Joe’s Weather Blog: What are the Santa Ana Winds? (WED-12/6)

I’ll be talking about our weather locally (nothing aside from temperatures fluctuations are ahead it appears) but I also want to enlighten you about the situation that is grabbing national headlines today and will do so for several more days (at least). That would concern the devastating fires that again are occurring in California. More on that in the discussion.



Forecast:

Today: Becoming cloudy. Seasonable with highs in the mid 40s

Tonight: Turning colder with lows closer to 15-20°

Thursday: Coldest day of the fall/winter so far…highs around 32°

Friday: Partly sunny and chilly with highs in the 30s



Discussion:

We’ll get into the dry weather situation locally in tomorrow’s blog. There hasn’t really been any reason to deviate from a mostly dry forecast for the next 10 days or so. Whatever precip we get will be light and not amount to much. With us being on the edge of these cold air masses dropping SEwards from Canada…little ripples may be able to generate some flurries or patches of light snow…but right now nothing of note is expected through mid month at least…and perhaps even longer than that.

Tomorrow (Thursday) will be a colder day. I’m noticing (over the last 5+ days) that temperatures are exceeding expectations by a couple of degrees (or more)…and I’m wondering if the combination of brown and dormant vegetation and the worsening dry conditions is allowing us to maximize the fading sun angle heading into the 1st day of winter. Perhaps we’re tacking on 1-2° a day with this scenario. Yesterday we hit 47°…which was still above average even after a cold front…now we did have wind to create “mixing” and those winds were mainly from the west and WNW…which was a downsloping wind…but that’s still interesting to me.

The satellite picture taken yesterday shows the terrain condition. This is normal though for this time of the year…the lack of top soil moisture though may be slightly helping the temperatures a bit..maybe?

Picture via NASA Worldview

There aren’t any changes needed to the forecast. Right now Sunday looks to be the warmest day…with 50s likely and upside potential to 55-60°.

We’ll cool off a bit on Monday…and so it goes…dry…dry…dry.

Onto other things…by now you’ve probably have heard about the fire situation in Southern CA…here is the incident report filed earlier this morning…

The information above is probably outdated already because of how fast these fires are spreading aided by gusty winds.

We need to step back however a talk about some of the reasons why the fires are getting bad this season out there. One reason has to do with the amounts of moisture that southern CA received last year. While that part of the state didn’t get as much as what happened farther north…it was enough to kick start more vegetative growth. So when the typically dry weather came back later in the spring and into the summer>fall…that growth dies back…and dries out. This is fuel for wild fires.

Temperatures out there have been VERY warm as well for quite some time…running 4-8° above average…just since 10/1

Typically by now…they receive at least some moisture to help the cause a bit…but that has been mostly absent too for the last 2+ months (longer really). 5% of average rainfall is not good.

So it’s warm>hot…the air is bone dry…and there is a TON of “fuel” ready to burn. All you need is a “spark”…

That spark can be caused by strong winds…or humans or both. Strong winds can knock down power lines…or cause arcing of power lines…setting off fires…

Humans cause fires in a multitude of ways…something as simple as a flicked cigarette can get something big started when the winds kick in.

About the winds…they’re called Santa Ana winds and are created when there are large areas of high pressure dominating the western part of the country. Here is the latest weather map out there…

The map above shows isobars…or lines of equal pressure. See that 1046 and 1040 circles up towards UT and MT (or thereabouts depending on when you look at the blog today)…that is a strong area of high pressure.

Now remember the winds blow AWAY from high pressure and in a clockwise fashion…so the air is blowing out from that region of higher pressure…as it does so…in time it can be funneled through the various mountains and mountain ranges…and this accelerates the winds.

The air is pretty darn dry to begin with…but as the air flows through the mountains and comes down the slopes of the mountains it actually dries out even more and it gets warmer too…

So you have fast moving…warm…dry air flowing through the various canyons and passes out there…this creates the stronger winds that help spread the fires so quickly. The winds fan the flames…send embers miles away from the main fire source…new fires start and the pattern just keeps on repeating.

Out there there are ways for the fires to calm down…one way is a change in the wind direction…if the winds reverse…then the spread in fires slows dramatically. IF the winds switch, often out there that sends in higher moisture from the Pacific Ocean inland to a degree…this cools things off…and can help firefighters battle the fires somewhat easier.

Another factor of all this is what we’ve done…we’ve changed the land so much out there with buildings and homes etc…that these fires have the ability of causing more damage now than decades ago…plus you put houses into steeply terrained areas that firefighters have trouble accessing and now there are bigger problems.

No real rain out there is expected for several more weeks.

This satellite image shows the extensive smoke blowing out towards the Oeaan…this was provided by NASA yesterday.

It’s going to be a bad rest of the week out there…

Oh and there could be snow in the deep south over the next 48 hours…

Because of course…

Our feature photo comes from Dylan Hedrick from about 10 days ago out towards Richmond, MO

 

Joe

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