Sunday, August 25, 2019

Near 100F in Portland But Low to Mid 80s in Seattle. Why?

The contrast in weather between Portland and Seattle, only 145 miles apart, will be substantial the next few days, with Portland approaching the century mark, while Seattle only warms into the lower 80sF.

Why does this happen?   To understand, one has to know about a crucial local weather feature, the thermal trough, and the impacts of terrain and land/water contrasts.  And it will also explain why it will get quite breezy in Seattle on Tuesday, with strong winds from the north.

Let's start with the latest forecast from the excellent system:

On Tuesday, Seattle is predicted to get to 80F, while Portland hits 97F.   Quite a contrast.  Byt why?

Let's start by looking at the latest surface air temperature forecast from the UW high-resolution WRF simulations.   At 5 PM Monday, it is warmer in the Willamette Valley  (80s), then Puget Sound (70s)

But then the heater is turned on within the Willamette Valley with temperatures rising into the upper 90s on Tuesday, even above 100F around Medford.   But way cooler over Puget Sound and almost chilly in NW Washington.

The key large scale feature that develops on Tuesday is an upper level ridge building over the region from the Southwest (see 500hPa--about 18,000 ft-- map at 5 PM Tuesday).

This feature is associated with increasing sea level pressure to the east of the Oregon/Washington Cascades and easterly (and thus offshore) flow across the Cascades. 

The sea level pressure map for 5 PM Monday below shows high pressure offshore that is canting into eastern Washington.  Temperature at 2 meters is indicated by the colors, with brown and red being the warmest air. You can see an area of low pressure over northern California that is associated with warm temperatures...this is the thermal trough and is associated with easterly flow descending down he Sierra Nevada and Cascade ranges.  Notice how this feature produces a large north-south pressure difference over the Willamette Valley and southwest Washington, with higher pressure to the north.  This pressure difference will accelerates the air towards the south (northerly flow).

 By Tuesday afternoon, the easterly flow across the Cascades will strength the thermal trough in the Willamette Valley causing the northerly flow to accelerate over western Washington and warming the Puget Sound region. This northerly flow will bring in cooler air from off the Georgia Strait and Strait of Juan de Fuca into western Washington, preventing Puget Sound from heating up like the Willamette Valley.

Expect the winds to get gusty in Puget Sound on Tuesday.  The wind gust forecast for 2 PM on Tuesday shows wind gusts hitting 25-30 knots from Seattle to Tacoma.   Get your sailboat ready!

So expect blustery/warm (low 80s) condition around Puget Sound on should wonderful to experience--while Portland and the Willamette Valley will be toasty. 

This heat wave won't last.  Wednesday will remain warm, but then marine air will push in on Thursday and seasonal temperatures will return.  And there is no expectation of lightning during the next few days, so I would not expect any high-terrain fires to accompany this short heat wave.  But human caused fires could occur in western Oregon if folks are not careful.

Announcement:  I will be giving a talk "The Great Storms of the Pacific Coast" in Ocean Shores at 6:30 PM on September 7th at the Shilo Inn as part of the Coastal Interpretative Center's summer lecture series.  More information is found here:   Shilo Inn is offering special room rates for those wishing to stay overnight, as well as a special buffet.   

Friday, August 23, 2019

Is Western Washington Really in Severe Drought?

For society to make good decisions on environmental matters, decision makers inside and outside of government require accurate and realistic guidance.  For that reason, I am a bit worried that there is a problem with a frequently cited source of information about drought across the U.S.:  the U.S. Drought Monitor website.

The latest release of this information suggests that Washington State is one of the most drought-affected locations of the U.S., with much of western Washington in severe drought.

Below is an expanded version of the graphic for just Washington State.  Severe drought along the coast, much of SW Washington and the western slopes of the northern WA Cascades.  Moderate drought over more than half the state.

Now is it reasonable to suggest that much of our state is in moderate to severe drought?   Severe drought sounds quite scary to me and one would expect extremely serious problems as a result.

