A sundowner is a northerly

offshore wind Offshore wind power or offshore wind energy is the Electricity generation, generation of electricity through wind farms in bodies of water, usually at sea. There are higher wind speeds offshore than on land, so offshore farms generate more elect ...

California California () is a U.S. state, state in the Western United States that lies on the West Coast of the United States, Pacific Coast. It borders Oregon to the north, Nevada and Arizona to the east, and shares Mexico–United States border, an ...

along the southern Pacific slope of

Santa Ynez Mountains The Santa Ynez Mountains are a portion of the Transverse Ranges, part of the Pacific Coast Ranges of the west coast of North America. It is the westernmost range in the Transverse Ranges. The range is a large fault block of Cenozoic age created ...

, in communities along the Gaviota Coast and Santa Barbara towards but not including

Ventura County Ventura County () is a county located in the southern part of the U.S. state of California. As of the 2020 census, the population was 843,843. The largest city is Oxnard, and the county seat is the city of Ventura. Ventura County comprises ...

Formation

It occurs when a region of high pressure is directly north of the area, the coast of which trends east–west. This contrasts with the more typical onshore flow. The winds blow with greatest force when the

pressure gradient In hydrodynamics and hydrostatics, the pressure gradient (typically of air but more generally of any fluid) is a physical quantity that describes in which direction and at what rate the pressure increases the most rapidly around a particular locat ...

is perpendicular to the axis of the Santa Ynez Mountains, which rise directly behind Santa Barbara. These winds often precede Santa Ana events by a day or two, but also as tail end of Santa Anas after they weaken, it is normal for high-pressure areas to migrate east, causing the pressure gradients to shift to the northeast. Aptly named sundowners are typically nighttime events that terminate after sunrise, they may repeat for days, while Santa Anas are multi-day long events. Weaker sundowner effects may occur without an associated Santa Ana event, at times due to a

Diablo wind Diablo wind is a name that has been occasionally used for the hot, dry wind from the northeast that typically occurs in the San Francisco Bay Area of Northern California during the spring and fall. The same wind pattern also affects other parts ...

event (Northern California), akin to a foehn wind.

Fire dangers

Sundowners are particularly dangerous during

wildfire A wildfire, forest fire, or a bushfire is an unplanned and uncontrolled fire in an area of Combustibility and flammability, combustible vegetation. Depending on the type of vegetation present, a wildfire may be more specifically identified as a ...

season because the air heats and dries as it descends from the mountains to the sea. Gale force hot, dry winds can make firefighting impossible. A sundowner quickly burned a swath from the mountains through populated areas and across Highway 101 into Hope Ranch during the 1990 Painted Cave Fire. The most intense periods of the Jesusita Fire's destruction have also been blamed on sundowner winds. The Sherpa Fire grew to overnight due to the sundowner winds, destroying the water system for El Capitán State Beach at the beginning of the 2016 fire season.

Origin

The etymology of the word ''sundowner'' is uncertain, but it may derive from the Spanish term '' zonda,'' or from the

Arabic Arabic (, , or , ) is a Central Semitic languages, Central Semitic language of the Afroasiatic languages, Afroasiatic language family spoken primarily in the Arab world. The International Organization for Standardization (ISO) assigns lang ...

simoom Simoom ( ''samūm''; from the root ''s-m-m'', "to poison") is a strong, hot, dry, dust-laden wind. The word is generally used to describe a local wind that blows in the Sahara, Jordan, Iraq, Syria, and the deserts of Arabian Peninsula. Its t ...

'', which are both similar wind phenomena. It is also typically the case that sundowner winds commence in the evening near sunset, when onshore sea breezes abate and offshore flows such as the sundowners pick up.

Temperature inversion

As sundowner events typically happen near nighttime or during nighttime, when coastal temperatures die down, there can be a sharp temperature difference in monitoring stations merely blocks away, due to elevation difference. Higher elevations of hills can correlate with huge temperature rises compared with lower elevations, and can rival those seen in daytime heatwaves --- coastal inversion layer kept beaches (Pacific side of San Francisco) some 40 to 45 degrees fahrenheit cooler than hills at 2500 or 5000 feet (Mount Tamalpais) on afternoon of July 6, 2024. Sundowners have caused similarly intens
sharp temperature contrasts
akin to these daytime inversion layers, but surprisingly at close to midnight, where California State Route 192 approximates the hot vs cool dividing line, in the Santa Barbara area.

References

{{reflist Winds Climate of California Natural history of Santa Barbara County, California Santa Ynez Mountains Santa Barbara, California Weather events in the United States

Formation

Fire dangers

Origin

Temperature inversion

See also

References