El Nino is back.

Government forecasters issued a report yesterday saying the weather system has arrived and will pummel the East Coast with blizzards and ice storms and exacerbate the extreme drought that has decimated corn, wheat and soybean crops in the Midwest. It also is expected to bring much needed rain to California.

Although they are still calling the system moderate, government forecasters said they expect the weather disruptions to be stronger and last longer than had been predicted last fall.

"This is a classic El Nino pattern," said Conrad C. Lautenbacher, administrator of the National Oceanic and Atmospheric Administration.

NOAA forecasters expect El Nino to alter weather nationwide through April.

It was expected to bring rains across the South, from California to the Carolinas. Those rains are already on the way.

A set of powerful rainstorms expected to hit California this weekend are the classic calling card of the weather pattern, El Nino experts said.

"We definitely have the makings of something here," said Bill Patzert, an oceanographer at the Jet Propulsion Laboratory in Pasadena, Calif., who said satellites that track changes in ocean temperatures now clearly show strong El Nino warming in a fat band around the equator. "It could really bring a soaking."

El Nino occurs when the waters of the equatorial Pacific remain warmer than usual for several months.

That warmth triggers atmospheric and weather changes around the globe, including floods in Ecuador and drought in Australia.

El Nino means "little boy" in Spanish. The weather pattern is named after the Christ child because South American fishermen first noticed the phenomena near Christmas.

This year's forecasting job has been tricky because the El Nino pattern did not start to develop strongly until a few weeks ago. NOAA forecasters, who predicted a moderate El Nino despite the lack of strong ocean warming this fall, ended up making the correct prediction.

The El Nino is not expected to bring quite as much rain to California -- or last as long -- as the El Nino of 1997 to 1998, which brought 31 inches of rain to Los Angeles in one year, Patzert said. That El Nino is blamed for 25,000 deaths worldwide, withering drought in Indonesia and widespread flooding in Peru.

This year's El Nino still could usher in a rainy winter. The moderate El Nino of 1992 to 1993 helped increase rainfall in Los Angeles that year to 27 inches.

"This is a good news forecast," said Patzert, who monitored the historic lack of rain in Southern California over the past year. "We need the water."