Can someone explain the Santa Ana wind?

[bubba]

I am reading about the weather out West and see predictions of a somewhat fierce Santa Ana wind event with gusts up to 55 MPH. It seems to have a relationship with cold air advection and interaction with the warmer Pacific. My understanding was that the Santa Ana was always hot air.

[Silas_Sancona]

46 minutes ago, bubba said:

I am reading about the weather out West and see predictions of a somewhat fierce Santa Ana wind event with gusts up to 55 MPH. It seems to have a relationship with cold air advection and interaction with the warmer Pacific. My understanding was that the Santa Ana was always hot air.

The * Warmer / Hot Air* aspect is directly related to ..or can occur as air from east of the coastal Mountains descends down slope through various passes / canyons towards the ocean. As air descends, it tends to warm and compress.. ( Hence the " rising, cooling air = low pressure; Descending, warming / compressing air = High Pressure"  terms ) It also tends to dry out as it moves from east or north east off the mountains / high deserts, and toward the coast west or south west of the mountains.

The events themselves begin as cool / cold air over the Great Basin is shoved ( Clockwise winds around High pressure area, centered over Nevada) west / southwest toward L.A. and the So Cal Coast.


In the winter, the colder / drier air being drawn toward the coast from further inland can help set up optimal conditions for radiational cooling when the sun goes down, especially in any wind sheltered locations or if / winds lighten for the night.

So, for instance, it could be windy ...and say reach 85F in Vista during a particular day in winter under a healthy Santa Ana event..  After the sun sets and the normal forces of air mixing, and other daily, local Wx aspects creating the pressure gradient responsible for the warm / windy afternoon subside, Temps can quickly fall down to the 40's or even reach freezing by the next morning under the right conditions / especially in favored areas.

Its one reason when we experienced "Diablo events" ..the S.F. Bay Area's sister to the Santa Ana's, you would want there to be some sort of breeze through the night.. to help keep the air mixed / warmer air mixed to the surface.. less chance for a frost / freeze.. It's also one reason hilltop locations can stay warmer at night compared to lower elevation spots in winter during downsloping wind events.

A big reason we didn't reach freezing here last night was because there was just enough of a breeze descending off the Rim overnight from the north east to help keep temperatures up in this part of town. Some spots north of Scottsdale didn't drop below 40F this morning, simply due to the breeze moving down off the mountains.  Yes, down sloping, Santa Ana -esque events also can occur in the Desert. Believe similar events occur along the Front Range in the Rockies.. Called by different name(s) of course.

[bubba]

Great explanation! Thank you Silas.