Unusual Cool Temperatures over the Pacific Northwest Leads to Strong Winds and Power Outages in California

Reposted from the Cliff Mass Weather Blog

Saturday brought record or near-record cold temperatures to the Pacific Northwest, and strangely enough, that led to unusual Diablo winds over northern California, with the regional utility PG&E cutting power to thousands to reduce the chance of another major wildfire.

Cold temperatures potentially producing wildfires?   Ironic, perhaps, but true.
Late last week an unusual slog of cold air, connected with an upper level trough, pushed into the Pacific Northwest, with the cool, dense air associated with high pressure at low levels.  That cold air/high pressure combo extended inland and then southeastward into the Intermountain West (from eastern Oregon down into Nevada).   And high pressure north and east of California resulted in strong, dry downslope, northerly to easterly flow that can produce dangerous wildfire conditions:  the feared Diablo winds.     Let  me illustrate this for you!
Below are a series of model forecasts during the period in question, including heights ( think pressure, solid lines), winds, and temperatures around 5000 ft (actually the 850 hPa pressure level).
At 5 AM Thursday, the cold air was starting to move in (bluish colors).


A day later (5AM Friday), the cold air was pushing inland.

Saturday morning at 5 AM, higher heights (and pressure) and cool air had extended into Oregon, with a very strong pressure (height) gradient over northern CA and Nevada.   Strong pressure gradients produce strong winds!

And by Sunday at 5 AM, the high pressure (and still cool air) pushed farther east and south, leaving a very strong pressure/height gradient across the Sierra Nevada and northern CA.  Lower heights and pressure are along the coast.  This is exactly the pattern that produces the dry, windy conditions called Diablo winds, that have been associated with major CA wildfires, such as the Nov. 2018 Camp and Oct. 2017 Wine Country fires.  No wonder PG&E decided to shut off the power in some communities.

In fact, winds did gust to 60 mph in some locations north of San Francisco (see below)

And over 45 mph gusts hit north and east of Paradise, CA, the location of the horrific Camp Fire last year.  With a poor power infrastructure, PG&E has to shut the power off to prevent their power lines from starting new fires.  One helpful thing this time of the year–vegetation is still relatively green, particularly after a very wet spring.

Having such strong Diablo winds is very unusual this time of the year, since normally these strong downslope winds avoid the summer.
Why?  Because they are driven by cold, inland high pressure that is rare during the summer.     To show this, here is a figure from a paper on Diablo winds written by UW grad student Brandon McClung and myself (I have a NSF grant to study Diablo winds, by the way).   Diablo winds on the western side of the Sierra Nevada are rare in mid-June and infrequent around the Bay Area.  Big increase in fall as cool air moves inland.

So why the unusual June Diablo winds this year?  Unusually cold temperatures.  Here is the climatological of temperatures at 850 hPa (again around 5000 ft) at Quillayute, on the Washington coast, versus time of the year.  The blue lines represent the record low temperatures for the date.  I put a marker on Friday’s value—pretty much tied the record low.  No wonder there was snow at the Paradise ranger station on Mt. Rainier on Friday and early Saturday!

But the temperatures were even more unusual in Oregon and vicinity.  This map, courtesy of NOAA, shows locations of record low maximum temperatures on Friday for that date.  LOTS of them over southern Oregon and Idaho.

And there were even some record low minimum temperatures for that date as well.

Even more impressive, there were some MONTHLY records for low maximum temperatures.  THAT is very unusual.

So the potential for major wildfires in CA is directly associated with colder than normal temperatures extending into the Pacific Northwest and into Nevada.  Even more interesting, global warming, which would probably reduce such cold-air periods, could well reduce the number of Diablo winds and thus wildfire threat periods like this event.   This is something I am researching using high resolution regional models run for a century. 

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June 10, 2019 2:10 pm

Cutting power to customers and getting a court ruling they can ignore PPA contract commitments for renewable power amounts to a good day for PG&E I guess.

Roger Knights
Reply to  ResourceGuy
June 11, 2019 2:28 am

“getting a court ruling they can ignore PPA contract commitments for renewable power”

Does anyone have more detail about this? I remember reading that power politics by the greens would force the contracts to be honored.

