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HOME > Expert Assessments > ENSO Diagnostic Discussion
issued by
February 5, 2002


Based on the observed oceanic and atmospheric circulation patterns and their recent evolution, and the time of year, it seems most likely that warm episode (El Niņo) conditions will develop in the tropical Pacific during the next 3 months.


The evolution towards a warm episode in the tropical Pacific continued during January 2002. By late January equatorial SST anomalies exceeding +1°C were observed in the vicinity of the date line from 170° E to 160 °W ( Fig. 1). Warmer-than-normal subsurface waters continued to expand eastward beyond the date line during the month (Fig. 2).

In recent months many tropical Pacific atmospheric and oceanic variables have been influenced by intraseasonal (30-60 day) fluctuations associated with the Madden-Julian Oscillation (MJO). Alternating periods of low-level easterly and westerly wind anomalies over the western and central Pacific have been consistent with this activity. December 2001 featured significant low-level westerly anomalies over the western and central equatorial Pacific. This activity generated a strong eastward propagating oceanic Kelvin wave that contributed to a deepening of the oceanic thermocline and warming of the sea-surface temperatures in the vicinity of the date line during January. Due to the ongoing Kelvin wave, an increase in subsurface temperature anomalies and SST anomalies is occurring in the eastern tropical Pacific. Localized warming of SSTs is expected along the coasts of Ecuador and Peru with the arrival of the ongoing Kelvin wave. It is important to note that this warming represents the early stages of El Niņo development and that mature El Niņo conditions will take several months to develop.

Strong MJO activity observed over the Indian Ocean and west Pacific during late January may contribute to another period of westerly low-level wind anomalies over the central and western equatorial Pacific during February. This may be the impetus for additional Kelvin wave activity that could arrive in the eastern equatorial Pacific by late March.

The latest statistical and coupled model predictions show a spread from near-normal to moderate warm-episode conditions during the next 3-6 months. All such models have relatively low skill during the transition phases of ENSO. While the majority of the prediction techniques do indicate that a warm episode will develop, there is considerable uncertainty as to its strength.

This discussion is a team effort of NOAA and its funded institutions. Weekly updates for SST, 850-hPa wind, OLR and the equatorial subsurface temperature structure are available on the Climate Prediction Center homepage at: (Weekly Update).  Forecasts for the evolution of El Niņo/La Niņa are updated monthly in CPC's Climate Diagnostics Bulletin Forecast Forum. To receive an e-mail notification when updated ENSO Diagnostic Discussions are released please send your e-mail address to:

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Page Author: Climate Prediction Center Internet Team
Page last modified: February 5, 2002
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