Why are we having Santa Ana conditions in May?

Just got another Santa Ana winds warning via phone app. Winds expected through Monday. The umpteenth such warning in the last few weeks. National meteorologist Dr. Jeff Masters laid out the harsh weather experienced in Southern California this week already: 

Record May heat sent temperatures soaring above 100° in much of Southern California on Wednesday, and fierce Santa Ana winds fanned fires that scorched at least 9,000 acres in San Diego County, forcing thousands to evacuate. For the second consecutive day, the Los Angeles Airport set a record for the hottest May temperature since record keeping began in 1944. Wednesday's 96° beat the record set on Tuesday of 93°. Other all-time May record heat was recorded at Camarillo (102°) and Oxnard (102°) on Wednesday. In Downtown Los Angeles, the mercury hit 99° on Wednesday, falling short of the all-time May record is 103° set on May 25, 1896. More record heat is forecast on Thursday, and hot offshore Santa Ana winds will bring extreme fire danger.

It's natural to suspect that clmate change might lead to an increase in hot dry Santa Ana winds, but interestingly the leading study on the question — from Alex Hall et al at the clmate lab at UCLA — found that during the traditional season for these winds they had actually decreased in recent decades. 

But that's from October to March. The Santa Ana winds experienced this week came in May.

That's all but unheard of. That's a fact.      

"I've lived here my entire life, but I've never seen these Santa Ana winds — these devil winds — in May," said Dianne Jacob, chairwoman of the Board of Supervisors [of San Diego County]. "We're now in a situation where there is a year-round risk of fire in San Diego County."

The science (from a study on Santa Ana forecasting) shows the accuracy of her observation. Almost no incidence of Santa Anas in May

Santaanaincidence

Further, the study also shows how rare it is for a Santa Ana condition to last for more than a day or two. 

Santaanaduration

Again, almost no examples of Santa Ana conditions lasting a week. We're in uncharted territory here, folks. Science has some interesting theories, but at this time we don't know why this is happening.

As a UC Berkeley researcher told National Geographic recently:

"What we're seeing right now is just a real anomaly," said Norman Miller, an expert in regional climate and hydrology at the University of California, Berkeley. "Whether it's part of natural variability or climate change, we need to have a longer record of occurrences so we can construct a trend and make sense out of it."

Meanwhile the LA Times (the on-line edition) came up with a great headline: 

Ash is the new "May Grey" in Southern California

And pics, too: 

Tomahawkfire

From the Tomahawk Fire near Fallbrook, east of San Diego. Still burning.

Related articles

Intense Santa Ana winds to continue Thursday
The Science Behind the Amazing, Terrifying Firenadoes in California
Ash is the new 'May Gray' in Southern California
Santa Ana winds, Ventura County, and fire: 2013

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