Reply to  ResourceGuy
June 11, 2019 11:11 am

Is this now to become “the new normal”? – – Shut off power to paying customers when “models show” something weather-ish might cause power surges, voltage spikes, transformer incidents, and potential fire initiation?

Could any of this ephemeral risk possibly be attributed to a bad mix of unreliable green electricity with sustainable fossil/nuclear-fueled base-load electricity? Or bad forest-management practices that restrict removal of tree/shrub fuel along transmission-line corridors?

California is leading the way toward 13th century lifestyles. Ain’t gonna turn out well

Larry in Texas
June 10, 2019 2:13 pm

“With a poor power infrastructure. . .”

THAT, my friends, and not unusually cold temperatures, or any kind of weather, for that matter, is the reason for the wildfires. Along with idiot-poor forest management.

But never blame human folly for your troubles whenever the weather presents an easier scapegoat.

Alan the Brit
Reply to  Larry in Texas
June 10, 2019 11:32 pm

Along with idiot-“rich” forest management.

There, corrected that for you! I’d suggest they have more than enough idiots it tow! 😉

E J Zuiderwijk
June 10, 2019 2:14 pm

Any chance that the ‘unusual cool temperatures’ will become the new normal?

Walter Sobchak
Reply to  E J Zuiderwijk
June 10, 2019 3:47 pm

Cool is just weather it is not climate. Hot is climate, not weather.

Reply to  E J Zuiderwijk
June 10, 2019 11:55 pm

until ‘usaul warm ‘ comes along , this afterall ‘heads you lose , tails I win ‘ sceince in action

George Fletcher
Reply to  knr
June 11, 2019 5:35 pm

Reading this on Tuesday, June 11, I am shocked at all the cool air I’m supposed to be experiencing! The temps will be near 100 today and tomorrow with a little cooling following, but for the foreseeable future, warmer than I’d like to experience in the heart of the Pacific NW [Salem, OR]. Nor have I seen the moisture related in the article. We are way low for rain here.

Tom Halla
June 10, 2019 2:15 pm

The cold air in the central West probably contributed to the very windy front that went through Texas yesterday, with straight line winds over 80mph in Dallas.

June 10, 2019 2:23 pm

Just don’t associate it with solar minimum conditions and they will let you be.

Ron Long
June 10, 2019 2:28 pm

Wow, this Global Warming deal is amazing! Sometimes it blows hot and sometimes it blows cold. Reminds me of the Aesops Fable: A snake was laying almost immobile in the snow when an old lady came along. She felt sorry for him, so picked him up and blew on him to warm him, and he gained strength and thanked the old lady. She then took him to her house for some food, and filled a bowl with hot soup for herself. When she started blowing on the soup, the snake asked her why, and she said it’s too hot and I am cooling it down. The snake then bit her and injected poison, and she collapsed. As she lay dying she asked the snake why he bit her as she had saved him. The snake replied “old lady first you blew warm air to warm me, then you blew cool air to cool your soup, only a Witch could blow both hot and cold, so I bit you, good riddance”.

I don’t intend this as an assault on any particular actual person but some of can speculate if you wish.

Reply to  Ron Long
June 10, 2019 4:52 pm

Motown does Aesop

June 10, 2019 2:40 pm

In Southern California these winds are common Oct-Feb. In Northern California they run a month earlier Sept-Jan, based on your graph..

Ewin Barnett
June 10, 2019 2:44 pm

Professor Valentina Zharkova: The Solar Magnet Field and the Terrestrial Climate


The key graphic of interest is at 30:20 or so. Also see about 39 minute mark. List of problems this causes at 44:16. I think her theory is more easily tested than others. Either we start in the direction her model indicates with the symptoms that her model indicates for several years in a row or we don’t.

Joe B
Reply to  Ewin Barnett
June 11, 2019 12:52 am

Starting to see references to Dr. Zharkova and her work almost every day now across a broad range of sites.
Awareness is spreading rapidly, apparently.

Reply to  Ewin Barnett
June 11, 2019 10:29 am

Solar Dipole from Wilcox Solar Observatory

Phil Salmon
June 10, 2019 2:50 pm

Swiss meteorologist Jorg Kachelmann slaps down the notion that wildfire risk is directly linked to high temperature:


Jorg: “Heat does not cause forest fires and is completely irrelevant. Forest fires are caused by the fact that it is dry longer, and then some fools – intentionally or not – throw something burning into the area, or park a very hot car over dry high grass and then drive away. The temperature on the day of the outbreak of forest fires does not matter.

