El Niño may make a comeback later this year, impacting the weather across the United States during fall and winter.
A March 9, 2017, report from NOAA’s Climate Prediction Center stated that there is a 50 to 55 percent chance for El Niño to develop between July and December. If El Niño develops, it could have implications on the upcoming hurricane season and the overall weather pattern across North America into next winter.
El Niño occurs when the water temperature in the Pacific Ocean near the equator are warmer than normal for an extended period of time.
While signs are pointing toward El Niño returning, it is not a guarantee.
“Transitioning out of winter can be very difficult for the weather models to handle, so you can get misdiagnosed in the months of February, March and April especially,” AccuWeather Lead-Long Range Meteorologist Paul Pastelok said.
This uncertainty is sometimes referred to as the "spring barrier," since this time of year is when weather models that help to forecast El Niño are typically least accurate.
However, confidence is slowly growing that El Niño will develop this summer. It is not expected to reach its peak until late in the fall or early winter. Even if it does develop in the summer, it may take until the fall before more significant weather impacts are seen in the U.S., according to Pastelok.
There can be a lag between when the ocean water temperatures climb, as El Niño develops, and the influence over the U.S. weather pattern, Pastelok said.
El Nino may suppress Atlantic hurricane season
The timing of the onset of El Niño may play a key role with how active the upcoming hurricane season is in the Atlantic Ocean.
During an El Niño year, the winds at the mid and upper levels of the atmosphere are not favorable for the development of tropical system in the Atlantic hurricane basin, Pastelok said.
These disruptive winds can limit the number of tropical systems that develop, leading to a below-normal year.
With El Niño potentially developing late in the summer or early in the fall, these disruptive winds would have more of an impact on the second half of the season, decreasing the frequency of tropical systems in late-September, October and November.
“If El Niño does come on the way that it’s showing on the weather models right now, it may shut the season off early,” Pastelok said.
Eastern United States may see a snowy winter
The strength of El Niño will determine the impacts that it has on the eastern U.S.
While it is unlikely that another "super El Niño" will unfold like the pattern two winters ago, there could be a weak to moderate El Niño during the upcoming fall and winter.
During a stronger El Niño, storm systems typically track across the southern U.S. and out to sea rather than tracking up the East Coast. This lowers the chance of a major winter storm, such as a nor’easter.
However, if the pattern is weaker, systems may track farther north and could move up the East Coast, resulting in snow when enough cold air is present.
“The weaker the El Niño, the more favorable for impactful storms and snow in the East next winter,” Pastelok said.
Thus, a weaker El Niño could spell above-normal snowfall for cities along the I-95 corridor next winter, including in New York City and Boston.
Another wet winter may lie ahead for California
This past winter unleashed drought-busting rain and snow to California, and El Niño could yield another wetter-than-normal winter for the state.
“An El Niño typically leads to more storms targeting California since the jet stream and resultant storm track dips southward across the state and pulls in tropical moisture,” AccuWeather Senior Meteorologist Kristina Pydynowski said.
Additional rounds of flooding similar to that of this past winter could ensue, but rainfall can also eliminate lingering drought conditions.
“It would be very beneficial for moisture to come from the Pacific Ocean right into extreme Southern California and western Arizona to moisten that area up to completely eliminate the drought that they’ve had,” Pastelok said.
El Niño-driven rain in this area could also help to replenish Lake Meade, the water reservoir created by the Hoover Dam. The water level on this lake has dropped over the past several years due to drought.
While another wet winter may unfold for California next year, it is not likely to be as wet as this past winter.