Let us begin by looking at the difference from normal of precipitation for the summer so far. Most of the Northwest  has been near normal, including the supposed "severe drought" area.

Current streamflow?  Most sites are near normal (green colors).  A large number are above normal (cyan and dark blue), a similar number are below normal (orange and red).

Wildfires are below normal across the State this year, as is smoke. 

What about water resources?  All the major urban areas have plenty of water, without any drought restrictions.  Seattle's reservoirs are slightly below normal, with no water issues (see below).

The only water resource issues are on the Olympic Peninsula, where Port Angeles and few small water districts are asking for voluntary reductions in water usage.  I could find no impacts on agriculture or any other industry due to the "drought."

The origin of the drought declaration is from the relatively dry winter we had last year, something illustrated by the figure below, which shows the difference from normal of the total precipitation since October 1, 2018. Southeast Washington was wetter than normal, but the coastal zone and the western Cascade slopes were drier than normal.   But having a location that normally gets 100 inches a year, now receive 80 inches, is a far cry from a severe drought and the impacts are very modest at best.   And a dry winter was supplanted by a normal summer even in those parts.

Another way to appreciate this year's precipitation situation is to view the cumulative precipitation over the past year   For Seattle, we ended up with about 80% of normal precipitation (see below, normal is cyan, observed is purple)
And the situation is similar at Quillayute, on the northern Olympic Peninsula coast.
80% of normal precipitation does not represent an extreme drought and has occurred many times during the past 50 years.

My own opinion is that the term severe drought is not appropriate for the kind of situation observed in western Washington this summer--- one with few impacts and not that unusual.  Using such strong terminology makes it harder to get folks to react when a real severe drought occurs and doesn't accurately communicate the actual threat level.   And some politicians use such overly exuberant language to push their agendas. 

This is the kind of year that "abnormally dry" might be appropriate and the "D word" might not be the best choice.  Extreme drought seems over the top.

Severe drought

Wednesday, August 21, 2019

Why you can't trust your eyes

You watch a nice sunset.  You see the sun crossing the horizon and believe your eyes.

But strangely enough, at the moment you thought the sun had set, it had already set several minutes. ago.

What you experienced was an atmospheric mirage, and there are a lot more like this one.

The trouble is that we are trained to believe our eyes.  And we assume that light moves in a straight line.  That an object is where it appears to be.

But that is often not true, particularly when the atmosphere acts as a lens and causes light to bend.

Light is influenced by our atmosphere.  Where the atmosphere is dense, light slows down.  When it the atmosphere is less dense, the speed of light is faster.  And when light moves between layers of different air density, the direction of the light can change or bend.  You have seen such effect with pencils in water (see below)--now consider what happens at sunset.

The atmosphere is denser near the surface and less dense aloft.  The causes a lens effect that results in objects looking higher than they actually are--something known as a superior mirage.   The figure below shows the situation.  The apparent position of the sun...what it looks like to above the horizon.  The real position is below the horizon...the sun has already set.

The sun is not the only object that isn't where you think it is.  The stars, particularly near the horizon, are also shifted upwards by the lens effects of the atmosphere.  And this superior mirage effect can be seen locally as well when warm air passes over cool Northwest waters.   For example, cliffs on the opposite side of the sound can be elevated into sky as impressive walls of land (see example below).

So the moral of the story is don't always believe your eyes, reality can be different.    Same thing for what you hear.....but that topic belongs in another blog. 😃

Monday, August 19, 2019

Snow in northern BC, Rain in the Northwest

The fire season is over in northern BC.     Done.  Finished. Currently, it is SNOWING  up there, with all kinds of warnings and dangerous roads (see below).  And this is after quite a wet period recently.   What a difference a year makes!

The latest infrared satellite imagery is scary for this time of the year (see below).   A range of potent weather systems are lined up offshore, ready to move in on us.  Of particular note is the tightly wound cyclone offshore of southern Oregon.   Doesn't look like a mid-August satellite pic.