Reply to  Phil Salmon
June 10, 2019 5:23 pm

The flashpoint of wood is given as 572°F (might vary with types of wood and a lot less for leaf litter) and fires are typically over 1400 F. I can’t see the ambient air being 104 instead of 100 making much difference.

Bill Murphy
Reply to  Robert B
June 10, 2019 9:27 pm

Dry wood also has a fairly high specific heat value. Twice that of concrete and about 40% that of water, so yes, a few degrees can make a difference. The difference between 45F and 104F is huge.

Richard Patton
Reply to  Robert B
June 11, 2019 11:58 am

Other than the fact that in the Western U.S. hot weather is usually accompanied by a very dry air mass. East of 100ºW longitude hot is usually accompanied by humid. Therefore Jorg Kachelmann’s observation is correct (for that area). For the Western U.S. hot almost always means dry. As to humans being the cause the majority of the time, tell that to the residents of Oregon, California, Washington, and British Columbia last year. The majority of the fires in that region (most were in BC despite the slanted reporting of the US media which made it seem as if all were in California) were cause by lightning.

Bill Murphy
Reply to  Phil Salmon
June 10, 2019 6:12 pm

Heat is not “completely irrelevant” but it’s not primary, either. The single biggest factor is fuel moisture content. (Try burning a green growing lawn at any temp and compare that with a pile of dead, dry grass.) The next two factors are RH (Humidity) and fuel density. RH is important because at very high values the fuels will not dry out and can even gain moisture from the air. Heat is important to the process because, for a given RH, the fuel will dry out faster when it’s hot, and therefore ignite more readily. And also, basic thermodynamics, when the air is warmer the fuel is also warmer and closer to ignition temp allowing the fire to spread more quickly because it requires less of the energy of the actively burning fuels to heat the fuel in front of the fire to ignition temp. Ask any experienced Western US wildland firefighter about “triple digit temps and single digit RH” and you’ll probably get a long story about some really scary fire one hot day in July. (Mine was July 4th, 1993 in Kingman, AZ. But never mind.)

J Mac
June 10, 2019 2:57 pm

It’s weather – deal with it.

Gary Pearse
Reply to  J Mac
June 11, 2019 7:58 am

JMac, and what about the rest of it that we want to throw away civilization for?

June 10, 2019 2:58 pm

Anything to do with CC causes forest fires. Everybody knows that.

Yeah that’s a /sa

Lawrence E Todd
June 10, 2019 3:01 pm

Do not worry, when we get finished massaging the data it will look like a heat wave

June 10, 2019 3:10 pm

Cold temperatures potentially producing wildfires? Ironic, perhaps, but true

It’s not ironic at all, wildfires are not related to temperatures but to drought and nothing other.

Reply to  Krishna Gans
June 10, 2019 4:42 pm

Fuel availability is the only thing partially related to drought. Management (or mismanagement) of the area also has a very large impact on fuel availability.

Wildfire incidence is related to availability of ignition sources (lightning, idiot, criminal arsonist, or… a high tension line vulnerable to high winds).

Spread of a wildfire is related to fuel availability, terrain, and weather (humidity or rain, and ambient – not fire generated – winds).

Robert W. Turner
Reply to  Writing Observer
June 10, 2019 5:47 pm

Not to mention the type of trees.

Reply to  Krishna Gans
June 10, 2019 10:01 pm

Drought might lead to larger fires but my understanding is that small diameter litter can become dry enough to easily catch fire and bur rapidly within hours under good sun and a brisk dry wind, even after a good rain the night before.
Evidence to the contrary?

Gary Pearse
June 10, 2019 3:28 pm

Here in the northeast in Ontario-Quebec and the east coast, we had our first “summer” wearher for a couple of days -not much above 20C (68F) a good 10F below seasonal. Hey we’re only a dozen days to the longest day. In past weeks, the heat has been on. I usually turn it off by May and suffer a few cold days. Egad what is it going to take to change so many minds about Catastrophic A Global Warming.

john harmsworth
Reply to  Gary Pearse
June 10, 2019 4:21 pm

0C overnight here in Saskatchewan with a touch of frost in some low lying areas. Very unusual for this far into June. No apparent damage but it’s so dry here anyway as we are into our third year of drought that it will be a miracle to get any decent crops now anyway.

