La Nina winter expected, but there's confusion

OAKLAND, Calif. (KTVU) - The California Department of Water Resources says chances are getting higher that we will have a La Nina over the winter, which might cause another heavy rainfall season like last year's La Nina. However, there's confusion over that.

Much of California's and the Bay Area's weather is dictated by the temperature of the Pacific Ocean off South America. A La Nina happens there when the water cools below its average temperature; an El Nino happens when the water warms above average.

"If you wanted to know one piece of information, in advance, in order to predict California precipitation, you would want to know whether it was gonna be and El Nino or La Nina year," said Stanford University Professor, Climatologist and Earth Scientist Noah Diffenbaugh.

"Those conditions, in those areas, impacts the trajectory of the Jet Stream which which carries our weather patterns to us in the middle latitudes," said Meteorologist Jan Null, founder of the Golden Gate Weather Service.

This year it's leaning towards a La Nina, often an indicator of a dryer winter. "But that doesn't guarantee that you would be able to accurately predict based on El Nino or La Nina," said Professor Diffenbaugh. In fact, our last drought year happened in a presumably wet El Nino year. Last winter's deluge came in a La Nina.

But, the long term prognosis for whacky weather is showing definite trends as the century wears on. "We will see more and more in the way of heat waves.  We will see more and more in the way of very severe storms," said Meteorologist Null.

In fact, more than 80% of the earth's surface that has reliable weather records is warmer now and global warming appears to be the main driver the consequences of climate change. "Extreme heat events, for example, extreme downpours extreme intense rainfall, extreme storm surge flooding," said Professor Diffenbaugh.

So, expect more multi-year droughts occasionally followed by winters like the last one as well as snow packs melting earlier. "That's exactly what we seen in the historical record. It's exactly what the climate models project for the future," said Diffenbaugh.

Both say we need to build more water storage, build better inland, bayside and seaside flood controls or possibly pay an awful price.