Satellite imagery of the Palisades and Eaton Fires active in LA County, 09.01 Source: Copernicus Image of the day Credit: European Union, Copernicus Sentinel-3 imagery	Satellite imagery of LA County with smoke coming of the Palisades Fire, 11.01 Source: NASA Worldview	Accumulated precipitation over the US, until 28.01 06 UTC Source: wetterzentrale	Precipitation ensemble for Los Angeles, until 28.01 06 UTC Source: wetterzentrale

Wildfires
Los Angeles metropolitan area

Issued: Sunday, January 12, 2025, 11:00 UTC

Multiple large wildfires continue to be active in Southern California. The two largest fires, the Palisades and Eaton Fires, have burnt more than 150 km² in LA County. In total, more than 10,000 structures have been directly affected by the fires. The medium-range forecast for California shows little to no precipitation.

12.01.2025

The Santa Ana winds have subsided over Southern California as the high-pressure system over the Great Basin has dissipated. While the meteorological conditions have somewhat improved, multiple large fires remain active in the LA metropolitan area. The two largest fires, the Palisades and Eaton Fires are contained only to a low degree.

The Palisades Fire is spreading eastwards north of Santa Monica. Active in the hilly terrain north of Central Los Angeles, the fire is moving towards Bel Air and Hollywood districts. Since January 07, 2025, the fire has affected more than 5,000 structures burning an area of nearly 100 km^2. The Eaton Fire remains active in Pasadena and Altadena. In both towns, many historic buildings have been affected by the fire. In total more than 7,000 structures have been directly affected by this fire. Evacuation orders for the affected areas remain active, with more than 150,000 people being placed under an evacuation order. At least, 16 fatalities are related to the fires in Southern California.

Fire containment efforts remain difficult, although due to the lower wind speeds firefighting planes are active. The medium-range weather forecast does not show the potential for significant precipitation totals in Southern California. The ensemble forecast for the next two weeks for Los Angeles shows only very few precipitation signals. As a result, the fire season is expected to continue. Furthermore, the drought conditions in the southern part of the state are expected to worsen.

Webcam image at Mount Disappointment near Altadena facing southeastwards at the Eaton Fire, 09.01 07:50 UTC Source: ALERTCalifornia	Maximum total wind gusts over Southern California, until 09.01 18 UTC Source: Meteoblue	Accumulated precipitation over the US, until 20.01 06 UTC Source: wetterzentrale	Precipitation ensemble for Los Angeles, until 25.01 06 UTC Source: wetterzentrale

Wildfire, Santa Ana winds
Los Angeles metropolitan area

Issued: Thursday, January 09, 2025, 08:00 UTC

Multiple large fires are currently active in LA and the multiple neighboring counties. More than 2,000 buildings have been destroyed by the fires, with more than 100,000 people placed under evacuation orders. The Santa Ana winds fueling the fires are expected to subside later today. However, fire containment efforts remain difficult due to the ongoing drought conditions.

09.01.2025

A particularly strong Santa Ana Event has been affecting Southern California for the past few days. These downslope winds can not only reach hurricane-force strengths but also bring very dry air masses to the coastal communities of Southern California. The measurements at Santa Monica Airport highlight the degree of dryness of the air masses that the Santa Ana winds bring to LA County. On January 08, 2025, at 23 UTC, the dewpoint at the measuring site dropped to -40.6 °C. With an ambient temperature of 22.2 °C, the relative humidity dropped to below 1 %.

Currently, multiple large and destructive wildfires are active in LA County. The largest one by burnt area is the Palisades Fire near Santa Monica. The fire blazed through the coastal community of Palisades destroying more than 1,000 buildings including many ocean-front properties near Malibu. The Palisades Fire has already burnt more than 60 km². A second large fire is currently active east of Pasadena. The Eaton Fire burnt more than 40 km² and is located just outside of Altadena. More than 100,000 people have been placed under evacuation orders as the fire has already burnt hundreds of buildings in the community. Five fatalities have already been reported related to the fire. A third fire is active in the Hollywood Hills. As a result, parts of the Hollywood Hills have been placed under evacuation orders due to the Sunset Fire. Multiple other fires are currently active in the LA metropolitan area.

Throughout today, January 09, 2025, the synoptic set-up over the Western US will change. The driving high-pressure system over the Great Basin will move northwards. As a result, it is expected that the Santa Ana winds will subside during the day. This will facilitate fire containment efforts. However, the medium- to long-range forecasts indicate no significant weather pattern change over the Western US. Therefore, it must be expected that the drought conditions in Southern California will persist. In the precipitation ensemble for Los Angeles for the next two weeks, there are only sparse precipitation signals. This will likely elongate the fire season in California and worsen drought conditions.

Due to the high-value properties that are in danger of the multiple active fires in LA County, a significant economic loss is expected. Further, the smoke coming from these wildfires causes particularly poor air quality in the metropolitan area.

Webcam image at LACFD Helibase 69 Bravo E near Topanga Canyon facing eastwards at the Palisades fire, 09.01 09 UTC Source: ALERTCalifornia	500 geopotential and mean sea level pressure over North America, 09.01 06 UTC Source: wetterzentrale	Accumulated precipitation over California, since 01.10.2024 Source: CNRFC	Maximum total wind gusts over California, until 10.01 00 UTC Source: wxcharts

Wildfire, Santa Ana winds
Santa Monica, LA County

Issued: Wednesday, January 08, 2025, 09:00 UTC

Strong Santa Ana winds drive a large wildfire just north of Los Angeles. With a trough over Baja California, the synoptic conditions remain favorable for a prolonged period of Santa Ana winds. Further spreading of the Palisades fire must be expected.

08.01.2025

Santa Ana winds are strong downslope winds that occur in Southern California. They develop when a high-pressure system is located above the Great Basin. Combined with an elongated trough over Baja California, the synoptic scale winds along the southeastern side of the high-pressure system turn southwards. During these synoptic conditions, strong downslope winds can occur along the coastal mountain ranges of Southern California. Due to the large elevation changes these downslope winds can lead to a large temperature increase related to dry adiabatic lapse rate. In the narrow canyons through the coastal mountain ranges, the Santa Ana winds are channeled. At times, hurricane-force wind gusts can occur.

While these winds can induce potent heat waves in Southern California, they also bring very dry air masses to the coastal areas of Southern California. Combine these very dry air masses with high wind speeds and very favorable conditions for wildfires to arise. At 08 UTC, the relative humidity in LA County is as low as 6 % at Santa Monica Airport. The dewpoint at the measuring site has dropped to -21.7 °C while the ambient air temperature is up at 16.7 °C.

Furthermore, the start of the wet season in Southern California has been particularly dry this winter. Since the start of the water year on October 01, 2024, Southern California has seen little to no precipitation. As a result of prevalent dry conditions, the wildfire season has not ended. In combination with the very favorable synoptic set-up, a large wildfire developed on January 07, 2024, just outside of Los Angeles.

The Palisades fire is active in the northern suburbs of Santa Monica. The fire has already burnt 10 km² and more than 30,000 residents have been placed under evacuation orders. The synoptic set-up for the Santa Ana winds remains favorable until Thursday, January 09, 2025. Further spreading of the Palisade fire must be expected. Wind gusts of up to 100 kph make fire containment efforts particularly difficult. Due to the proximity to the LA metropolitan area further damage to residential areas is likely.

By the weekend, the high-pressure system over the Great Basin will move northwards as a trough plunges southwards east of the Rocky Mountains. As a result, the Santa Ana winds are expected to subside by Friday, January 10, 2025.