High temperatures, low humidity this weekend in O.C. as firefighters tend Coastal fire

Fire personnel in Aliso Canyon fighting the Coastal fire might catch a break from the wind this weekend, according to meteorologists.

Authorities are investigating the cause of the fire, which began Wednesday afternoon and grew to at least 200 acres as of Thursday morning. The fire is believed to have been fueled in part by winds and dry conditions. Meteorologist Philip Gonsalves said Thursday afternoon the dry conditions and heat will continue to persist through the weekend, though officials at the National Weather Service in San Diego don’t forecast strong winds in the vicinity of the fire.

Temperatures are expected to be around the high 80s to low 90s, with the hottest day to be Saturday. Humidity will continue to trend downward — somewhere around the mid-teens to low 20s — through Saturday, but is expected to recover starting Sunday.

“In that part of Orange County, we typically don’t get humidity down into the teens in the day time unless we have a little bit of an offshore flow or maybe a Santa Ana [wind],” said Gonsalves, but added that it isn’t altogether an uncommon occurrence.

Gonsalves said the area is experiencing a diurnal wind.

A home burns along Coronado Pointe in Laguna Niguel on Wednesday, May 11, 2022.

(Scott Smeltzer / Staff Photographer)

“By that I mean, during the day, starting in the late morning and going through late afternoon, we’re going to have a sea breeze. With the sea breeze, we’re looking at wind gusts maybe as high as 20 miles an hour at times, but usually not that strong,” said Gonsalves.

“Now, the good news is at night the sea breeze drops off and we get a cold drainage wind,” Gonsalves continued. “That’s a very light wind that goes from uphill to downhill. Essentially what happens is the air at higher elevations gets colder faster. Because it gets colder, it starts to run down the slope. Sometimes, we call it down-sloping winds or just drainage winds.”

Gonsalves said the issue Wednesday was that there was a particularly strong sea breeze that fanned the Coastal fire. Once that dropped off overnight, firefighters were able to push back the flames. The sea breeze Thursday, Gonsalves said, was not as strong, allowing for firefighters to continue making the most of overnight gains.

As of Thursday afternoon, it was unclear the degree to which the fire had been contained, but Orange County Fire Authority Capt. Greg Barta said “crews were diligent and worked very hard throughout the night and we expect that to continue [Thursday].”

At least 20 homes so far have been destroyed. One firefighter was treated for injuries.

The National Weather Service had not as of late Thursday afternoon issued a smoke advisory for Orange County, though Gonsalves noted that the smoke produced Wednesday night was visible even on satellite imagery. The South Coast Air Quality Management District issued a warning overnight, saying that officials there did not expect the air quality to degrade past “moderate” except for in areas close to the fire.

County health officials encouraged residents to stay cool and drink plenty of water to combat the effects of the heat and smoke in a press release relating to the fire.

The Coastal fire is the second major wildfire in the area this year. In February, the Emerald fire burned through at least 145 acres.

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