Tuesday is the last dry day for our region for a few days. The 24h total precipitation ending 5 AM Wednesday show the effects of a potent frontal system, with lots of rain on our coast and Vancouver Island.  Forget the catastrophic fire/drought warnings for that region.  Way too moist now.

During the next 24 h, the rain moves inland, with western WA getting a good wetting.  Even rain in eastern WA.  The last wildfire (Williams Flats on the Colville reservation is 87% contained and will further decline with this rain.

The action on Wednesday will be associated with a strong upper level trough moving through (see map for 8 PM Tuesday below).

And then as advertised, the flow configuration changes and a strong upper level jet moves right across the Pacific into our region (see winds speeds at 300 hPa....about 30,000 ft) for 5 PM Friday, shown below.  Some flights will use this wind field to head directly across the Pacific.

Enjoy the rain.   Our gardens will be happy.

Saturday, August 17, 2019

The First Autumn Storm Makes Landfall on Wednesday

It is very typical for first "autumn-like" storm to reach our region during the third week of August....and this year will not be an exception.  In fact, we have two systems that will be making landfall this week, with the first one being the strongest.

You can see the impact of this "first autumn storm" in the precipitation climatology Seattle.  Below is the  daily  climatological probability of enjoying at least .01 inches at Sea-Tac.  At the end of August the probability jumps to roughly 25%! 

Rain comes in on Wednesday, associated with a robust Pacific front, with the 24 hr total ending 5 PM Wednesday being substantial over the Olympic Peninsula and north Cascades.  On the coast, some locations could get several inches.

The Wednesday system is associated with a front connected with a very intense low center moving into southeast Alaska (see surface weather map at 2 AM Wednesday). Let's say that some of the Alaska cruises will be enjoying some rock and roll that has nothing to do with music.

Another system comes in late Friday and Saturday, with substantial amounts shown in the 24h total ending 5 AM Saturday.

All this rain will be associated with a massive reconfiguration of the atmosphere to a more fall-like pattern.  To illustrate, here is the upper level map for around 30,000 ft ASL, showing the jet stream winds in colors.   At 2 PM today, there is a ridge (higher pressure and heights) stretching from the Aleutians to California, and the jet stream (yellows and light green colors) is to our north.

But by 11 PM next Saturday everything is different, with a fairly strong jet stream heading right into our region.   You won't have to worry about smoke in the Northwest.  You will have to worry about finding your umbrella.

This pattern change will have a huge impact on wildfire potential, greatly reducing the changes of new fire initiation or the growth of old, smoldering burns.

Thursday, August 15, 2019

Where are the best summer breezes in Seattle?

It is warm night.  Your home or apartment is kind of stuffy.   You are looking for a park or outdoor area with a cool, refreshing breeze.

Where do you go?

This blog will provide some guidance based on years of searching for that special breeze and exploration of the regions weather.

Number One.  The Kite Hill of Magnuson Park in NE Seattle.

It doesn't get any better than this.  The Kite Hill is an artificial "peak" perhaps 150 ft high, on a peninsula sticking out into Lake Washington.   Cool breezes are channelled north-south down Lake Washington, as part of the regional wind feature called the Sound Breeze.  The Sound Breeze develops each afternoon and is really a regional sea breeze between the land areas of Puget Sound and the cool water of the Strait of Juan de Fuca and the Pacific Ocean.

The Magnuson Kite hill has excellent exposure from several directions, allowing unimpeded breezes, and the views of the Cascades, Lake Washington, and Mount Rainier are exceptional.

How strong are the winds there?  There is no anemometer at the top of the hill, but there is one at Sand Point Sail, a short distance away and located near the water.  Here are the winds for the past week.... most afternoons get to around 11 mph, some as much as 15 mph.  Not too strong, not too weak.  Perfect.

So for consistent summer breezes plus view, Magnuson Kite Hill is number one.

Number Two:  Discovery Park

Discovery Park shares important attribute with Discovery Park:  it is located on a peninsula sticking out into cool waters, with much of the park at some elevation.  Plus magnificent views.    But it does have a feature that can I say this delicately?....provide the breezes with some aroma.

