Grass and Range Fires East of the Cascades

As expected, the massive lightning event this week led to the ignition of several wildfires.

But our region lucked out:  few fires were started on the eastern slopes of the Cascades within forested areas.  

This is because we are in the early season, which means less time for drying in the slow-to-dry forested areas, and because of the distribution of lightning (relatively little lightning on the eastern slopes).

Below is a map of the largest fires.  

Most were in grass and range vegetation, with the greatest fire activity in southeast Washington and northeast Oregon, where the most lightning occurred.

You can see the smoke in the midday high-resolution visible satellite image (as well as low marine clouds over western Washington).

Some satellites can observe the heat from the fires....and here is the same image with fire locations (orange dots).

The grass/rangeland of northeast Oregon is clearly the "hot spot" for the fires.

It is important to note that such fires have little to do with global warming or heat waves. 

 Light fuels, such as grass and range vegetation, are typically dried by now, and lightning events like this week have no correlation with a warming planet.

Want proof that the moisture level of the fuels (grass/range vegetation) was not unusual?

 Below is the data from the US Forest Service showing you the 100-hour fuel moisture levels. (100-hour fuels include dead organic materials, such as branches and dead roundwood, that measure between 1 and 3 inches in diameter.) The observed moisture levels (red line) are in the middle of the average range (gray shading).

But something has changed over the past decades the was made our grass/rangelends far more flammable...the invasion of explosive-burning cheatgrass and other fire-friendly species.

This map shows you the extent of the problem and why eastern Washington and Oregon are so vulnerable

Flammable grasses have taken over the region (see below), and ignition by lightning or human activities can start a firestorm.

And there is one more thing.  

To get large fire growth requires strong winds, and the weather systems that produced the thunderstorms also provided large wind gusts, both during the storms and after.   

Want proof?  Check out the maximum winds on Thursday (below).

Winds are declining now, and you can expect that the grass/range fires will quickly decline.

Massive Lightning Outbreak Hits The Northwest

One of the greatest Northwest lightning outbreaks in recent memory occurred today, with well over 5000 lightning strokes over the region.

Below are the strokes over the past 24 h:  very impressive.  

There were three major thunderstorm paths...one down the lowlands of western Washington, one along the coast, and a broad band in eastern Oregon and Washington.

Importantly, there were very few lightning strikes on the eastern side of the Cascades, which greatly reduced the chances of forecast fires there.

The massive lightning activity over northeast Oregon did start fires.

Normally, the Pacific Northwest is the poor stepchild of lightning activity in the U.S.  But look at the national lightning activity for the past 48 hr below.  For once, we were in the league of Florida or Texas!

The radar image this morning was enough to promote goosebumps for the meteorologically inclined:

And today's precipitation totals were quite significant, with several locations receiving over a half-inch (see today's totals below).

The visible satellite image  around 10 AM looked like something out of Oklahoma:

During the morning, several folks told me they saw funnel clouds, based on pictures like this:

I saw such clouds myself... which result from aircraft passing through a low cloud deck. NOT a tornado.

Let me end with a truly remarkable image.

Low clouds were left in the wake of the thunderstorms over western Washington, but Mount Rainier extended above the clouds. Eastern Washington is now experiencing plumes of smoke from fires ignited by the lightning over northeast Oregon. The green areas show lightning strikes.

  

 

Thunderstorms and Rain Coming to the Northwest

For most summers, during July or August there is an intrusion of "monsoon" moisture from the southwest into our region, resulting in showers and thunderstorms...and this year will be no different.

Such thunderstorms can be both good and bad.  Good at providing needed rain and lessening fire risk, but bad if lightning starts fires.

The predicted totals through Friday morning (seen below) range from a few tenths to a half inch, with higher values along the coast.

The wet fun will begin later this afternoon and evening as convection and thunderstorms build near the crest of the Cascades (see forecast for 5 PM below).

Overnight, more serious thunderstorms/convective showers will move into the region, as suggested by the forecast weather radar image at 2 AM from the University of Washington forecast system:

The latest forecast of the NOAA HRRR model is quite similar (simulated radar at 1 AM shown below).

Why this wet bounty?

Two things are occurring together.   The upper-level pattern includes an approaching upper-level trough (500 hPa, about 18,000 ft shown for tomorrow morning).  Such troughs produce upward motion (which helps initiate cumulus clouds) and bring in moisture from the south.

Such "monsoon" moisture and unstable air from the southwest are evident in the forecast below.

Total water vapor content of the atmosphere this evening.  

Blue and red are higher values

Enjoy the show overnight!

Wildfire Smoke Fills the Skies Above The Northwest

 If you viewed the skies around sunrise and sunset during the last day, it was evident that a massive cloud of smoke had moved in overhead.

For example, here is a northwest view from the Seattle PanoCam just before sunrise this morning.   Stunning.  Lots of smoke in the sky.

And if you needed more evidence that our sky was full of smoke, below is the visible satellite image at 6:52 AM this morning (Monday, July 13).  

Wow.  Lots of smoke over our region.

Yet, with all this smoke, surface air quality is excellent, as shown by the latest observations from the Puget Sound Clean Air Agency (green means good air quality).

How could this be?

The answer to this conundrum is that the smoke is located many thousands of feet aloft, so high that it can not mix down to the surface.   

To prove this, here are observations from a laser-based ceilometer in Marysville, Washington.  This device shoots a laser vertically, allowing it to sense smoke and clouds above the surface.

This morning, the smoke was around 3000 meters (about 10,000 ft) above the surface.

Where did this smoke come from?   

Not from local fires, but from major fires in the Canadian arctic and sub-arctic regions, something shown by the visible satellite image two days ago (see visible satellite image from two days ago):

This smoke then swung around an upper-level low off our coast and into our region.   I can demonstrate this with the upper-level weather map (about 18,000 ft, 500 hPa pressure) for early Sunday morning (below).  The wind barbs show the wind speed and direction.  

