Sunday, February 9, 2014

Increasing chance of El Nino and drought later this year

Enjoy the rain in Hawai`i the last couple of months, because there’s some evidence that later this year we could face the opposite: unusually dry conditions.

Researchers are detecting an increasing likelihood that we’ll be moving into an El Nino climate condition in the second half of this year. One of the hallmarks of an El Nino in Hawai`i is winter and spring drought. Another is increased tropical cyclone frequency.

(Image: Noaa water temperature chart from the extreme El Nino event of 1997. Credit: NOAA.)

In its Feb. 6, 2014, El Nino diagnostic discussion, U.S. Climate Prediction Center said that after the spring, there appears an increasing likelihood of a new El Nino event. 

While warning that El Nino forecasts are notoriously hazy in the spring, the CPC says “an increasing number of models suggest the possible onset of El Niño. Strong surface westerly winds in the western Pacific and the slight eastward shift of above-average temperatures in the subsurface western Pacific potentially portend warming in the coming months.”

The CPC report follows on the heels of a similar prediction January30, 2013, by the World Meteorological Organization.

The WMO cited models that predicted Nino-neutral conditions through the spring, and chances of continued neutral conditions or a weak El Nino in the third quarter of the year.

The Australian Bureau of Meteorology chimed in even earlier, on January 28, 2014, with great caution, but a suggestion that neutral conditions could remain in place into the fall, but that El Nino warming could ease into place toward the end of the year. 

“Most climate models surveyed by the Bureau suggest the tropical Pacific Ocean will warm through the southern autumn and winter. Some, but not all, models predict this warming may approach El Niño thresholds by early winter. Model outlooks that span autumn have lower skill than forecasts made at other times of the year, hence long-range model outlooks should be used cautiously at this time,” the Australian service reported.

Thus far, none of the prediction services are proposing that the El Nino, if it comes, will be a strong one. But they sometimes are, and one group of researchers suggests we’ll be seeing more of those.

It was 15 years between an extremely strong El Nino in the 80s and the one in the late 90s, and it’s been a similar period of time from then till now. A paper in the journal Nature Climate Change notes that extreme El Ninos occurred in 1982-83 and again in 1997-98.

That paper suggests we could be seeing more of those in the future, thanks to climate change. In fact, we could see twice as many extreme El Nino events as we see now, the authors argue. 

“The increased frequency arises from a projected surface warming over the eastern equatorial Pacific that occurs faster than in the surrounding ocean waters, facilitating more occurrences of atmospheric convection in the eastern equatorial region,” they write.

© Jan TenBruggencate 2014

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