolution SSTs increased to 0.5°C or more above average in the equatorial Pacific (Niño 4, Niño 3.4 and Niño 3 regions) by early October 2003.

  12. SST Anomaly Difference: May to September 2003

  13. 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 in the region between 110°W and 150°E. • 14 September-11 October 2003

  14. 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).

  15. Recent Evolution of Subsurface Conditionsin 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.

  16. 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.

  17. NCEP Consolidated Niño 3.4 Forecast

  18. 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).

  19. Summary • The 2002-2003El 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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