"Things have been gathering steam for a while," said Roger Lukas, a professor of oceanography at the University of Hawai'i.

An El Nino is associated with a large pool of warm water that moves along the equator from the western Pacific to the east. There are changes in rainfall, in fisheries and in weather patterns in distant places such as North America, Africa and Asia.

Ocean temperatures along the South American coast in February had warmed by 4 degrees Fahrenheit above normal. In Peru, scientists have reported that warming conditions have caused the cold-water anchovies to leave their normal waters off the coastal nation. They have been replaced by warmer-water species, the National Oceanic and Atmospheric Administration said.

"This warming is an additional sign the Pacific Ocean is heading toward an El Nino condition," said NOAA Administrator Conrad C. Lautenbacher.

"It's still too early to determine the potential strength of this El Nino or exactly what weather conditions it will bring to the United States, but it is likely these warming conditions in the tropical Pacific will continue until early 2003," he said.

Lukas said his review of the data brings him to the same conclusion.

"Warm sea surface temperatures are almost everywhere along the equatorial Pacific" and the western Pacific pool of warm water is on the move eastward, already having crossed the International Date Line, he said.

The primary remaining issue for climate experts is to determine how strong this El Nino will be. The early consensus is that it will be a weak to moderate event, Lukas said.

"It is unusual to have very strong events right next to each other" and the last El Nino, in 1997 and 1998, was a powerful one, he said.

El Ninos occur about every four to five years and can last from 12 to 18 months. Before the 1997-98 event, previous strong El Ninos occurred in 1982-83 and 1972-73. For Hawai'i residents, El Nino statistically is associated with somewhat drier weather in winter, and with an increased likelihood of rotating storms, and with stronger storms.

The main impact of El Nino in South American waters is often felt in the fisheries around Christmas time, prompting people in that part of the world to have named it El Nino, or the child, a reference to the baby Jesus.

The Associated Press contributed to this report.

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