January 24, 2022

Air Quality Declines As Inversion Slowly Weakens Overhead

 Inversions, in which temperatures INCREASE with elevation,  suppress vertical mixing, which in turn allows pollutant concentrations to increase near the surface.

And with a strong inversion over western Washington and Oregon the last few days, air quality has degraded to moderate levels at several locations.  

To illustrate, below is a map  (at 7 PM today) showing the concentrations of small particles (less than 2.5 millionths of a meter) that are capable of passing deep into your lungs. Nasty stuff.

 Low concentrations are green, with moderate values in yellow and orange, and red being even higher.  The Puget Sound region has degraded air quality and it is even worse around Portland.  Generally good in the mountains.


Graphic provided by PurpleAir

You can see the declining trend of air quality in Seattle with a plot of the small particle concentration during the past few days (below).  A progressive upward trend in small particles.


The sources of the particles include combustion from heating, burning of gas and diesel fuels in cars, and from burning wood in fireplaces and wood stoves.

During most winter days, these emissions are little problem around here, with stormy, wind conditions and an atmosphere that facilitates vigorous vertical mixing of air in the lower atmosphere.

But during the last three days, high pressure aloft has produced a well-defined inversion, as noted in the vertical sounding at Quillayute this morning at 4 AM. (Quillayute is on the northern WA coast)--see below.  Red is temperature, the x-axis indicates temperature (°C) and the y axis is height in pressure (700 is about 10,000 ft) 

You can think of an inversion as a meteorological barrier to air motion.  Here is a beautiful example of what happens when smoke hits a low-level inversion (see below).... it is like hitting an invisible barrier.

Image by S/V Moonrise

The particle concentrations we experienced the last few days are NOTHING compared to what we breathed during wildfire events, something shown by the plot of small particle concentrations from summer 2017 to now (see below).   September 2020 was the big "winner" with values about ten times higher than what we experienced today.


The good news is that our winter concentrations are getting lower and lower, as fewer homes burn wood (very dirty), cars and trucks get cleaner, electric cars become more numerous, and with effective burn bans and other restrictions by air quality groups like the Puget Sound Clean Air Agency.

And some other good news...the inversion is weakening and will probably break later today--maybe even with a glimpse of the sun.  And stormier conditions will return on Friday.

Prepare to take a deep, healthful breath!



January 23, 2022

The Southern Oregon Coast Hits 79F as a Super-Inversion Develops over the Northwest

Update at the end!

High pressure and a super-inversion have developed over the Northwest, and jaw-dropping weather contrasts have developed--both in the horizontal and the vertical.

For example, yesterday (Saturday) temperatures zoomed up to near 80F on the southern Oregon coast, with 79F at Brookings, Oregon (see yesterday's max temps, below, click on the image to expand).  The forecasts were right.


At the same time, temperatures were in the 40s in eastern Oregon and BELOW FREEZING in large sections of the Columbia Basin of Washington (see Saturday's high temps below). 

If you were in frigid, sub-freezing Wenatchee yesterday and wanted to warm up by 20F you could do it--by going up into the mountains.  


This morning, the Puget Sound lowlands are enshrouded in fog, but clear skies are only about 1000 feet above.  

Want proof?  Here is a picture from around 1200 ft in Bellevue, looking west, provided by Dr. Peter Benda.  Fog covers the lowlands, but blue skies are aloft.


Or this picture from the top of West Tiger 3 (2500 ft) by 
Dr. Steve Cobert.  Cougar Mountain is an island in a sea of fog and low clouds.


The pattern is confirmed by the visible satellite image at 8:16 AM this morning (below), with the western lowlands enshrouded by fog, as is the Columbia Basin.  But the coast is clear.


The origin of these sharp contrasts is strong high pressure, which has produced a super-inversion over the region.

The upper level (500 hPa, about 18,000 ft) for yesterday at 4 PM (shown below) clearly indicates a strong ridge of high pressure just offshore.   And just east of such ridges, very strong sinking occurs.


Such sinking produces what is known as a subsidence inversion.   An inversion is when temperatures INCREASE with height over some layer of the atmosphere, which is the inversion (opposite) of what normally occurs:  temperature decreasing with height.  

Why do high-pressure areas create inversions you ask?  

