ENSO Tracker
Official status of the El Niño–Southern Oscillation
About ENSO tracker
XThe current status of the El Niño-Southern Oscillation (ENSO) is determined by set criteria and expert analysis from Bureau of Meteorology climatologists. The tracker provides an early indication of the possible development of an El Niño or La Niña event, to aid effective planning and preparation prior to an event occurring. It is updated fortnightly.
Status unavailable
ENSO Tracker resets to NEUTRAL level
After approaching or exceeding El Niño levels in November–December 2014, the past four weeks have seen the tropical Pacific ease away from El Niño thresholds, indicating a return to neutral conditions. Likewise, all climate models favour neutral conditions to persist for the coming three months, indicating the immediate threat of El Niño onset is likely to have passed for the 2014–15 ENSO cycle. Therefore, the ENSO Tracker has been reset to NEUTRAL, and will remain at this level unless observations and models indicate a heightened risk of either La Niña or El Niño developing later in 2015.
How is the ENSO Tracker status determined?
The ENSO Tracker indicates the likelihood of an El Niño or La Niña occurring using a three-stage system. The status of the ENSO Tracker is determined by expert analysis from Bureau of Meteorology climatologists and using set criteria. For more details see the 'Criteria' and 'About' tabs.
Recent ENSO values
The graph below shows the fortnightly ENSO status from January 2000 to present.
Download ENSO status data
Further information
- Media
- media@bom.gov.au (03) 9669 4057
- Enquiries
- helpdesk.climate@bom.gov.au
The status of the ENSO Tracker is determined by expert analysis from climatologists and using the criteria set out below.
El Niño
El Niño WATCH
All of the following criteria need to be satisfied:
- Current climate state: ENSO phase is currently neutral or declining La Niña.
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-
Either:
SOI analogues: Of the 10 years that most closely resemble the current SOI pattern, 4 or more have shown El Niño characteristics. -
Or:
Sub-surface: Significant sub-surface warming has been observed in the western or central equatorial Pacific Ocean.
-
Either:
- Models: One-third or more of surveyed climate models show warming to at least 0.8 °C above average in the NINO3 or NINO3.4 regions of the Pacific Ocean by late winter or spring.
The chance that an El Niño will occur (based on historical data) is at least 50%.
El Niño ALERT
Any three of the following criteria need to be satisfied:
- Sea surface temperature: A clear warming trend has been observed in the NINO3 or NINO3.4 regions of the Pacific Ocean during the past three to six months.
- Winds: Trade winds have been weaker than average in the western or central equatorial Pacific Ocean during any two of the last three months.
- SOI: The two-month average SOI is –7 or lower.
- Models: A majority of surveyed climate models show warming to at least 0.8 °C above average in the NINO3 or NINO3.4 regions of the Pacific Ocean by the late winter or spring.
The chance that an El Niño will occur (based on historical data) is at least 70%.
EL NIÑO
Any three of the following criteria need to be satisfied:
- Sea surface temperature: Temperatures in the NINO3 or NINO3.4 regions of the Pacific Ocean are 0.8 °C warmer than average.
- Winds: Trade winds have been weaker than average in the western or central equatorial Pacific Ocean during any three of the last four months.
- SOI: The three-month average SOI is –7 or lower.
- Models: A majority of surveyed climate models show warming to at least 0.8 °C above average in the NINO3 or NINO3.4 regions of the Pacific until the end of the year.
Valid until the El Niño is officially declared over by the Bureau of Meteorology.
La Niña
La Niña WATCH
All the following criteria need to be satisfied:
- Current climate state: ENSO phase is currently neutral or declining El Niño.
-
-
Either:
SOI analogues: Of the 10 years that most closely resemble the current SOI pattern, 4 or more have shown La Niña characteristics. -
Or:
Sub-surface: Significant sub-surface cooling has been observed in the western or central equatorial Pacific Ocean.
-
Either:
- Models: One-third or more of surveyed climate models show cooling to at least 0.8 °C below average in the NINO3 or NINO3.4 regions of the Pacific Ocean by late winter or spring.
The chance that a La Niña will occur (based on historical data) is at least 50%.
La Niña ALERT
Any three of the following criteria need to be satisfied:
- Sea surface temperature: A clear cooling trend has been observed in the NINO3 or NINO3.4 regions of the Pacific Ocean during the past three to six months.
- Winds: Trade winds have been stronger than average in the western or central equatorial Pacific Ocean during any two of the last three months.
- SOI: The two-month average SOI is +7 or higher.
