After a long year of scientists’ predictions, the National Oceanic and Atmospheric Association (NOAA) finally announced that El Niño has arrived, with an almost 60 percent chance that it will extend over the summer months.
The El Niño is a term describing the ability of the tropical Pacific of affecting the atmosphere by raising the sea surface temperatures to be warmer in the central equatorial Pacific. It is part of the El Niño Southern Oscillation, which is a cycle of natural variability in the Pacific.
There’s a reason why the ENSO events always make the news, and it’s because they can predict warmer, cooler, drier or wetter weather in different regions of the world. The areas around the tropics are most influenced, but mid-latitudes can also be affected.
The largest effects fall on Peru, which usually experiments flooding. As a matter of fact, Peruvian fishermen were the first to notice the climate change. Because the peak of the phenomenon hits around the Christmas holiday, they decided to call it El Niño (the baby).
A widely accepted theory is that El Niño causes more frequent extreme weather. However, researchers have discovered the theory does not apply on a global scale as much as it does in very specific regions. But because of predictions and known interactions, scientists can anticipate a lot easier the effects of El Niño. Consequently, concerned authorities can also use the event indicators to better prepare, and even take advantage of the beforehand knowledge.
On the United States’ part of Pacific, a NOAA team is responsible to observe the current conditions in and around the tropical Pacific Ocean. They establish El Niño’s status by combining real conditions with predictions generated by computer models about the event’s development over the next months.
Borderline El Niño conditions have been announced since last October, but this month is the first one when scientists are officially calling the happening of El Niño event.
Tony Barnston, leading forecaster at the International Research Institute for Climate and Society (IRI) and member of the ENSO forecast crew, explains that changes in the atmosphere are starting to show more than borderline status for El Niño, enough pass onto the next, weak phase.
The ENSO system works by combining both the ocean and the atmosphere, so they have to interact before El Niño can strengthen its conditions. The sea surface temperatures have been in the grid for what’s considered El Niño for several months now, but scientists could not call the event before the atmospheric conditions joined the ocean’s.
According to Michelle L‘Heureux, meteorologist at NOAA’s Climate Prediction Center (CPC) and head of the ENSO forecast team, El Niño is rather difficult to pin down during this season, because it oscillates a lot from borderline to weak and back. The event will be easier to document once it hits its peak, because indexes eventually end up on the same page.
Not everyone is certain that the year’s El Niño event is here to stay. The Australian Bureau of Meteorology is still two levels away from an alert of an official El Niño declaration. On the U.S. side of the matters, El Niño might not get a chance to show its full potential, because it usually has the most effect in the winter months.
L‘Heureux ruled out the possibility of great influence over the U.S. during March and April, saying that most affected areas will probably be the global Tropics. At this point, however, the indexes are very weak, so even those areas are still unaffected. She added that during the upcoming hurricane season, El Niño’s development will be closely observed.
One of the easiest-to-spot signals of El Niño is heavy rain across the southern U.S., closely seconded by above-average temperatures in southern Alaska, dry weather in the Pacific Northwest and Ohio Valley and slightly cooler temperatures in the Southeast.
According to Mike Halpert, deputy director of NOAA CPC, the current outlook for the southeastern United States is consistent with El Niño conditions, as the chance of precipitation over Florida has increased for the next several months. However, even if it’s indeed consistent, it’s rather difficult to attribute it to El Niño beyond any shadow of doubt.
During this last year’s predictions, scientists have discussed the potential scenario in which El Niño would increase the possibility of rain over the drought-stricken California. However, Halpert assessed that even if El Niño conditions strengthen, it might be too late for those hoping for relief, as the rainy season is dying down. California can hope for rain if the El Niño event continues over the next months, into the summer season. The ENSO team is going through the worst time of the year for predictions, so uncertainty is still at high levels.