Sunday, January 14, 2007 El Niño nears its peak: NCEP By Stella A. Estremera
THE El Niño Phenomenon, which made itself felt in the second half of last year, is nearing its peak.
This was stated at the latest El Niño and Southern Oscillation (Enso) Diagnostic Discussion issued by the Climate Prediction Center of the US National Centers for Environmental Prediction (NCEP) dated January 11.
However, the Enso Diagnostic Discussion noted that El Niño conditions are likely to continue through May 2007.
"Most of the statistical and coupled models, including the NCEP Climate Forecast System (CFS), indicate that SST (sea surface temperature) anomalies are near their peak and that decreasing anomalies are likely during February-May 2007," the diagnostic discussion report said.
Still, drier than average conditions should be expected between January to March.
"Decreasing upper-ocean heat content in the central equatorial Pacific has been progressing east in association with the upwelling portion of the most recent Kelvin wave. In the absence of any further Kelvin wave activity, the upper-ocean heat content should return to near average in a few months," the report continued.
Kelvin waves are fluctuations in wind speed at the ocean surface at the Equator. It causes variations in the depth of the oceanic thermocline, the boundary between warm waters in the upper ocean and cold waters in the deep ocean. They play an important role in monitoring and predicting El Niño episodes.
However, there is yet another climate anomaly that may extend the drier-than-dry condition forecast as the Climate Prediction Center itself admits such outlook of a declining El Niño is uncertain because of "the resurgence of MJO (Madden-Julian Oscillation) activity in late December 2006".
MJO or intraseasonal oscillations are fluctuations in tropical rainfall that often go through an entire cycle in 30 to 60 days, very much shorter than Enso.
These oscillations have important impact on storminess and temperatures.
For this particular period, the report said, "It is possible that the enhanced precipitation phase of the MJO, which is currently entering the western tropical Pacific, might trigger a more persistent pattern of cloudiness and precipitation over the anomalously warm waters of the central equatorial Pacific during the next several weeks. If that occurs, then the equatorial easterlies over the central Pacific will likely weaken possibly leading to the initiation of a fifth Kelvin wave."
