Global sea surface temperature anomaly. (NOAA/ESRL)

Earlier this year, forecasts were hot and heavy on the development of El Niño. Conditions seemed favorable, and California is praying for a wet winter given the continued drought conditions. However, the trends shifted in the spring, thus leaving us wondering – is this El Niño really going to come to fruition? Forecasters (and the atmosphere) are waffling somewhat.

In an update on Thursday, scientists at the Climate Prediction Center continued to issue favorable odds  of an El Niño developing this year (70 percent chance this summer, 80 percent by early next winter), and an El Niño watch remains in effect. However,  they suspect this El Niño’s intensity to only reach weak-to-moderate strength, which is a far cry from the “super El Niño” that some forecasters  once thought was possible.

At its core, El Niño is the warm phase of a sea surface temperature pattern near the equator in the Pacific Ocean.  Right now, water temperatures are above normal in all the right regions, however, they’re not warm enough yet for scientists to officially declare it an El Niño event.

Time series of ocean heat content anomaly over the past year. After a spike in temperature early this year, the ocean heat content in the Pacific has been steadily declining. (Climate Prediction Center)
Time series of ocean heat content anomaly over the past year. After a spike in temperature in early 2014, the ocean heat content in the Pacific has been steadily declining. (Climate Prediction Center)

Paul Roundy, a professor of atmospheric science at the University at Albany, hypothesizes that the current “neutral” state is actually a warm phase (El Niño) with a cooler anomaly layered on top. He suspects that as this cool anomaly begins to wane, El Niño will pop through:

Think of [this] as a few weeks of colder conditions superimposed on a background of warm conditions. The combination of these two signals yields an impression of a condition near normal, but the cool conditions do not last as long, and after they move out of the equatorial region or dissipate, the warm state is left behind.

Weather Underground’s Jeff Masters suggests that the atmosphere is presenting El Niño signs. He writes on Wednesday:

Heavy thunderstorm activity over Indonesia and near the International Date Line is typically enhanced during an El Niño event, and has been picking up over the past month, but must increase more before we can say the atmosphere is responding in an El Niño-like fashion.

Early in 2014, a burst of favorable wind activity in the Pacific led some forecasters to believe that a strong El Niño was just around the corner. Winds typically flow east to west in the tropics, but sometimes bursts of wind in the opposite direction will grease the wheels for El Niño. This wind pushes warm water toward South America, and aids in the development of an El Niño event.

However, that pattern reversed in the spring. Winds began to flow strong from east to west, which causes upwelling of cooler water along South America. This dampened El Niño forecasts, which have steadily declined in intensity.

Model forecasts for El Niño and La Nino. Most models are forecasting El Niño conditions to begin this summer/fall, and a few are forecasting neutral conditions. (Climate Prediction Center/International Research Institute for Climate and Society)

While he agrees with the Climate Prediction Center that El Niño is likely this year, Roundy cautions that El Niño forecasts continue to be tricky business with all the moving pieces that need to be considered. “The ocean state is constantly changing as it interacts with forcing from winds associated with weather events,” Roundy says. “Since weather events influence El Niño, and since such events are not completely controlled by the developing El Niño, we cannot know for certain how a given El Niño event will evolve.”

El Niño has a wide range of impacts on global weather. It can alter precipitation patterns over the U.S., and it can decrease the likelihood that hurricanes will develop in the Atlantic. California remains in one of its most intense droughts in recent history – 79% of the state is in extreme drought, and nearly 40% is in exceptional droughtaccording to the U.S. Drought Monitor. So it’s no wondering that Californians are waiting with bated breath for a strong El Niño event, which has had some historical success at producing heavy winter rain and snowfall along the West Coast. In particular, the 1997-1998 El Niño was a record-breaker for the state.

Unfortunately, Weather Underground’s Christopher C. Burt cautions against getting our hopes up for a stellar California rainy season:

These hopes have little basis in reality since only very strong El Niño’s, like the last one of 1997-1998, actually impact seasonal precipitation across the entire state. Current models indicate the coming El Niño will be of only ‘moderate’ strength. This may have an impact on the southern third of the state but, historically, moderate El Niño’s have not influenced rainfall patterns one way or the other for the northern two-thirds of California.