This section provides information on El Niño and La Niña Years and its intensity based on sea surface temperature forecast in NINO3.4 region, which have high correlation to rainfall in Indonesia.
Sea Surface Temperature (SST) is an important element in coupled interaction of atmosphere and ocean in equatorial region of Pacific ocean. Based on historical record of ENSO events, SST patterns describe well the occurrence of ENSO events. Plots of STT pattern and occurrence of ENSO events reveal that certain range of SST value preceding development of an ENSO event, either El Niño or La Niña. Anomaly of SST (which explain variation from the average conditions) has long been known as a useful indicator to identify ENSO events. This system uses monthly running-average of SST anomaly of Niño 3.4 region (i.e., 5°N-5°S, 120°-170°W) in the analysis of ENSO. Threshold for identification of ENSO event is 0.5° of SST anomaly. Five consecutive months of SST anomaly +0.5°C or more is categorized as warm (El Niño) period, while -0.5°C or less is cold (La Niña). Further, strength of ENSO events are categorized into Weak (SST anomaly of 0.5-0.9°C), Moderate (SST anomaly of 1.0-1.4°C), and Strong (SST anomaly of > = 1.5°C).
The following graph and table show historical data of SST as well as forecasts made by dynamical and statistical models in the Niño 3.4 region. Note that prediction skills of the models, based on historical performance, vary one to another. The skills also gradually decrease as the lead time of forecast is increased. Other important point is also variation of skills along the year. In this context the skill of prediction is better in June - Dec compared to Feb - May. Differences among the forecasts of the models reflect both differences in model design, and actual uncertainty in the forecast of the possible future SST scenario.
ERSST v3b: http://www.cpc.ncep.noaa.gov/data/indices/ersst3b.nino.mth.81-10.ascii
ENSO predictions: http://iri.columbia.edu/our-expertise/climate/forecasts/enso/current/?enso_tab=enso-sst_table