Special Issue with the EN Doubters in Mind!
ENSO Cycle: Recent Evolution, Current Status and Predictions
The following UPDATE is prepared by
Climate Prediction Center / NCEP – 31 August 2009
The latest weekly SST departures are:
- Niño 4 ~ 0.9ºC
- Niño 3.4 ~ 0.9ºC
- Niño 3 ~ 1.0ºC
- Niño 1+2 ~ 0.8ºC
El Niño Map. [SOURCE: NOAA/ Climate Prediction Center / NCEP]
Niño Region SST Departures (ºC) – Recent Evolution
Global SST Departures
During the last four weeks, equatorial SSTs were above-average in the Pacific and Indian Oceans. Also, above-average SSTs covered large areas of the Northern Hemisphere mid-to-high latitudes.
SST Departures (°C) in the Tropical Pacific During the Last 4 Weeks:
During the last 4-weeks, equatorial SSTs were at least 0.5°C above-average across the Pacific Ocean and at least 1.0°C above average near the Date Line and in the eastern Pacific.
Weekly SST Departures for the Last Four Weeks
- During the last four weeks, SST anomalies have increased in some areas of the equatorial Pacific Ocean.
- During the last month, the change in equatorial SST anomalies was slightly positive.
Central & Eastern Pacific Upper-Ocean (0-300 m) Weekly Heat Content Anomalies
Since April 2009, the upper-ocean heat content has been above average across the eastern half of the equatorial Pacific Ocean. The heat content was previously below-averagefrom mid-August 2008 through March 2009, with a minimum reached in late December 2008.
Sub-Surface Temperature Departures in the Equatorial Pacific
- During early July through late August 2009, positive sub-surface temperature anomalies weakened in the eastern half of the Pacific Ocean. Meanwhile, positive anomalies in the western Pacific have shifted eastward.
- The most recent period (below) shows positive anomalies across the equatorial Pacific, with the largest anomalies near 125m depth in the central Pacific.
Weekly Heat Content Evolution in the Equatorial Pacific
- During September 2008 –January 2009, negative heat content anomalies returned and then strengthened in the central and eastern equatorial Pacific as La Niña conditions redeveloped.
- The negative anomalies weakened during January-March 2009, with anomalies becoming positive since late March.
- In April 2009, the combined effects of an oceanic Kelvin wave and weaker easterly trade winds contributed to an increase in the upper-ocean heat content anomalies across the Pacific Ocean.
- Since April 2009, heat content anomalies have remained above-average.
- Recently, the downwelling phase of a Kelvin wave has shifted eastward.
Outgoing LongwaveRadiation (OLR) Anomalies
From February 2007-May 2009, 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 mid-May 2009, convection has remained mostly suppressed over the eastern Indian Ocean and Maritime Continent. During July 2009, convection was enhanced near the Date Line and over the western Pacific.
Pacific Niño 3.4 SST Outlook
- Most ENSO models indicate El Niño will continue through Northern Hemisphere winter 2009-10.
- The models disagree on the eventual strength of El Niño (SST anomalies ranging from +0.5°C to +2.0°C), but a majority of the models indicate at least a moderate strength El Niño (greater than +1.0°C) during November-December-January 2009-10.
Figure provided by the International Research Institute (IRI) for Climate and Society (updated 18 Aug 2009).
Summary
- El Niño is present across the equatorial Pacific Ocean.
- Sea surface temperatures (SST) remain +0.5 to +1.5 above-average across much of the equatorial Pacific Ocean.
- Based on current observations and dynamical model forecasts, El Niño is expected to strengthen and last through Northern Hemisphere winter 2009-10.
Typical US Temperature, Precipitation and Jet Stream Patterns during El Niño Winters
All images on this page are sourced from Climate Prediction Center/ NCEP/ NOAA.
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