In another sign that El Niño is gaining strength and could soak California this winter, sea surface temperatures in the Pacific Ocean have increased to their highest level so far this year.
That temperature increase — 3.4 degrees Fahrenheit above the average — was recorded Aug. 5 by the National Weather Service's Climate Prediction Center at a benchmark location in the Pacific. That is slightly higher than it was Aug. 6, 1997, when it was 3.2 degrees Fahrenheit above normal.
The summer of 1997 was the prelude to the largest El Niño event on record. Storms that winter brought widespread flooding and mudslides, causing 17 deaths and more than half a billion dollars of damage. Downtown L.A. got nearly a year's worth of rain in February 1998.
"El Nino is already strong, and likely to get stronger by fall," Daniel Swain, climate scientist at Stanford University, said by email Wednesday. "Here in California, we'll still have to wait for the midwinter months for the main effects to arrive, but the likeliest outcome is still a wetter-than-average winter for most, if not all, of California."
Because El Niño's effects don't typically happen with great intensity in California in the summer, there probably won't be much drought relief for a while.
"Unfortunately, that means we still have to get through at least two to three more months of fire season and unabated severe drought conditions," Swain said.
That's bad news for firefighters, who are battling massive blazes this summer in Northern California. The fire season for Southern California typically hits a bit later in the fall with Santa Ana winds.
El Niño is a weather phenomenon that involves the warming of ocean waters west of Peru, which causes changes in the atmosphere that can dramatically alter weather patterns worldwide.
One effect of a strong El Niño is the shifting toward California of a subtropical jet stream that normally pours rain over the jungles of southern Mexico and Central America.
The National Weather Service's Climate Prediction Center is set to release its monthly El Niño forecast at 6 a.m. Pacific time Thursday.
For all the excitement about El Niño, Swain urged some caution.
"A wet winter is never a guarantee in California," he said. "I think a good way to think about it is this: There is essentially no other piece of information that is more useful in predicting California winter precipitation several months in advance than the existence of a strong El Niño event. But it's still just one piece of the puzzle. So while the likelihood of a wet winter is increasing, we still can't rule out other outcomes."