Comparing the different ENSO forecast models we conclude the first half of 2012 will most likely (on average) be dominated by the current La Niña phase. Most models however show progression towards neutral and some to El Niño before the onset of the boreal summer, while others show a more stable La Niña projection.
As for instance NASA reported on Thursday the ‘re-emerged La Niña’ of 2011-2012 is currently at peak strength. Most models forecast the La Niña will gradually weaken during the northern hemisphere spring months. Afterwards some models forecast a direct transition to El Niño, others show a lingering weak La Niña.
British forecast: La Niña strong up to March
[Left, middle.] Not all ENSO models show the lowest Pacific temperature anomaly (as indication of La Niña peak) in January. For instance the Met Office model at first has a flat-lining ensemble mean (for the Niño 3.4 region) until February-March 2012, after which weakening. According to the current Met Office ENSO run the transition to neutral state is likely to occur between April and June.
Australian forecast: strong and stable La Niña
[Right, bottom.] The strongest and most stable La Niña forecast is shown by the Australian Bureau of Meteorology, which predicts an average temperature anomaly of -1 Celsius up to June 2012 – and even an indication of a continued, yet weaker, La Niña up to September 2012.
European forecast: La Niña peaks now, slow transition to El Niño by summer
[Left, bottom.] The ECMWF ENSO forecast for Niño 3.4 shows al model runs climbing after a La Niña peak in January. The ensemble mean shows the neutral state will be reached in April and by July almost all runs point to a weak to moderate El Niño.
NASA’s forecast: peak at January-February, La Niña continues till July
[Right, top.] The ENSO model used by NASA shows some similarity to the Australian forecast as it predicts weak La Niña conditions will remain even after the northern hemisphere spring, but unlike the Australian model – and in agreement with all other forecasts NASA too shows a transition to a weak El Niño, which ensemble means shows from July 2012.
NOAA’s forecast: weakening but persistent La Niña – perhaps till October
[Right, middle.] The ENSO forecast of the NCEP model shows a clear weakening of La Niña to a negative temperature anomaly of 0.5 degrees Celsius (Niño 3.4) by April. After that the NCEP forecast shows continuation of weak (-0.25C) La Niña conditions up to October 2012, but by then model run variation is high.
Japanese forecast: steady route towards El Niño by July
[Left, top.] The ENSO model used by the Japan Meteorological Agency (for Niño 3 to 4) shows a La Niña peak in January, a transition to neutral ENSO state by the end of April and strong inclination towards a weak to moderate El Niño by July 2012.
© Rolf Schuttenhelm | www.bitsofscience.org