There are indications that an El Niño is on the way for the middle and latter parts of 2014. The phenomenon may impact the weather in portions of the United States, starting this summer.
Fluctuations in the sea surface temperature over the tropical Pacific Ocean have been observed and recorded for approximately the past 60 years. These fluctuations are known as the El Niño Southern Oscillation or ENSO. When the waters are cooler than average for a several-month period, the event is called La Niña. Opposingly, when the waters are warmer than average over several months, the event is called El Niño.
According to AccuWeather Long Range Forecaster Mark Paquette, "We are confident that an El Niño is in the early stages of developing and may reach moderate strength moving forward into mid- to late summer of 2014."
While El Niño will not have an impact on this spring and summer's severe weather, it may come on early enough and strong enough to have impact on the upcoming hurricane season in the Atlantic and Eastern Pacific.
Disruptive winds, known as wind shear, often develop off the Atlantic coast of the United States and sweep over a large part of the basin during El Niño.
"It is possible that a budding El Niño and developing wind shear may truncate the number of hurricanes originating from near the west coast of Africa during the middle and latter part of the season," Paquette said.
El Niño is generally not a major player in determining the number and strength of storms that originate over the Gulf of Mexico and much of the Caribbean.
While the number of storms tends to be lower in the Atlantic during an El Niño, it is not uncommon for the Eastern Pacific to have a very active hurricane season.
An El Niño may also enhance the summer monsoon over the Four Corners region of the Southwest as tropical moisture funnels in from the Eastern Pacific. Whether monsoon moisture is enhanced over drought-stricken California is less certain at this time, Paquette said.
However, there is some hope for rain later in the year that could impact the California drought, which has been weighing heavily on ranchers.
The greatest effects on the weather pattern in the Lower 48 states, including California, occur during the cold season.
"As far as impact on next winter, it is too early in the game to make a call one way or another, but some El Niño patterns in the past [1997-98] have produced significant storms in California," Paquette said.
El Niño winters are noted for wet and stormy conditions in the South and less-frequent, less-severe cold episodes in the Northern states.
The pattern has been known to bring outbreaks of severe weather in the South during the winter.
There is a tendency toward dry conditions in the Northwest and North Central states during an El Niño winter.
The strength of an El Niño can also have significant outcome of the weather pattern.
A strong El Niño can shift the winter storm track off the coast of the Northeast. A weak to moderate El Niño can allow the storm track to be near the coast.
Long-range weather forecasts are challenging, as many variables have to come together. Forecasts for the long range are typically described in overall departures from normal over a seasonal period rather than in daily extremes: wetter or drier than average and colder or warmer than average for a several-week to a several-month period.
AccuWeather will be releasing its summer 2014 outlook in late April along with a preliminary peek at the upcoming hurricane season.