HONOLULU -- Two storms are headed for Hawaii later this week in an unusual one-two punch that could be an effect of a developing El Nino pattern, the National Weather Service said.
The National Hurricane Center in Miami issued advisories Tuesday for Hurricane Iselle and Tropical Storm Julio.
Iselle could be hitting Hawaii by Friday and Julio two or three days after that, said James Franklin, the chief of hurricane specialists.
"There's enough uncertainty in the track that it's too soon to talk specific impacts," Franklin said.
Iselle is the ninth named tropical cyclone in the Eastern Pacific this hurricane season, CBS affiliate KGMB reports. The storm is expected to weaken.
"Right now it's a major hurricane but it will not be able to maintain that strength," Franklin said. "But it still could be at or near hurricane strength."
The outlook for Julio is more uncertain.
The Central Pacific Hurricane Center in Honolulu is taking over responsibility and would issue any hurricane watches or warnings.
Two big storms so close together in the eastern Pacific are rare but not unexpected in years with a developing El Nino, a change in ocean temperature that affects weather around the world.
"It's certainly pretty rare," Franklin said. "The central Pacific doesn't see nearly the activity that the Atlantic sees."
When an El Nino develops, "those are the kinds of years you see more activity," he said.
"You get more activity so the risk of impact goes up in El Nino years," Franklin said.