It’s Santa Ana Season


There’s an interesting feature on the weather maps/charts this morning which will affect SoCal before the week is through.

FRIDAY AND SATURDAY WILL BE THE FIRST REAL SANTA ANA DAYS OF THE SEASON. — Southwest California Area Forecast Discussion, National Weather Service Los Angeles/Oxnard, CA

Santa Ana winds blow from the east through the mountain passes. They’re ‘katabatic’ or downslope winds, warming as they descend. Just like putting your finger over the end of a garden hose, squeezing these winds through the passes makes them stronger.

Starting Friday we’ll begin to feel hot, dry, strong wind.

In this area, which hasn’t seen widespread rain for months, Santa Ana winds represent extreme fire danger!

The BUFKIT chart at the top of this entry (click to get a larger view) is from the Monday 9/30/13 12Z GFS model for John Wayne Airport here in Orange County.

The timeline is opposite of what you expect. Today is on the right. As you look farther left you look farther into the future. The orange line is temperature, green line dew point and shading humidity.

On Friday morning the dew point plunges. High pressure is nosing into the region which will turn the wind from west to east. A very shallow layer of high humidity in place Wednesday and Thursday, the marine layer, will disappear. Its low clouds and gloom will be gone.

I did some quick back-of-envelope calculations from the chart at the top of this entry. With a Friday high of 88&#176 and dewpoint of 16&#176, the relative humidity will be around 7%. That’s extremely dry… crazy dry.

The danger of fires quickly spreading will be high. I expect to see Red Flag Warnings in place Friday.

Every area has its weather peril. This one’s ours.

It’s scary because fires can quickly grown beyond the ability to control them. It happens every year.

3 thoughts on “It’s Santa Ana Season”

  1. You are going to love the Santa Ana Winds. There were times when there NO moisture in the air. If you touched anything metal, you would get a shock. I had to wear a pot holder to turn the lights on & off. To provide some help, I would touch wood, so I could ground myself. It isn’t to bad close to the ocean, but if you live in the San Fernando, San Gabriel or San Bernardino Valleys, it is worse. That is when you’ll see fires and over turn trucks on the freeways. When you have lived in that area for 50 years, you experience everything So CA offers in the line of weather.

  2. So, if I understand you correctly, as a Weatherman you can forecast with 100% certainty that SoCal will NOT be getting an October Surprise Snowfall event like CT had last year, correct? HAHA

    Good luck with the fires.. You are right.. Being from CT all my life, I have no understanding of fire dangers such as what we see on TV every year out west.

    We get snow and hurricanes, you get fires and earthquakes.. Mother nature still has a way of telling people who is boss, she just “personalizes” it per location..

  3. Fire always scares me. I never understood how those winds were so much different there than here. The garden hose example made me totally ” get it!”….. Thanks, as always, for teaching me something new….:)

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