 Because sinking air is compressed and warmed.  The sinking is larger aloft but weakens towards the surface (because the ground is in the way!).    Also the clear skies aloft air enable radiational cooling from the surface before any fog forms.

Let me show you how impressive the inversion was this morning.  The radiosonde-based vertical sounding at Quilayute shows warming of about 18C (roughly 32F) in the lower few thousand feet (see below).  WOW.

And aircraft coming into and out of SeaTac airport measure temperatures, and this morning at 8 AM temperatures increases from the lower 30s near the surface to the 50s above 2000 ft.  Double wow.

Image from Seattle SnowWatch, funded by the City of Seattle

Hike to the top of Tiger Mountain today (at about 2500 ft) and you can have your lunch in bright sun and perhaps 60F, with your hike starting near freezing.  My kind of hike.

High pressure will be hanging around through Thursday, after which precipitation will return to the Northwest.  It has been a nice break from the rain, providing a chance for things to dry out a bit and lessening the chances for landslides and slope failures after a very wet period.
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Important Update at 3:43 PM

With a strong inversion, there was a huge difference between the temperatures at Tiger Mountain Family Nudist Park --37F-- (elevation 646 ft) and Poo-Poo Point (about 1550 ft) -55F (see map below).   In fact, Poo Poo Point, which is known for hang gliding,  peaked at 57F.

So roughly 20F higher about 900 ft up.  A very strong inversion.

I suspect the Nudist colony folks may be moving up the hill to Poo Poo Point today for obvious reasons.  Stay tuned, this could get interesting!  







January 21, 2022

High Pressure's Two-Edged Sword: Heat and Cold Fog. Plus the Weekend Forecast in My New Podcast

 High pressure has built over the region and will strengthen on Saturday (see surface map for 4 AM Saturday morning).


Strangely enough, high pressure during the winter can have two localized impacts on our region:  cool, foggy conditions in the western lowlands, OR very warm, sunny conditions where downslope flow is forced by regional terrain.

Such will be the situation this weekend, where northern Puget Sound will be dank, cloudy and cool, while the Oregon coast (and to some degree the southern WA coast) will enjoy sun and warmth.  The Columbia Basin will also be caught in the murk and cold.

To illustrate the wildly varying situation, here is the forecast surface air temperature for 1 PM Sunday.  Some places on the Oregon coast will get into the lower 70s, while Puget Sound will be in the lower to mid-40s.  BELOW FREEZING in the Columbia Basin.  Quite nice on the Long Beach Peninsula.  COLD over Northwest Washington.

Want to know why such extremes occur over our region during high-pressure situations?  

Or get more details about the forecast?  Check out my podcast--either with the link below or through your favorite service.


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January 19, 2022

"Code Red" on the Oregon Coast

 Don't worry,  this time code red is a good thing.

Below is the latest high-resolution surface temperature forecast for Saturday at 4 PM.  Red colors are temperatures above 60F along the Oregon coast!    The kind of code red I like.  And near Brookings, just north of the Oregon/CA border temperatures surge into the mid-to-upper 60s.


On Sunday, the code red temperatures are even more extensive along the coast as well as extending along the western slopes of the Oregon Cascades,


The highly skillful European Center model is going for 66F in Brookings, Oregon on Saturday....and 62F on Tuesday.  Brookings is well known for being the warmest location in the southern Oregon "banana belt."  And there is a reason (more later).


Our "code red" temperatures are associated with a high-amplitude upper-level (500 hPa) ridge over the northeast Pacific, with two "bookend" troughs on both sides (see below).  This is a very stable pattern.


Why does high pressure aloft make us warm--and particularly over the coastal zone? 

 First, high-pressure areas are associated with sinking air that prevents mid-level and upper-level clouds.  More sun! And the sinking air is also warmed by compression.   

But to really understand the implication of the upper high pressure, let's examine its reflection at the surface, illustrated by the forecast sea level pressure pattern at 4 PM Saturday (shown below).  The surface high is centered just offshore of central Vancouver Island, with northeasterly flow (winds from the northeast) to its southwest over coastal Oregon.


Northeasterly winds can sink over the western slopes of the Cascades and coastal terrain, producing MORE compression and warming.  Brookings is in the "banana belt" for a reason...it is downstream an area of continuous high terrain, extending all the way from the coast to the Cascade crest (see below).   So when the air sinks down such terrain it is very warm.

