By Paul Deanno

SAN FRANCISCO (KPIX 5) — Rain in July, summer storms in the Sierra, and recents days of much higher-than-normal humidity means the El Nino we have been waiting for is already here.

If the newest computer forecast models are correct, this will be just the beginning. It’s no longer a matter of “if.”  It’s a question of “how strong?”

“There is so much momentum still in the system that it is very likely that it’s going to intensify,” said Axel Timmermann, oceanography professor and El Nino expert.

The El Nino effect is a migration of warm water across the Pacific Ocean fueled by a series of westerly wind bursts. That warm water creates more thunderstorms and an altered path of the jet stream which can brings more drenching storms to California and the West Coast.

El Nino refers to the Christ child, so named because the effect is often seen around Christmas.

Timmermann says without a doubt, an El Nino pattern will be prevalent this winter. “I am not aware of any mechanism that would stop this El Nino event,” he said.

History shows that a weak or moderate El Nino does not bring the Bay Area increased rainfall.  Strong El Nino events give us a better chance of a wet winter, but only the “very strong” ones – the “cream of the crop” – have a track record of nearly doubling our average rain totals.

The very strong El Nino event most Californians remember is 1997-98.  It rained 27 inches in January and February alone.  Timmermann said this one could be even stronger.

“The fetch of this warm water is enormous, much larger than July 1997.”

But as promising as it sounds and looks, it’s important to remember that just because it happened before doesn’t mean it’ll happen the same way again.

There is no guarantee.  But there is an outlook – and for the first time in five years, it does appear right now that we are headed toward a wetter-than-average winter.



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