Although much of the globe could see dramatic temperature and precipitation changes because of "El Nino" weather patterns in the Pacific, Utah's weather should be about normal through the winter.
That's according to the National Weather Service's top long-range forecasters who discussed the El Nino phenomenon in a press conference Monday.El Nino - Spanish for "the child," so named because the weather pattern was first noticed around Christmastime in South America - is characterized by a large area of abnormally warm ocean water in the central and Eastern Pacific.
Although its causes are not fully understood, it changes the direction of jet streams and weather patterns globally, the weather service said.
"It is the most important annual climate event beyond the change of seasons," said David Rodenhuis, director of the Weather Service's Climate Analysis Center. "The jet streams and tropical storms are stronger and more intense during an El Nino, resulting in abnormal patterns of precipitation and temperature - from two to four degrees Fahrenheit."
Still, Weather Service forecast maps predict Utah should have about average precipitation and temperatures through March.But some of the changes brought by El Nino elsewhere include expected warmer than usual temperatures in the South, in Alaska and western Canada, but cooler than normal temperatures in much of the northern United States.
El Nino is also expected to produce drier than normal conditions in the Northwest and Northeast states, and wetter than normal weather in the Gulf and Southeast states.
"By studying similar past events, our scientists have discovered El Nino precipitation and temperature patterns which are highly consistent from one episode to another," Rodenhuis said.
"Since El Nino patterns tend to persist for several months, relatively accurate long-range forecasts (of one to three months) can be made for certain regions of the Earth. The Weather Service's winter outlook was formulated with the El Nino as in important ingredient," he said.
One of the problems for predicting weather in the Rocky Mountain and Great Basin areas, however, is that sometimes El Nino creates a split northern jet stream, and sometimes it does not, said Vernon K. Kousky, a research meteorologist.
If the jet stream does not split, it carries moisture to the north of the Rocky Mountain area resulting in drier than normal conditions.
But Kousky said the jet stream has been splitting so far, which he said results in equal chances for normal precipitation for the area.
Among some of the global changes from El Nino, Kousky said, the Philippines, Indonesia and northern Brazil are expected to be drier than usual. But southern Brazil and northern Argentina should be wetter than usual.
The weather service said El Nino occurs every three to five years. Sometimes it is mild, and sometimes it strongly affects weather patterns.
Other El Ninos have occurred in 1986-87, 1982-83, 1975, 1972-73, 1969, 1965, 1963 and 1957.