Northeasterly winds also keep the cool marine influence offshore and prevent the development of low-level fog and low clouds. 


So if you can, head to the Oregon coast this weekend for sun and springtime warmth.  Will be a bit cooler (mid-50s), but still decent in Long Beach, along the southern WA coast.   

But the southern Oregon banana belt is where you want to be.  Mid-60s and sun in mid-January is a real treat around here.



January 17, 2022

Mega Ridge of High Pressure will Lead to Perfect Coastal Weather

After months of jet streams, atmospheric rivers, snowstorms, cold waves, and low centers, a huge persistent ridge of high pressure will soon form along the West Coast.

But you will have to be patient.  For three more days, a series of weak systems will bring precipitation to the area. But then the region will turn dry, and in one area, the Pacific Coast, the temperatures will rise to very pleasant levels.  Book your room now!

First, the ridge. On Friday, high pressure will explode over the eastern Pacific and by 1 AM Saturday, the mother of all ridges will be evident aloft (500 hPa pressure level, about 18,000 ft) shown below.   Two troughs of lower pressure/heights are found on the sides.   This produces an OMEGA pattern, which is very stable.

UW Model Forecast for 1 AM Saturday


This pattern will hold in for the weekend and beyond.  At the surface, high pressure will be centered just offshore of Vancouver Island and inland, producing moderate easterly flow over the coastal zone of Oregon and southwest Washington.  Temperatures will warm as air sinks as it moves around the high and down the western slopes of coastal terrain (see sea level pressure map, with low-level temperatures, at 1 PM Saturday).


When I saw this chart I smiled and thought about immediately booking a room somewhere in the "banana belt" of the southern Oregon coast.  Let me show you why!

Here is the forecast of surface air temperature for 1 PM Sunday. Lots of reds--temperatures ABOVE 60F--along the coast west of the coastal terrain.   Warming offshore flow.  And the warmth will extend along the entire Oregon Coast and even southwest Washington (e.g., Long Beach).  Folks, it will feel like summer---a guarantee it!


In contrast, below freezing air will be ensconsed in eastern Washington, probably with some fog to boot.

The southern Oregon coast....a.k.a. the Banana Belt...is famous for enjoying warm days in winter.  All it takes is easterly (offshore) flow descending the regional terrain.



January 15, 2022

The Tonga Volcano Affects the Weather and Water of the Pacific Northwest

Yesterday, around 0400 UTC 15 January (8 PM PST 14 January), there was a massive, explosive eruption near Tonga, in the southern tropical Pacific, about 5642 miles from Seattle (see map).

The volcano was clearly evident in satellite imagery from the massive ash cloud (see below, about 1-h after the eruption)


The explosive eruption created shock waves in the atmosphere (pressure waves) that rapidly propagated away.  These waves are evident in some infrared (water vapor channel) imagery as concentric rings (shown below).


The oceanic eruption also pushed away a massive amount of water, which created a tsunami on nearby islands (such as Tonga) and deep water waves that moved away at the speed of a jet plane, reaching the West Coast this morning.  This is why some local tsunami warnings went out this AM.

The Pressure Wave Reaches the Northwest

Local barometers indicated a well-defined pressure wave passing over our region around 4:30 AM this morning.  Here in Seattle, the University of Washington barometer showed the feature, with an amplitude of roughly 2 hPa (2 mb).  The arrow indicates the feature. Very impressive.


So it took about eight hours and 30 minutes to go about 5643 miles--thus a speed around 664 miles per hour.  

The water wave moves slower, around 400 mph (and occasionally approaching 500 mph)....so a later arrival was expected.   Thus, at Neah Bay, at the entrance to the Strait of Juan de Fuca,  the water wave arrived around 9 AM (17:00 UTC as shown on the chart), as indicated by the waviness in the water level after that time.  The amplitude of the variation is around 2 feet.




If you really want to be impressed, check out the same figure at Monterey, California.  Just wow.  The amplitude was up to 3-4 feet.
An amazing event and one that shows how interconnected our planet is--both in the air and in the water.


January 14, 2022

The Best Weekend in a Long Time, Major Ridging Ahead, and the Mid-January Break: All in My New Podcast

After one dismal weekend after another, relatively dry conditions are ahead--thanks to persistent ridging--high pressure--over the northeast Pacific. 

