Tuesday, October 29, 2019

A Surge of Cold, Dry Air Envelopes the Northwest and Now Threatens California

Last night, very cold, dry air surged southward out of Canada, pushing into Washington and Oregon.

The pressures, temperature, and wind map for 8 AM this morning tells the story (below). The blue is cold air, with the primo stuff east of Cascades.   Note the large pressure difference across the Cascades, which resulted in strong easterly winds in the Columbia Gorge and in Cascade mountain passes.


If you are in Washington State, do you feel under pressure?  You should, since we have usually high pressure at the surface right now.    For example, at Ellensburg, in the central portion of the State, the sea level pressure is higher than any other time in the last six months, reaching nearly 1040 hPa (mb).


And how about your skin?   Does it feel kind of dry?  It should, sicne e have some of the driest air in a very long time over us--yes the driest since the start of the year--as indicated by the very low dew point temperature at Sea Tac Airport.    Dew point is a good measure of the amount of water vapor in the air (and it is the temperature at which air becomes saturated when cooled).  This morning it got down  below zero (in fact, -4F).   Mama Mia...that is super dry.  Even drier than the arid period last March when downslope winds started fires around western Washington. 

The large pressure difference across the Cascade resulted in easterly winds accelerating to 50-60 mph around Enumclaw and Tacoma today and similar winds around the Columbia Gorge and some of the highest hills in eastern WA (see below, click to expand).


As a result, there were some power outages in the south Sound today (some still going on)

With very dry air above, the greenhouse warming effect of water vapor in the atmosphere will be lessened, and our temperatures should plummet tonight.  Be prepared for lots of frost when you go out tomorrow morning--and some cooler areas away from water will drop into the teens.

This cool dry air will slowly warm, but expect sunny skies and cool nights for the rest of the week.

But the real worry is for the folks in California.  The cold air moving south has an Amazon Prime account and the delivery will be overnight.   By tomorrow morning, the cold, dense air and associated high pressure will have moved southward through Nevada, setting up a large pressure difference across the Sierra Nevada (see map below for 5 AM Wednesday).  This pattern will set up Diablo winds for northern CA and Santa Ana winds for southern CA, threatening both areas.


Southern California will face a real challenge with a powerful Santa Ana wind descending to the ocean by 5 AM Wednesday (see below).  The most severe winds (sustained 50 mph with gusts to 80 mph) will be east and north of downtown LA, but substantial winds will be felt southward down to San Diego. 
 The winds will weaken a bit by 5 PM Wednesday (see below), but will be more than strong enough to sustain any fires that started earlier.  It is crucial to turn off the power to a lot of folks in southern CA tomorrow. Turns out the Getty Fire was the result of trees on powerlines--just a taste of what is possible with the far more powerful winds overnight.


19 comments:

  1. Here in Central Washington this began on October 26th, huge North wind and a temperature drop. A week ago my wife flew from SeaTac to Phoenix in 2hrs 20mins because of the strong upper level North wind. Almost $150 knots.

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  2. Our buddy the triple R is back in town?

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  3. Apparently,a new all-time national (including AK) record low temperature for the month of October was this morning at Peter Sinks, UT. An astonishing -46F!

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  4. Surprised this morning to no frost on my very cold automobile (last driven at 5:15pm ). Was 31 deg outside in Lake Forest Park, but all the auto's in the area had crystal clear glass at 6:50am ( see what I did there, clear of crystals ).

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  5. With the dew point below 0F, I wouldn't expect to see frost (unless our temps drop below 10F or so, God forbid).

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  6. -2 in the Mono Basin here in the Easter Sierra. October cold record for the lower 48 shattered at Peter's Sink, Utah....-45.5!

    https://climate.usu.edu/PeterSinks/index.php

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    1. According to wikipedia, a temperature of -48F was recorded in Clear Water, AK during October 1975.

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  7. Cliff, I appreciate the Amazon Prime turn of phrase.

    Did you see that in central Wyoming, it got to -10F or lower overnight? In October? Unreal stuff.

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  8. Gov. Inslee's latest tweet says these fires are a result of climate change, implying that there would be no fires if man-made climate change wasn't occurring. Thoughts?

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    1. I grew up in CA and the threat of fire was the norm 20+ years ago. There will always be fires, but global warming may be exacerbating the problem by extending the dry period through the seasonal strong Santa Ana/Diablo winds.

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    2. What horsepuckey. These fires are the result of California's "environmentalists" having banned forest management beneath their power lines. We live in the Columbia Gorge less than a mile from a high-tension transmission line that I think runs from the nuke at Hanford.

      That line goes through forests that are thick around here. All of the trees beneath it, and to the sides, have long since been cut down. Oh yeah, but aren't we stupid out here in Eastern Washington?

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  9. The CA fires are so distressing, Cliff. I wonder how people living in dangerous areas will cope and adapt. Also, I'm curious to know if PC&E will take their lines underground. I suppose Seattle could have an influx of new residents from CA depending on how the fire issues are addressed.

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    1. It would cost $15,000 per customer to bury the lines. It might be a better idea for California's regulators to allow PG&E to maintain non-forested corridors under their transmission lines (as is the case here in the Columbia Gorge, where I live less than a mile from one such corridor) and aggressively trim around distribution networks.

      But no, the state's irresponsible "environmentalists" have blocked that, all while imposing a series of other mandates that have a) driven up electricity rates, and b) sapped funds needed for grid maintenance.

      If these power blackouts continue for another week or so, the next thing we'll be hearing about is widespread food shortages. I'm sure this will make "progressives" happy, because it will help their population control efforts by killing off the elderly and the disabled first.

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  10. There would still be fires. There always has been fires. People took it upon themselves to live in fire prone areas. Just like people took it upon themselves to live in flood prone areas. Thus the destruction is compounded. So on and so forth. What climate change influences is how dry the fuel is or how hard the winds blow for how long....

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  11. I agree with BAMCIS, above. Folks decided to live in these places due to ignorance. All kinds of businesses have been making lots of money from selling property to people in areas prone to fire and flood -with support from politicians. I've been following all this for many years. It's criminal and tragic.

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    1. We get it. You're a "progressive," and you want to crowd us into your cities so we can be preyed upon by your feral addicts, illegal aliens, and junkies. I'd rather die in a fire.

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    2. @twinkle

      I didn't move to the urban-wildland interface due to ignorance. It was to live with nature,a strong sense of community, way less crime,low population denstiy, low light and noise pollution and better air and water quality then large cities.

      Although we do get folks moving here that think its OK to Drive while they are websurfing or posting instagram pictures.

      Rural communities also have a strong sense of stewardship for the land that surrounds us.

      Hence my opposition to the habitat destruction carried out by the North Cascade Heli-skiing Corporation and why I favor the expansion of North Cascades National Park with them out of Wilderness quality terrain.

      Our Methow Valley community will benefit from the much needed economic impact from people seeking to enjoy a National Treasure. The North Cascade Mountains.

      Fire risk can be mitigated, just like some cities need to mitigate earthquake risk. Are those city people living in areas prone to earthquakes also "ignorant"?

      Chris H.
      Heli-free North Cascades

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  12. BAMCIS, that may be true to some extent, but these autumn fires are almost exclusively triggered by man-made causes: downed power lines, arson, cigarettes, sparks from chains dragging behind trucks. Lightning doesn't happen during Santa Ana winds (and is pretty rare outside of the Sierra in California) so there is no natural spark for these events. So while the coastal chaparral is indeed fire prone, most natural fires would happen during less windy times and would therefore be much less severe.

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