Reply to  john harmsworth
June 10, 2019 5:20 pm

Here in the Edmonton area of Alberta it had been cold and wet for four or five days, with temperatures not even able to make it up to 15 degrees C and getting down to just above freezing at night. Today is the first day that it seems to be returning to more normal summer time temperatures.

June 10, 2019 3:56 pm

I wonder how well the solar panels and wind turbines held up in the wild weather.
Resilient and reliable?

June 10, 2019 5:02 pm

We’re in a mild El Nino. link yes/no?

Among other things, El Ninos are supposed to cause rain in California. link yes/no?

This is very strange weather for an El Nino. yes/no?

Where I am, in the vicinity of the lower Great Lakes, people are beginning to wonder if we’re going to have a summer.

Robert W. Turner
June 10, 2019 5:43 pm

Unusually cool in the center of NA too. For the past two days it has felt like fall due to a brisk north wind.

Jeff Alberts
June 10, 2019 6:01 pm

I live on Whidbey Island, well into the blue portion of that first map. Didn’t seem unusually cool this weekend to me. And considering that July 4th around here usually 60 and damp, I don’t buy “unusually cold” on this article.

Reply to  Jeff Alberts
June 10, 2019 9:11 pm

The temperatures dropped quite a bit the more inland you went. Right on the coast, especially close to tide water, there was a bit of moderation. From Texas (where that crane in Dallas blew over in high winds) to the Cdn prairies, it was much colder than average causing a lot of funky weather. Definitely was on the cold side for this time of year over a very large area, but not totally unusual either. It is just weather. I have seen it snow every month of the year in western Canada or northern USA, although usually above 3,000 feet elevation. Nothing really much surprises me anymore.

Jeff Alberts
Reply to  Earthling2
June 19, 2019 5:59 pm

Like I said, I’m smack dab in the middle of the blue area, assuming that’s the coldest, and not a political map, and it wasn’t unusually cold.

June 10, 2019 7:54 pm

Tell you one thing that was “twice-in-a-lifetime” (for this old Goat), and that was last evening, sitting on the deck, facing Castro Valley in the Hayward Highlands (Bay Area, California).

Noctilucent Clouds aplenty! A rather striking and remarkable display. At first, I thought they simply were very high cirrus (to the North) backlit by reflections off the Pacific Ocean or something. But no. As I watched over about an hour, they got brighter and more electric blue-white against the darkening dusk sky. The cirrus were going one way, and they a different direction. Very slowly.

Reading up on it, apparently “June thru July in the latitudes above 40°” is the normal viewing season. Maybe so. The only time I remember seeing them before was in 1978, camping, with a couple of college buddies, up in the Canadian Cascades.

What was particularly striking about last night’s display was the fact that they weren’t at all “streaky” in the way often photographed. Instead, they were “crazily mottled and turbulent”. Not moving, not in motion, just as if that was how they froze in the upper atmosphere. Very striking. My idiot smart phone couldn’t take a picture in the reduced light.

Does it portend anything?

Dunno. Unusually low temperatures in the north.
Very unusual cirrus configurations yesterday, looking like they had trails going UP…
Perhaps injecting water vapor into the Mesosphere?
Who knows.

Just saying,
GoatGuy ✓

Reply to  GoatGuy
June 12, 2019 7:14 am

http://www.drroyspencer.com/2019/06/electric-blue-night-clouds-are-invading-the-u-s/ says in part:

In the late spring every year, people at far northern latitudes have often seen these on clear or partly-cloudy evenings. But solar-minimum conditions, with few if any sunspots, are causing cooling in the extreme upper atmosphere around 80 km (~50 miles) high where the lowest atmospheric temperatures are recorded, approaching -150 deg. F (-100 deg. C). That altitude is above 99.999% of the air in the atmosphere.

Adding to the spectacular electric blue displays is increasing atmospheric methane, which gets converted to water vapor at these altitudes, and increasing atmospheric carbon dioxide, which causes enhanced cooling of the upper atmosphere. The result is that the conditions necessary for NLC formation are extending farther south than ever before.