Air from northwest Canada moved offshore over British Columbia and then swung around the low and into the Pacific Northwest!

The pattern is now shifting, and the smoke aloft will move out of our region today.

The Best Weather In the U.S.

 If you asked Google AI where the best weather in the U.S. will be, the answer will warm your heart:

Seattle gets called out with "perfect weather conditions".    As a trained meteorologist, I concur.

The forecast high-temperature map for Sunday across the U.S. shows only one urban area in the upper 60s to low 70s: western Washington.  Even eastern Washington is reasonable.

You dislike humid conditions with high dewpoints (above 60F) and want to avoid very dry, parching air (dewpoints below 40F)?     

Western Washington and Oregon are for you! (see plot of forecast dewpoint temperatures for 5 PM Sunday below)

Want sunny skies on Sunday?   Western Washington and Oregon residents will see blue skies.

And you like some light winds, but not too strong?  The wind gust forecast for tomorrow shows perfect conditions over western Washington.

Air quality?    Clean air (green dots) over the Northwest (see below).   You can take a deep breath!

There is so much negative information today about the environment, so it is good to acknowledge when things are spectacularly nice.    

I won't get many online hits in saying this... but it is true.😋

The North American Monsoon is About to Start: Part of the Northwest Will Get A Piece of It!

 Late June or early July is the traditional start time for the North American (or Southwest) Monsoon, during which moisture streams northward from Mexico into the southwestern U.S., bringing substantial showers to Arizona, New Mexico, Nevada, and sometimes Oregon, Idaho, and eastern Washington.

See the schematic below.  Such monsoons are often associated with an area of high pressure over Colorado and northern New Mexico, which draws moist air from the Gulf of Mexico into the American Southwest.

In a few days, the monsoon will get revved up, and some of the wet action will reach portions of the Northwest.

Let me show you!

Here is the predicted precipitation total over the next 10 days.  Some of the Mexican moisture pushes into Arizona and Nevada, and a small amount will extend into eastern Oregon.

The official NOAA Climate Prediction Center 6-10 day forecast is for wetter-than-normal conditions over the southwest U.S. The far southeastern portion of Oregon gets a wet taste of it.

As expected, this monsoon moisture will be driven by an upper-level high over the 4-corners area that will move moisture into the southwest from the southeast (500 hPa --about 18,000 ft map for each Sunday morning is shown below)

Here is the predicted precipitation for Tucson, Arizona.  Very wet!

There will be some good thunderstorms in Arizona if you enjoy big boomers.

This is not a particularly hot pattern for the Northwest, and Seattle will stay moderate in temperature (see below).

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Announcement

I will hold a special online Zoom session at 10 AM on Saturday for Patreon supporters. Will talk about the latest forecasts for the remainder of the summer and answer your questions!

Cooler Than Normal Water Off the Northwest Coast

One of the reasons Northwest weather is so temperate in summer is the cool coastal waters off our coast.

And this year, we start the summer with surface waters cooler than normal.

This is illustrated by the sea surface temperature anomalies (differences) from normal (below), with blue indicating cooler than normal water.

Below is a map of sea surface temperatures off the U.S. West Coast (°C).   The purple and blue colors indicate the coldest temperatures.   You will need a sweater to enjoy a coastal stroll!

Why such cold water along the coast? 

One reason is the upwelling of cold water from below, as illustrated by the figure below. Such upwelling is forced by northerly (from the north) winds along the West Coast.

Importantly, these northerly winds have been stronger than normal for the past month.

Why? 

Because of stronger-than-normal surface high pressure offshore of the northwest.  This is demonstrated by the figure below, which shows the sea-level pressure anomaly (difference) from normal over the past month.

The red area indicates a much higher-than-normal high-pressure area offshore.

Since winds move clockwise around high-pressure areas in the Northern Hemisphere, this implies enhanced northerly flow along the coast, something shown explicitly in the figure below (which shows the wind differences from normal of the past month).

With this persistent pressure/wind pattern in place, the current 5-day forecasts are for colder than normal conditions over western Washington, Oregon, and British Columbia (blue and green indicate colder than normal conditions)

Keep your sweaters handy!

Wind and Fireworks Brings A Fast-Growing Wildfire Near Lake Chelan

 The  Chelan Hills fire, reported to have been started by some irresponsible fireworks Saturday morning, has now spread to over 10,000 acres (see map below).

A high-resolution visible satellite image this morning shows the burnt area (dark color), and the satellite imagery shows some still-active fires (red dots).  Smoke from  another (smaller) fire is apparent to the southwest.

The fire started in grass and range vegetation, not forest.  

Importantly, this vegetation was NOT unusually dry, as shown in the figure below, which provides 100-h fuel moisture levels on the eastern slopes of the Cascades.  Red is observed moisture level, and the shading shows the normal range.  

Current moisture levels were above normal.

So "climate change" can not be blamed.

What can be blamed was strong winds.  

Winds that were skillfully forecast by the UW WRF modeling system and the NOAA models.  To illustrate, below is the wind forecast for Saturday afteroon be the UW WRF weather model....strong winds were predicted around Chelan!

Below are the strongest observed winds yesterday around the fire area.  A 36 mph gust was observed near the fire start.

Winds at this location really revved up during the afternoon and early evening (see below).

At the same time, relative humidity plummeted to less than 20%--the result of drying of air moving downslope on the eastern side of the Cascades.

There is reason that wildfire starts are maximized on July 4th.  

The ignitions are there, the grasses/range vegetation are dry enough to burn, and it is early enough in the summer so that strong onshore flow produces powerful winds.