- Models: A majority of surveyed climate models show cooling to at least 0.8 °C below average in the NINO3 or NINO3.4 regions of the Pacific Ocean by the late winter or spring.
The chance that a La Niña will occur (based on historical data) is about 70%.
LA NIÑA
Any three of the following criteria need to be satisfied:
- Sea surface temperature: Temperatures in the NINO3 or NINO3.4 regions of the Pacific Ocean are 0.8 °C cooler than average.
- Winds: Trade winds have been stronger than average in the western or central equatorial Pacific Ocean during any three of the last four months.
- SOI: The three-month average SOI is +7 or higher.
- Models: A majority of surveyed climate models show cooling to at least 0.8 °C below average in the NINO3 or NINO3.4 regions of the Pacific Ocean until the end of the year.
Valid until the La Niña is officially declared over by the Bureau of Meteorology.
Neutral
NEUTRAL
An ENSO event is not active in the tropical Pacific Ocean and there are no signs of an El Niño or La Niña developing.
History of the ENSO Tracker
The below table summarises the ENSO Tracker status by month from 1980 to present.
ENSO status legend
| ENW | El Niño WATCH |
| LNA | El Niño ALERT |
| EN | EL NIÑO |
| LNW | La Niña WATCH |
| ENA | La Niña ALERT |
| LN | LA NIÑA |
| N | NEUTRAL |
El Niño and La Niña years
Shading of text in the year column refers to years in which El Niño (red) or La Niña (blue) events began.
Past ENSO events
Historical values of the ENSO Tracker status prior to 2014 are based on the set criteria alone. Values from the beginning of 2014 include expert analysis by climatologists at the Bureau of Meteorology to make the final assessment on a status level having been reached.
Using the ENSO Tracker
- The purpose of the El Niño–Southern Oscillation (ENSO) Tracker is to forewarn the Australian community of changes in the likelihood or risk of an El Niño or La Niña occurring, using a staged approach.
- The three stages of the ENSO Tracker are designed to reflect the level of confidence that climatologists and oceanographers have that an ENSO event may occur that year.
- An El Niño WATCH, for example, does not guarantee that an El Niño will develop – rather it indicates that the tropical Pacific Ocean is showing some signs that an El Niño may develop.
- For a stage to be reached, Bureau of Meteorology climatologists assess whether a set of atmospheric and oceanic criteria have been met, and that the current state of the climate system has reached that status level.
- No two ENSO events are the same. Some start earlier or later in the year than others. Some persist for over two years, while some only last several months. Most importantly, some have minimal impact on the Australian climate while others can cause severe drought or flooding over large areas of the continent. See the History tab and associated links for more details.
- When the ENSO Tracker reaches the ALERT stage, both the ENSO Tracker and the ENSO Wrap-Up may increase from fortnightly to weekly updates to ensure timely information is provided on the latest state of ENSO.
- Once an ENSO Tracker status level is reached, it remains valid until it is either increased to the next level or cancelled, or if an ENSO event has been declared, the event officially declared over. This is done by climatologists at the Bureau of Meteorology.
- Occasionally fluctuations in the atmosphere or oceans might mean that criteria that were met in the previous month may drop below criteria thresholds for the current month. Bureau climatologists determine whether or not this is likely to be a temporary fluctuation in which case the status will remain unchanged, or a permanent drop in the index, in which case the WATCH or ALERT may be cancelled.
ENSO Tracker verification
The ENSO Tracker system has been retrospectively assessed for each year since 1980 with the success rate summarised below. Important considerations relating to these figures include:
- The verification was undertaken using data that would have been available at the time. For example, when assessing for March 1982, only the monthly SOI/sea surface temperature data up to and including February 1982 was used.
- Limited model outlooks were available prior to 2000 so model hindcasts (i.e., running models based on past conditions) have been used to assess this criterion.
- The final decision to declare an ENSO Tracker status level (e.g., El Niño ALERT) is made by climatologists at the Bureau of Meteorology. As expert analysis by climatologists is not available for past assessments, the verification is based on the set criteria alone.
- Since 1980 there have been nine El Niño and eight La Niña events; this is regarded as a small sample size from which to draw statistics.
ENSO Tracker status: success rate
- Verification of the ENSO Tracker system found that for El Niño and La Niña events:
- About 50% of the time a WATCH was reached, an ENSO event subsequently occurred; and
- About 70% of the time an ALERT was reached, an ENSO event subsequently occurred.
Product Code: IDCKGEAS00
