WASHINGTON -- A long anticipated El Nino has finally arrived.

The National Weather Service on Thursday proclaimed the phenomenon is now in place. It's a warming of a certain patch of the central Pacific that changes weather patterns worldwide, associated with flooding in some places, droughts elsewhere, a generally warmer globe, and fewer Atlantic hurricanes. El Ninos are usually so important that economists even track them because of how they affect commodities.

But this is a weak, weird and late version of El Nino, so don't expect too many places to feel its effects, said Mike Halpert, deputy director of the weather service's Climate Prediction Center.

He said there may be a slight decrease in the number of Atlantic hurricanes this summer if the condition persists, but he also points out that 1992's devastating Hurricane Andrew in Florida occurred during an El Nino summer, so coastal residents shouldn't let their guard down.

There's about a 50 to 60 per cent chance the El Nino will continue through the summer, the National Oceanic and Atmospheric Administration predicts.

This is the first El Nino since spring of 2010.

Ever since March 2014, the weather service has been saying an El Nino was just around the corner. But it didn't quite show up until now. Meteorologists said the key patch of the Pacific was warming but they didn't see the second technical part of its definition -- certain changes in the atmosphere. Halpert said he didn't know why this El Nino didn't form as forecast, saying "something just didn't click this year."

For drought-struck California, it's too little, too late, meteorologists say.

Last year, some experts were hoping that El Nino would help the southwestern U.S. droughts because moderate-to-strong events bring more winter rain and snow to California -- even flooding and mudslides during 1998's strong El Nino. But this El Nino arrives at the end of California's rainy season and is quite weak, Halpert said.

Allan Clarke, a physical oceanography professor at Florida State University, said as far he's concerned, El Nino has been around awhile and the weather service didn't acknowledge it. But he agrees that this doesn't look like a strong one.