There are two main breeze venues in the Park.  One is near sea level down by West Point, at whose tip there is a Coast Guard station.  Temperatures are almost always cool there and winds are reliable, particularly in the late afternoon (from the aforementioned  Sound Breeze).  The winds at West Point Light House (below) demonstrates this, with winds of 10-12 knots.  And during stormy periods, the place is just howling.

But West Point has an issue--a massive sewer treatment plant that can make the breeze a bit potent. And it is quite a walk to West Point.

The other location is up on the bluffs--good exposure to southerly winds and a grant view.  But summer northerlies can have difficulty reaching that location.

Number 3:  The Northwest Coastal Parks:  Shilshoe, Carkeek and Richmond Beach

These locations on the NW Shoreline of Seattle (and Shoreline)  don't offer much elevation, but have decent exposure to northerly flow on the shore, but can rapidly warm a hundred or so feet inland.

A location near Carkeek Park (northern star in figure) has sustained winds reaching around 5 mph, with higher gusts.  Not quite the same breeze as the first two locations I noted.
There are, of course, some decent locations south of of downtown (Alki, Lincoln Park, Seward Park).  Alki can get a good summer breeze (but less than the northern locations), and even less so for Lincoln and Seward.   A plot of Alki Beach winds for the last week are shown below.
Anyway, this is the season for evening northerly breezes in central Puget Sound...enjoy them.  One of the jewels of living around here.

Tuesday, August 13, 2019

Smoke: what a difference a year makes.

We are now in primo smoke season for the Pacific Northwest and our skies are nearly smoke free.   To illustrate the point, here is today's high resolution MODIS visible imagery (top) and the same image one year ago (bottom).

What a difference. 

The air quality map for the region, shows green colors at nearly every location (green means good air quality).  Last year the map was full of yellows and reds.

Remember the smoke from Alaska a week ago?   None of that anymore, as shown by the small particle concentration at Seattle (see below)
This lack of fires is particularly impressive considering how much lightning we had over the weekend--I mean many thousands of strikes, mainly east of the Cascade crest. 

For example, below are the strikes for Friday, Saturday, and Sunday.  Thank a relatively moist summer, generally mild temperatures, and the active suppression activities of WA DRN, OR ODF, US Forest Service, and others.   And remember the suppressing fires has issues--fire is a natural part of the east-side landscape.

No heat waves in our immediate future, so the fire/smoke situation should stay in check.

Monday, August 12, 2019

Is Global Warming an Existential Threat? Probably Not, But Still a Serious Issue.

During the recent presidential debate, a number of candidates suggested that global warming represents an existential threat to mankind, and thus requires dramatic and immediate action.

Governor Jay Inslee has been particularly generous in the use of this term, but he is not alone.  Kamala Harris, Cory Booker, Bernie Sanders and Elizabeth Warren have said the same thing, as have several media outlets and environmental interest groups.

Some of these folks also claim that the window for action on climate change is closing--Jay Inslee suggests that the next president will be the last able to take effective steps.  Others suggest 10 or 12 years.

But are these existential threat claims true?  That is what we will examine in this blog.

An existential threat is one that threatens the very existence of mankind.    Something that is a simply a challenge or an inconvenience is not an existential threat. An existential threat must have the potential to undermine the very viability of human civilization.

As described below, global warming is a serious problem and its impacts will be substantial---but in no way does it seriously threaten our species or human civilization.  And with reasonable mitigation and adaptation,  mankind will continue to move forward---reducing poverty, living healthier lives, and stabilizing our population.

What do current climate models tell us?  These models are run under specific scenarios of emission of CO2 and other greenhouse gases (see figure).   In one, RCP8.5, we simply continue doing what we are doing, with escalating use of coal and oil.  Not much renewable energy.    Many believe this scenario is too pessimistic.  Much more reasonable is RCP 4.5, which has modestly increased emissions through 2040, declining after 2050.  I suspect this one will be closer to reality.

