With extreme fire weather conditions expected starting Monday night, the National Weather Service has issued an unusual “particularly hazardous conditions” red flag for Los Angeles and Ventura counties for the next several days.
The last time a red flag for “particularly hazardous conditions” was issued for the region was just over a month ago on Election Day, when forecasters warned of extreme fire weather behavior. The next day, on November 6, a wildfire broke out in Ventura County, destroying more than 240 buildings, fanned by strong winds. It was the third deadliest wildfire in Southern California since 2013.
Before November, the last time the National Weather Service issued a red flag for Los Angeles and Ventura counties was in 2020.
Robbie Munro, a meteorologist with the National Weather Service, said red flag warnings for particularly dangerous conditions should only be issued once every three to five years, on average. But just like in 2020, it’s happening twice in the same wildfire season. The first time was in October and the other time was in December.
Mr Munro warned that “particularly dangerous conditions” were expected to begin around 10pm on Monday and last until 2pm on Tuesday. He said this extreme fire weather could be “comparable in magnitude” to the Nov. 5-6 Santa Ana howling wind event that fueled the wildfires.
Windy, dry, vegetation-drying conditions were the result of 2018 Thomas, the second deadliest in Southern California since 2013, when more than 1,000 structures burned in Ventura and Santa Barbara counties. It is similar to the situation that caused a fire. (The region’s most destructive fire during this period was the 2018 Woolsey Fire, which destroyed more than 1,600 structures in Los Angeles and Ventura counties.)
Why is this week’s weather forecast so dangerous?
(National Weather Bureau)
Forecasters will focus on the traditional Santa Ana wind corridor in Los Angeles and Ventura counties during this wind event.
Santa Ana winds occur at this time of year when high pressure forms in the Great Basin over Nevada and Utah and seeks a release valve off the coast where low pressure exists.
Under such extreme conditions, valleys and canyons can turn into wind tunnels. Sinking winds typically blow at high speeds in a northeast to southwest direction on their way to the beach. Wind gusts of up to 80 mph are possible, turning small fires into infernos, with embers burning at an alarming rate, leaving firefighters with little choice but to evacuate people.
(Paul Duginsky/Los Angeles Times)
A notable wind corridor in Santa Ana is that of the Santa Clara River Valley, which essentially funnels air from the high pressure system above the high desert, through Santa Clarita, and onto the Ventura County coast.
“If new fires start in these wind corridors, we would expect them to spread quickly,” Munro said. “Damaging winds may also cause scattered downed trees, power lines and power outages.”
Other areas susceptible to Santa Ana winds include the San Fernando Valley and the beaches between Ventura and Malibu.
(Paul Duginsky/Los Angeles Times)
Boaters should be aware of extreme winds, with the strongest winds expected from Ventura to Malibu and offshore to the Channel Islands. Strong winds are also expected in the San Pedro Strait and Santa Catalina Island. Munroe said waves 3 to 6 feet high and coastal flooding could hit eastbound ports such as Catalina Island.
Criteria for issuing a red flag warning, which is a particularly dangerous situation, include forecasts of sustained winds of 35 mph or greater and/or gusts of 60 mph or greater, single-digit relative humidity, and extremely dry vegetation. .
Peak gusts of 40 mph in Northridge, 44 mph in Oxnard, 48 mph in Fillmore, 52 mph in Westlake Village, 53 mph in Santa Clarita, 55 mph in Pyramid Lake and 60 mph in Acton. may occur. Munroe said strong winds could force Southern California airports to delay flights over the next two days.
Minimum relative humidity is expected to reach very low levels, just 5% in Oxnard, Fillmore, Westlake Village, and Northridge. In Ojai, it’s 6%. 7% in Downtown L.A., Santa Clarita and Pasadena.
A rolling red flag warning went into effect late Monday morning for much of Southern California, including the San Fernando and San Gabriel valleys, the mountains of San Luis Obispo County, the Inland Empire and large areas of the San State, and is expected to last through Wednesday. It is expected. Diego County.
Red flag conditions are expected across much of Southern California from Monday morning through Wednesday.
(National Weather Bureau)
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