June 19, 2024

Mountain-Top Instability

Over the lowlands of Washington State,  today was sunny and generally clear.  Not a drop fell out of the sky.

But something very different happened in the mountains, where the atmosphere became unstable, resulting in cumulus clouds and showers.  Even some lightning!

Let me show you and explain.

To begin, here are two visible satellite images:  one at 6:30 AM and the other at 5:30 PM today.

The morning image had little clouds with snow visible at higher elevations

But the story is different at 5:30 PM.

The lowlands are still clear, but many clouds are over the mountains.  Cumulus clouds, including some tall cumulonimbus.

You can see the changes from ground level from the wonderful Crystal Mountain cam.

At 6:20 AM it was clear looking to the east.

But by 10:40 AM, shallow cumulus clouds were forming over the peaks.

By 1:20 PM, the clouds had become more widespread and deeper.

The 6:10 PM shot shows deep cumulus that were precipitating.  You can see the rain under the cloud base (called virga).

In fact, there was measurable precipitation at several mountain and downstream sites during the past 12-h (see plot below).

So why cumulus clouds and precipitation in the mountains (also known as convection) and not over the lowlands?

Cumulus clouds are associated with atmospheric instability, in which the atmosphere convects with up and down motions, not unlike what occurs in your hot cereal saucepan or in a lava lamp (see below).

Convection breaks out when the temperature decrease with height gets sufficiently large.  Normally this is due to heating near the surface but it also can occur when there is cooling aloft.

Mountains act like high-elevation heat sources, particularly after the high-elevation snowpack has melted.  That results in a larger temperature change with height above the mountains than over the lowlands.  The air over the mountains becomes unstable, leading to cumulus clouds (see schematic below).

This effect is largest in the afternoon when solar heating is the greatest.

But wait!  There's more!   During the day, there is upward motion on the heated slopes of terrain, resulting in strongly enhanced upward motion over the mountain tops.  Upward motion contributes to cloud formation and the development of instability over the mountain crest.

Both of these effects were occurring today, resulting in lots of cumulus clouds and some rain over the higher elevations of the Cascades and other regional mountains.

June 17, 2024

Is Mid-June Getting Warmer or Colder?

 As I will demonstrate below, this past week has been unusually cool around the region.

But that leads to another question....is mid-June getting warmer or colder?   

A strange question when there is so much talk about global warming.  But as you will learn below, the truth will be stranger still 😀

Let's start is an image this morning at the Paradise Visitor Center on Mount Rainier (about 5000 ft up). They had a mixture of rain and snow showers with fog.  Yuck.   Not my choice for hiking!

Next, consider the differences in daily average local temperatures from normal for the past week (below). Green, blue, and purple colors are below normal.

No wonder I have been wearing my sweatshirts!  Most of Washington State has been cooler than normal and much of western Washington has been 3-5F below normal.    My tomato plants have been struggling for a reason.

But you didn't need me to tell you it has been cool and drippy.  

But now something interesting:  is mid-June getting cooler or warmer in our region?   

Below I have plotted the trends of temperatures for the past week (June 9-16th) at Hoquiam, on the central WA coast.   This was the FIFTH COOLEST mid-June since 1953 (roughly 70 years!)  And there is little long-term trend (brown line)

At Olympia, there was not only a colder than-normal mid-June, but mid-June is getting COOLER over time.

At Bellingham, mid-June temps this year were in the top-ten cold years, and there is no trend up or down in mid-June temperatures.

I am not showing SeaTac Airport because the site is useless for any climatological work with the addition of a third runway, greatly increased aircraft operations, and a large amount of development around the airport.

What about Wenatchee in eastern Washington, located in prime tree-fruit country? (see below)

OMG!   Not only was this a cold mid-June, but the long-term trend is for cooling.

Can this REALLY be true?   Consider Yakima, also in prime agricultural land.  There is NO trend in temperatures in mid-June.

A similar lack of mid-June temperature trend is also true in Spokane.

So how can this be?  With all the global warming talk, how could our mid-June temperatures be unchanging or cooling?

The key reason is our location near the cool Pacific Ocean.  During mid-June, we still have a vigorous onshore flow of cool ocean air that isolates much of our region from the warming of the interior.

In fact, enhanced warming of the interior can cause pressure to fall more there, which creates MORE of an onshore pressure difference (high offshore and low pressure over the interior).

We have global warming protection this time of year!

Such climate subtleties are important but unfortunately missing in most media coverage.


A Steve Pool memorial undergraduate scholarship has been established in his honor (see below)

Once funded by contributions, this new undergraduate scholarship will provide financial assistance to promising Atmospheric Sciences students, fostering the training of the next generation of meteorologists and atmospheric scientists.

If you want to contribute or learn more about Steve, check out the webpage below.   Thanks so much....cliff

June 15, 2024

New Podcast: Showers, Warm Up and Winds on the Eastern Cascades Slopes

 Cold, moist unstable air has been moving into the region on Saturday, with the showers obvious on the high-resolution visible satellite imagery (see below).

If hiking on Mount Rainier you would have "enjoyed" a mixture of rain and snow with very little visibility (see below).

Here in Puget Sound country, a strong Puget Sound Convergence Zone is laying down a band of heavy rainfall across the Sound (see radar)

The cool air around western Washington is pushing strong winds down the eastern slopes of the Cascades (see max winds today below).  Good for wind energy, bad for fires.

All is explained in my podcast!

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

Some major podcast servers:

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June 13, 2024

Undergraduate Scholarship Fund in Honor of Steve Pool

Steve Pool was a leading television meteorologist in Seattle for nearly 40 years..... but he was so much more.