The implication of these emissions on global temperature is shown below based on a collection of climate models (CMIP-5).  Under the extreme scenario, the earth warms by about 4C, but for the reasonable one (RCP4.5), global warming is about 2C (3.6F).  This warming will not be uniform, being greater in the polar regions, less over the eastern oceans.

You will note the temperature rise in RCP 4.5 is relatively steady through around 2045 and then starts to gradually plateau out.  No sharp transitions, no falling off of a cliff, no sudden catastrophes. 

I have run a large collection of high resolution climate simulations over the Northwest, driven by the aggressive RCP 8.5 scenario.   As shown for Seattle's mean annual temperature below, there is a steady rise, again with no sudden changes that would be hard to adapt to.    Most NW folks will want to purchase an air conditioner for summer, but there is no threat to our existence, and winters will be more pleasant.

But what do official international and national evaluations project for the economic future?

First, let's check the conclusions of the highly respect Intergovernmental Panel on Climate Change (IPCC), which  provides a consensus view of many scientists and nations. Their analysis (SR15, Chapter 3) quoted a paper by Yohe (2017) that found a U.S. GDP loss of 1.2% per degree of warming,   So with a 2 C global warming associated with RCP4.5,  we are talking about a 2.4% loss of national income in 2100.  Not a 2.4% loss from today's levels, but 2.4% less of the substantially greater income in 2100.

What about the recently released Fourth National Climate Assessment, a document heavily cited by the U.S. environmental community?  Their analysis is that the damage to the U.S. economy in 2100 would be about a 1% loss (see below)  This is not a 1% loss from the current U.S. gross domestic product (GDP), but a 1% loss of the substantially great GDP in 2100.    We will be much richer in 2100,  and will lose 1 % of our GDP  because of global warming.  Doesn't sound like the end of civilization, does it?

W. D. Nordhaus, who won a Nobel Prize in economics for his study of the economic impacts of climate change, examined a large number of studies regarding the impacts of global warming on the world's economy (see below).  He and his co-author (A Moffat) found that a 2C increase in global temperatures would result in 0-1% damage to the world economy in 2100. Doubling the warming would only increase the damage to around 3%.  Again, no existential threat.

Reading these numbers and considering the many reports backing them up, there clearly is no existential threat to either the U.S. or mankind from global warming, leaving one to wonder why are so many politicians, environmental activists, and lots of media are spreading this existential threat line.

And the above studies are not really considering the potential for major technical breakthroughs in energy generation (e.g., fusion), renewables energy sources, or carbon removal form the atmosphere (sequestration).   I believe that such advances are inevitable, just as no one in 1950 expected that 2000 would bring personal computers, cell phones, and more.

 You also have to wonder whether scientists, politicians, and environmental folks really believe the existential threat warnings they throw around.   Many talk the talk, but most don't walk the walk.

Presidential candidates with little chance of securing the nomination are flying back and forth around the country, resulting in enormous carbon footprints.   Climate scientists fly more for work and pleasure than anyone.   Many environmentalists oppose nuclear power, one of the technologies that could produce massive carbon-free energy.  And several local Washington State environmental groups opposed a revenue-neutral, bipartisan carbon tax initiative (I-732).

Global warming is a real issue and we are going to slowly warm our planet, resulting in substantial impacts (like less snowpack in the Cascades, increased river flooding in November, drier conditions in the subtropics, loss of Arctic sea ice).    But the world will be a much richer place in 2100 and mankind will find ways to adapt to many of the changes.   And there is a good chance we will develop the technologies to reverse the increasing trend in greenhouse gases and eventually bring CO2 concentrations down to previous levels.

Global warming does not offer an existential threat to mankind, and politicians and decision makers only undermine their credibility and make effective action less likely by their hype and exaggeration.  And their unfounded claims of future catastrophe prevents broad national consensus and hurts vulnerable people who are made anxious and fearful. And just as bad, all this end of the world talk results in folks turning away from the issue, both out of fear and from intuition that a lot of hype is going on.