La Niña Still Hanging On

Sea surface temperatures in the equatorial Pacific for the week of April 10, 2011. Cooler-than-normal waters (blue) in the eastern tropical Pacific show the weakening La Niña. Click on the chart to go to an interactive version in the IRI Data Library.

Don’t write a eulogy for La Niña quite yet. “I thought it would die by this briefing,” said Tony Barnston, the chief forecaster at the International Research Institute for Climate and Society, last week.

At the climate briefing, which IRI holds every month, Barnston showed signs of La Niña are still observable in the equatorial Pacific. “Atmospheric aspects are still going strong,” he said. These aspects include altered atmospheric pressure and wind patterns over the tropical Pacific. In turn, these conditions have  been helping drive the recent above normal rainfall in Indonesia and Australia.

However, the telltale cooler ocean temperatures in the eastern equatorial Pacific associated with La Niña are starting to tail off, and with them, the possibility of the climate phenomenon continuing into the summer is also subsiding. IRI forecasters are predicting a 27 percent chance that La Niña will persist for the May-June-July season while the likelihood for a return to neutral conditions is 57 percent.

Climate models don’t agree about what is likely to happen for the rest of the year. Some show a second, weaker La Niña forming this fall, while others show a very weak El Niño or neutral conditions prevailing. The noise is due in part to the time of year. The period from February through May is commonly referred to as the spring barrier. During this time, models generally have the least skill to predict the coming season.Visit IRI’s ENSO Resource page for the latest forecast and information on the effects of El Niño and La Niña.