Complex interaction between atmosphere and warming oceans could unleash fierce weather events
Suzanne Goldenberg theguardian.com 5 Jun 14;
The chances of an El Niño, the global climate phenomenon that can destroy crops in Asia and offer a relief from harsh winters in North America, were raised to 70% on Thursday. But scientists said the coming El Niño was likely to be of only moderate strength.
In their monthly forecast, scientists from the US government's Climate Prediction Centre said warming sea temperatures in the Pacific continued to create the conditions for an El Niño this summer.
“The chance of El Niño is 70% during the northern hemisphere summer and reaches 80% during the fall and winter,” the centre said. Its ultimate strength had weakened over the last month. “Regardless, the forecasters remain just as confident that El Niño is likely to emerge,” the forecast said.
There has been growing anticipation of an El Niño this year – because of its widespread impacts.
In California, there has been hope that a strong El Niño could be a drought buster. The phenomenon is known for bringing wetter winters to Texas and southern California. They are also good news for Florida and the Caribbean, damping down the hurricane season in the Atlantic.
But El Niños can wreak havoc on fisheries in South America, and worsen droughts in part of Asia, Africa, and Australia.
That type of El Niño, with widespread global impact, has yet to fully materialise, the scientists said. While warmer sea temperatures in the Pacific were building conditions for an El Niño, the scientists said they were still not seeing the inter-action with atmosphere they would expect for a really big event.
“We are slightly favouring a moderate strength El Niño. While we are not ruling it out at this point, we are not expecting to see the next great El Nino,” said Mike Halpert, acting director of the Climate Prediction Centre.
Independent climate scientists said they too were expecting one of only moderate significance.
“We are going to have an E Niño. The question is the strength,” said Kevin Trenberth, a climate scientist at the National Centre for Atmospheric Research. “It hasn't taken off in the last month the way one might have thought if it was going to be a really major event.”
There was still time for a stronger El Niño to develop, however. It typically continues to develop over the summer months.
“We are on the precipice of actually having it here. The ocean has reached the minimum temperature but we are waiting to see the interaction with the atmosphere,” Halpert said. “It is certainly within the realm of possibility that it does become a very strong event but it would take some interaction with the atmosphere that we are not seeing right now.”
El Niño Likely: 70 Percent Chance by Summer
Becky Oskin LiveScience.com Yahoo News 6 Jun 14;
Time to place your bets: The chance of an El Niño developing this year continues to rise, forecasters with the National Atmospheric and Oceanic Administration said today (June 5).
NOAA's Climate Prediction Center (CPC) puts the odds of an El Niño at 70 percent this month and 80 percent during the fall and winter. But it's too soon to officially declare an El Niño, because the ocean and atmosphere are sending mixed signals, the CPC said in its monthly El Niño outlook, released today.
First, a quick definition: An El Niño is part of a natural climate cycle called the El Niño Southern Oscillation. The cycle swings between warmer water (an El Niño) to colder water (La Niña) in the eastern Pacific Ocean. [How El Niño Causes Wild Weather All Over the Globe (Infographic)]
During a potential El Niño year, scientists watch for unusually warm water in the eastern Pacific, along with weakening easterly trade winds, which usually block warm water from flowing toward the eastern Pacific.
Currently, wind and rainfall patterns don't quite match with a maturing El Niño. As warmer water moves eastward, so do the clouds and thunderstorms associated with it. Tropical rainfall patterns still haven't shifted away from Indonesia as expected during an El Niño year, the CPC said. Trade winds haven't slowed down yet, either, though the winds usually don't weaken until fall during an El Niño.
However, even though the atmosphere isn't showing strong signs of an El Niño, ocean temperatures have crossed the threshold that forecasters typically use to define an El Niño, the CPC said. Its latest measurements peg temperature anomalies between 1.1 and 2.9 degrees Fahrenheit (0.6 and 1.6 degrees Celsius), above the 0.9 F (0.5 C) threshold.
The missing atmospheric response to this warm water makes for a tricky forecast. The ocean is clearly heading toward an El Niño, but the atmosphere says "conditions neutral," the CPC said.
The CPC said significant uncertainty accompanies their outlook for strength: forecasters aren't sure whether this year's El Niño will be weak or strong. For now, models call for a moderate-size event.
But forecasters remain "just as confident that El Niño is likely to emerge," the CPC said.
El Niño is known for moving atmospheric moisture around the globe, causing snowy winters in the Northeast and wet winters in the Southwest. In turn, drought often strikes in Southeast Asia and Australia.
The next El Niño update will be released on July 10.
U.S. weather forecaster sees 70 percent chance of El Nino
Josephine Mason PlanetArk 6 Jun 14;
The U.S. weather forecaster said there was an increased likelihood of an El Nino weather phenomenon striking during the Northern Hemisphere summer in its monthly outlook on Thursday.
The Climate Prediction Center, an agency of the National Weather Service, said there was a 70 percent chance of El Nino, which can wreak havoc on global crops, during the summer and 80 percent during the fall and winter.
(Reporting by Josephine Mason; Editing by Lisa Von Ahn)
