Scientists say that the El Nino effect is under way in the tropical Pacific.

Australia’s Bureau of Meteorology says a “substantial” El Nino event could take place before the end of the year.  Forecasters say that the El Nino is in early stages but the potential for extreme weather is real.

U.S. scientists initially said that El Nino had arrived but characterized it as “weak.”  Australian officials countered their U.S. colleagues’ claims.

“This is a proper El Nino effect, it’s not a weak one,” David Jones, manager of climate monitoring and prediction at the Bureau of Meteorology, told reporters. He said that El Nino could bring much lower than normal rainfall and enhance the country’s drought conditions.

“You know, there’s always a little bit of doubt when it comes to intensity forecasts, but across the models as a whole we’d suggest that this will be quite a substantial El Nino event.”

After the Australian model was released, U.S. forecasters on Thursday revised their statements and said that El Nino could bring much needed rain to California.

“We’ve seen continued evolution toward a stronger event,” NOAA official Mike Halpert told TIME. “Last month we were calling it weak, now we’re calling it borderline weak to moderate.”

“Stronger El Niños interrupt tropical rainfalls. That rain fall shifts and Indonesia and Austrailia become drier than average,” explained Halpert. “They’re not looking forward to El Niño shutting the tap off.”