The visible satellite image around noon shows sun reaching the surface for much of western WA, with the exception of fogged in areas near the water.   Lots of fog and middle clouds still over eastern WA.


A ridge of high pressure will develop aloft over the weekend (see map at 500 hPa...about 18,000 ft/..on Sunday morning below), leading to dry conditions and normal temperatures over much of the region.  But the ridge will not be strong enough to keep middle-level clouds away or precipitation from British Columbia.


Monday should be relatively dry until a moderate front approaches late in the day.

Check the podcast for more details on the forecast....and an explanation of the typical mid-January drying of the region--illustrated by the probability of measurable precipitation at Sea Tac below.



You can listen to the podcast below or through your favorite podcast server.


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January 13, 2022

Are Portions of Washington State in Severe Drought?

Today, NOAA released the latest drought update for the U.S., through their Drought Monitor website.

The updated map for Washington State, shown below, indicates normal conditions for western Washington and the western side of the Cascades.  

But east of the Cascades, it indicates large areas of moderate drought, severe drought, and even EXTREME drought.


I am very troubled by this drought depiction.  As demonstrated below, it simply doesn't appear reasonable.

Such excessive drought depictions are frequently provided by this source.  A major issue is that media and politicians pay a lot of attention to the Drought Monitor graphic, and it serves as one source of the ever-present drought narrative that is constantly being thrown around on social and traditional media (see below from CNN).


Courtesy of CNN, January 13th.

So is "extreme" or "severe" drought reasonable for eastern Washington State?  

Let me provide you with the data and YOU make your own appraisal.   As an aside, the NOAA drought monitor is a subjective graphic based on an analyist looking at a number of data sources.  It is not objective.

The Data

First, consider the precipitation departure from normal during the past three months (below).  Cumulative precipitation is WAY above normal in the west, and slightly above normal ove the majority of eastern Washington.


Snowpack?  The critical source of water during the summer?   Snowpack is well above normal for the entire state.


River levels?  Well above normal in the western part of the state, near normal in the east.


The extreme drought (red) area of the Drought Monitor depiction includes the drainages of the Yakima River, which provides critical water resources for agriculture for that area.  

How full are the important Yakima reservoirs? (see below).  Mama Mia!   The Yakima Reservoir system is HUGELY ahead of normal (blue line--this year, red line--average year).  On January 13th the reservoirs are as  full as they would normally be on April 1.  Plus, we have a huge snowpack that will top off the reservoirs even without any more rain.   The Yakima area is in good shape. I mean VERY good shape.
.

The water from the Columbia River is also important for agriculture, fish, and water usage in eastern Washington. 

What is the predicted flows of the Columbia in mid-May, right before the summer season?  Good news (see official prediction below)!    Predicted flows coming into the Grand Coulee dam are well above normal.



How about soil moisture in the upper layer (10 cm) around the state?  As shown below, most of the state has above normal soil moisture, including much of the "drought" area.  And a portion of eastern Washington is near normal (while).   
 

How about deep soil moisture (one-meter deep)?   Virtually ALL of the extreme drought area has WAY above normal deep soild moisture (green and blue).  The only place that is dry is along the eastern slopes of the north Cascades where there is record-breaking snow above it.  That soil will not be dry for long.


Finally, what about the famous Palmer Drought Severity Index, that includes both temperature and precipitation influences over an extended period of time (see below).  Eastern Washington is near normal.


The Bottom Line

I don't see how one can argue that portions of eastern Washington are in extreme drought.   Or severe drought.  Or ANY drought.

 Virtually every data source shows just the opposite (and there is more I could have provided to you).

Unfortunately, this exaggeration of drought by Drought Monitor is found in other areas as well. The nation is not well served by exaggerating drought.   As a result, poor decisions are made.

And all the resulting drought talk scares the population, and is used by some to exaggerate the impacts of global warming.

NOAA needs to carefully review the approach used for its Drought Monitor graphics and make changes that will lead to a more reliable, useful product.

Air Quality Declines As Inversion Slowly Weakens Overhead

 Inversions, in which temperatures INCREASE with elevation,  suppress vertical mixing, which in turn allows pollutant concentrations to incr...