Richard Patton
Reply to  Ric Werme
June 12, 2019 10:38 am

Please refrain from custom acronyms that no one else knows. NLC for (I’m assuming) noctilucent clouds, doesn’t even come up in a Google search.

John F. Hultquist
June 10, 2019 8:56 pm

I was on the Gold Creek Trail (3 miles NNE or Snoqualmie Pass) Friday morning, with a freshly snow covered Rampart Ridge and Alta Mountain to our east. That’s not unheard of but near the Creek it was 40°F with showers. That was unusually unpleasant.
The neat thing was that we could leave. Can’t help you with living on Whidbey Island, though.
– – winking smiley face – –
Poe’s Law

Stephen Richards
June 11, 2019 1:55 am

NW Europe having very cold and wet june, WEATHER. second june like this in 10 years.

June 11, 2019 3:26 am

Stratospheric intrusion in the northwest US.

June 11, 2019 3:31 am

Now the cold air area is moving east.

June 11, 2019 7:19 am

The temperature in the Central Pacific drops again. A strong jetstream in the south will not allow the development of El Niño.
comment image

Reply to  ren
June 11, 2019 12:32 pm

ren …here is a thought which I had at the end of March which may explain why a La Nina has yet to develop at this point in the ongoing solar minimum. … https://www.facebook.com/groups/682610291864519/permalink/1968097849982417/

“…In my last post on my solar/MEI correlation I puzzled over the lack of a La Nina developing at this point of the ongoing minimum. I then proposed two possibilities. Here was the first “Here are several possible reasons for that. First, is this truly the beginning of a Gleissberg or solar grand minimum? Would either of these cyclical solar events forestall a La Nina during the minimum?”.

Then Mal MacDonald questioned my thoughts which made me question “What am I missing?”. Thanks much Mal. Here is the answer. I have the full ENSO record from Hadley which goes back to 1870, and guess what that shows? There are two solar cycles which are similar to what is now occurring and they both happened during the last Gleissberg Cycle in the early 1900s.

Specifically, they are SC 14 and SC15, Jan 1902 and July 1913. This imo, verifies that we are actually in the next Gleissberg right now, and potentially a GSM not too far away. This also gives rise to a brand new thought/potential understanding of what constitutes a solar grand minimum. I’ll leave that to later. My thoughts are on fire. As often happens to me in the spring of every year.

Every other solar minimum in the last 150 years has a La Nina except for those 2, and this current minimum, … https://en.wikipedia.org/wiki/List_of_solar_cycles. ..”

Reply to  goldminor
June 11, 2019 2:24 pm
Reply to  ren
June 11, 2019 4:57 pm

I have been watching the South Pole atmospheric layers with great interest since earlier this year. There was a sudden shift which led to a rapid drop in temps back around mid March which surprised me. Since then the cold spot at 10 hPa then continued to drop down to a low of -119 F. Not sure how that compares to any typical year as I have not been watching this area long enough. Recently this has led to surface temps reaching close to -90 F.

The North Pole atmospherics also has an unusual feature this year at 70 hPa. For some reason wind speed at that level quieted down to almost nothing. Yet both above and below that height wind speeds carry on as usual except for the pattern of the wind flow. It appears to me as if a change is afoot. I would guess that this is a direct consequence of the current solar conditions which are influencing changes to wind patterns.

Mark Albright
June 11, 2019 7:24 am

The cold air reached Oklahoma yesterday (10 June 2019) with a historically cold temperature reported in Oklahoma:

Reply to  Mark Albright
June 11, 2019 9:18 am

Look at the satellite. You can see the jet stream from the north.

Steve Z
June 11, 2019 12:11 pm

The unusually cold weather in Oregon and southern Idaho spread into northern Utah over the weekend. Lows around 40 in Salt Lake City, in the 20’s in the mountains. Long-term average high for Salt Lake City in June is 81 degrees, low 60 degrees.

This cold front was dry, but May was unusually cold and wet this year, with over 4 inches of rain. If there’s any “global” warming going on somewhere, it’s not here.

Reply to  Steve Z
June 11, 2019 7:51 pm

Not yet June 22.
Is this a late cold front from last winter?
Or an early cold front from next winter?

/glaciers expanding

June 11, 2019 4:09 pm

I think it’s time to compare 2019 to 2009 with solar minimum effects on cold fronts in NH summer.

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