El Niño event almost certain: BOM

El Niño event likely, says Australia’s Bureau of Meteorology

More evidence of a developing El Niño event has emerged during the past fortnight, and computer forecasts show there’s very little chance of the development stalling or reversing. —BOM

Equatorial sea-surface temperatures are currently more than 1°C above normal in the eastern Pacific, while the Southern Oscillation Index (SOI) remains below zero at around −2, says BOM.

A sustained negative SOI is often associated with El Nino conditions.

BOM hopes to provide a clear picture of the situation in the Pacific by next week when their final June data are analyzed.

El Niño events are usually (but not always) associated with below normal rainfall in the second half of the year across large parts of southern and inland eastern Australia.

Another adverse sign for southeastern Australian rainfall is the recent trend to positive values in the Indian Ocean Dipole (IOD), as measured by the Dipole Mode Index (DMI).

The next BOM update is available on July 8, 2009.

Last month FEWW reported US Climate Prediction Center as saying that conditions were favorable for a transition from ENSO-neutral to El Niño conditions during June – August 2009.

Click image to update and enlarge.

Images from Tropical Atmospheric Ocean project: NOAA

Summary of BOM Weekly Update:

• The Pacific Ocean sea surface is currently significantly warmer than the long-term average across most of the tropical Pacific, especially central to eastern areas.
• A large amount of the sub-surface water of the tropical Pacific is also warmer than the long-term average, particularly in the east.
• The latest 30-day SOI value is −2, while the monthly value for May was −5.
• Trade winds remain weaker than normal across the central equatorial Pacific.
• Cloudiness near the date-line is near-normal, and is yet to show a consistent trend towards El Niño conditions.
• All international climate models predict the tropical Pacific to continue to warm and to be above El Niño thresholds throughout most of the second half of 2009.

“Australia is the world’s fourth-largest wheat exporter and its grain production is still recovering from the worst drought in more than 100 years that reduced the 2006/07 crop to just 10.6 million tonnes and the 2007/08 crop to 13.0 million tonnes.” Reuters reported.

FEWW Moderators estimate that a new episode of El Niño, which would have devastating impact globally, could cause up to $500 billion in damages.

Related Links:

• El Niño could develop June – August 2009

• Recognizing El Niño
• El Niño and La Niña: Tracing the Dance of Ocean and Atmosphere
• TAO Diagrams

• El Niño Forecasts
• El Niño [Main Page]

See also comments section for latest updates.

El Niño could develop June – August 2009

UPDATE:

NOAA scientists today [July 9, 2009] announced the arrival of El Niño, a climate phenomenon with a significant influence on global weather, ocean conditions and marine fisheries. El Niño, the periodic warming of central and eastern tropical Pacific waters, occurs on average every two to five years and typically lasts about 12 months. See NOAA Press Release

The El Niño weather pattern can cause global weather chaos by exacerbating droughts and floods.

Conditions are favorable for a transition from ENSO-neutral to El Niño conditions during June – August 2009, US Climate Prediction Center says.

During El Nino, rainfall and thunderstorm activity diminishes over the western equatorial Pacific, and increases over the eastern half of the tropical Pacific. This area of increased rainfall occurs where the exceptionally warm ocean waters have reached about 28°C or 82°F. This overall pattern of rainfall departures spans nearly one-half the distance around the globe, and is responsible for many of the global weather impacts caused by El Niño.

El Niño occurs when the eastern Pacific temperatures rise above average, and the forecast says conditions are now favorable for a switch from ENSO-neutarl to El Niño conditions between June and  August 2009. The forecast warns that by end May 2009 sea surface temperatures (SST) had increased for the fifth consecutive month, rising to “above-average” in the  equatorial Pacific Ocean.

The 1997-98 El Niño/Southern Oscillation was one of the most severe ENSO events in history. It caused widespread drought in Australia and Indonesia and floods in S. America, especially Ecuador and Peru.

FEWW Moderators estimate that a new episode of El Niño, which would have devastating impact globally, could cause up to $500 billion in damages.

Graphical depiction of the four Niño regions. [Source: NOAA/  National Weather Service National Centers for Environmental Prediction Climate Prediction Center]

The report is available at EL NIÑO/SOUTHERN OSCILLATION (ENSO) DIAGNOSTIC DISCUSSION

For regular updates see comments section below.

Related Links:

• El Niño