In addition to providing meteorological insights and weather education to millions of viewers across western Washington, Steve was among the first African-American TV weathercasters in the nation and frequently contributed to weather coverage on national programs such as Good Morning America.  

He was committed to the University of Washington and the UW Atmospheric Sciences department, establishing an internship program that trained dozens of UW students in broadcast meteorology, including current KOMO lead meteorologist, Shannon O’Donnell. 

Steve served as Master-of-Ceremony for many departmental and UW public outreach functions, greatly contributing to their attendance and success.  

He also fostered several public education activities, such as his annual weather program before a Seattle Mariners baseball game, with the effort staffed by UW Atmospheric Sciences undergraduates.

Steve passed away last fall, but his numerous contributions, extraordinary character, humor, and priorities don't have to be forgotten.

You can help.

memorial undergraduate scholarship has been established in his honor (see below)

Once funded by contributions, this new undergraduate scholarship will provide financial assistance to promising Atmospheric Sciences students, fostering the training of the next generation of meteorologists and atmospheric scientists.

If you want to contribute or learn more about Steve, check out the webpage below.   Thanks so much....cliff

June 12, 2024

More Rain for the Northwest is Good News for Wildfires

After a very pleasant dry spell, another rainy period is ahead for the western side of the region and the Cascades on Friday and Saturday.   And there is no hint of heat waves in our future.

Today and Thursday will be partly sunny, with highs in the upper 60s to low 70s in the west, with the Columbia Basin being about 10F warmer.   Typical June weather.

But on Friday, an upper-level low-pressure area (or trough) will be moving in (see below for 8 PM Friday), bringing clouds, showers, and cooler temperatures.

Such features have been persistent this spring.

The forecast 24-h precipitation total ending 5 PM Friday shows showers in the west, with the heaviest precipitation along the coast.  Eastside dry.

The next 24-h (ending 5 PM Saturday) is quite wet in the West, particularly over the western slopes and crest of the Cascades.  

Perhaps not the best day for a Cascade hike.

As the system passes through, the region will dry out on Father's Day (Sunday), except for a band of Puget Sound from the Puget Sound convergence zone and over northeast Washington.

The predicted temperatures for Seattle (below), show a substantial cool-down over the weekend (about 10F below normal on Saturday), but warming to near-normal conditions (low 70s) next week.   Again, add about 10F for the Columbia Basin.

All the gnashing of teeth and predictions about summer drought and wildfire by certain media outlets does not appear to be well-founded.  

Below is the latest one-week predicted significant fire potential by the Northwest Interagency Coordination Center, which is responsible for region wildfire prediction.  Green indicates below-normal potential.   Looks favorable.

The most skillful extended forecast is by the European Center and their latest guidance predicts COOLER than normal conditions for the next month over most of the region (see below)

Of course, we have the challenge of July 4th, where crazy people shooting fireworks start many fires. often in dry grass.  Hopefully, the grass will be moist this year.

June 09, 2024

Lightning Returns to the Pacific Northwest

 Lots of thunderstorms, some approaching severe levels, have hit eastern Oregon and Washington during the past day.....and there are severe thunderstorm warnings out between Wenatchee and Spokane as I write this blog (see below).

The latest radar image over eastern Washington shows strong storm cells, with the red colors indicating substantial radar reflectivity.   Such high levels are either very heavy rain or hail. 

Earlier today (around 3:30 PM) similarly strong storms were moving eastward across southeast Oregon (see below)

Precipitation during the past day has been substantial over southeastern Oregon (up to 1.23 inches) and northeast Washington has also experienced some of the thunderstorm showers (see below).

This is the first major lighting event of the year for our region.    Yesterday (Saturday), there was a substantial number of lightning strikes over eastern Oregon ( see below).

The latest lightning strike map (at 7:50 PM Sunday) shows plenty of lightning, with thunderstorm cells over eastern Washington and others over southeast Oregon.

And here is the total lightning strike picture for Sunday.  Southeast Oregon and downstream are well covered by lightning, with quite a few over NE Washington.

So why so much lightning?

Today an upper-level trough moved through, as shown by the weather map at roughly 18,000 ft (500 hPa) this morning at 8 AM (the red dashed line shows the trough line).   In front (east) of the trough, there is both upward motion and the movement of warm, moist air from the south, both very favorable for generating thunderstorms.   

The atmosphere over eastern Washington and Oregon had lots of CAPE (Convective Available Potential Energy)... think of this as fuel for thunderstorms.  

To illustrate,  here is the CAPE prediction for 8 PM tonight (Sunday).  Some values getting as high at 600 (J/kg).  Decent for around here, a big yawn for those in the Midwest.

All our local thunderstorm action will be over over night as the trough moves inland and cooler marine air moves into the region.

June 07, 2024

New Podcast: Perfect Saturday Followed by June Gloom

It is a phrase that puts fear into the hearts of all true Northwesterners:  June Gloom.

You thought we escaped it?   Think again.

But first, we have an even warmer day than today in store for Saturday, with Puget Sound Country hitting 80F and another ten degrees over the Columbia Basin.

During June Gloom periods the northeastern Pacific fills with low clouds, which push into western Washington and Oregon (see below).  In fact, the whole West Coast can suffer from this affliction.

The cloud coverage this morning shows why today was so warm:

But Sunday morning is a different (and cloudier) story.

As is Tuesday (below)...and Wednesday and Thursday.... is the same.  That is June Gloom!

Anyway, check out my podcast for more details:

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

Some major podcast servers:

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Mountain-Top Instability

Over the lowlands of Washington State,  today was sunny and generally clear.  Not a drop fell out of the sky. But something very different h...