Pyrocumulus Over the Olympic Peninsua

 The wildfire creates a large cumulus or cumulonimbus cloud, we call it a pyrocumulus.

Yesterday, a large pyrocumulus cloud formed over the southwest side of the Olympics, associated with the 2000-acre Bear Gulch fire (see map below).

The fire, which was human-ignited,  expanded rapidly yesterday afternoon and was very evident in weather satellite imagery (see below).  Very impressive.

The pyrocumulus was high and substantial enough to be seen on local weather radars (below).

And, of course, it was apparent visually (see examples below).

With cooler temperatures expected later this week, with some mountain showers, one can be hopeful that the expansion of this fire will be limited.

Why So Many Thunderstorms in Eastern Oregon?

 Day after day, satellite and radar imagery show big cumulus clouds and thunderstorms over eastern Oregon, while most of the remainder of the region has none.

To illustrate, below is the visible satellite image from Monday afternoon, with lightning shown by the green dots.

The radar earlier in the day also picked up the thunderstorms over southeast Oregon

Adding up all the forecast accumulated precipitation through Saturday AM, you can see the wet situation from the Cascade crest into eastern Oregon.

This pattern is not a fluke this year.  

Below is the average lightning density map for the U.S. (2015-2020).   Not much lightning along the West Coast due to the cool Pacific, with eastern Oregon getting the most in our region.

MUCH more in the southeast U.S.

You can see the lightning-prone eastern Oregon in the expanded map below.

So why are thunderstorms favored in eastern Washington, you ask?

There are at least three reasons.

Thunderstorms are associated with vertical instability driven by rapidly decreasing temperature with height.   Warm surface temperatures are thus good for business.

The Pacific Ocean is relatively cool, with surface temperatures around 50°F. This cool air spreads over western Oregon and Washington and works against the instability that produces cumulus convection.

The second reason is explained with a topographic map below.  Much of eastern Oregon is an elevated plateau, which serves as an elevated heat source during the day.  Elevation heating helps enhance the vertical temperature change (gradient) aloft, which helps produce convection and thunderstorms.

Finally, southeast Oregon is closer to the northward plume of moist, unstable air associated with the Southwest Monsoon, as illustrated by an example from a few years ago (below).

Interestingly, there has been a very, very weak Southwest Monsoon year so far.  As a result, precipitation is WAY lower than normal this summer in Phoenix (see below, green is this summer, purple line is normal).

Northwest Rain During the Driest Time of the Year

 We are now in the driest period of the year in the Pacific Northwest.   Below is the daily climatological probability of a trace or more of precipitation in Seattle.

Just amazing: we bottom out from roughly July 5 through August 15th, with the lost few days of July (NOW) the most arid.

Crossing the Cascades to Sunnyside, we find a similar dry period...although the general level is much lower in the arid Columbia Basin.

The reason for this climatological Northwest dry period is clear:  the jet stream and storm track are not only weakened in mid-summer, but are also positioned to our north during this period

Furthermore, with cool waters offshore, we don't get many thunderstorms, unlike much of the U.S. 

Interestingly, the models are now suggesting that many will experience precipitation during the normally dry period.....let me show you.

 Starting with the latest UW WRF model forecast for accumulated precipitation over the next five days, one notes substantial precipitation from northern California into eastern Oregon, with a few showers making it into the southern WA Cascades.  

Most of this precipitation is from thunderstorms, as shown by the simulated precipitation on Thursday around 6 PM.

This precipitation pattern has been persistent over the past few weeks, with portions of northern CA and eastern Oregon wetter than normal (see below, green and blue colors).

A number of model runs are showing a significant change in the pattern of the past few weeks with a series an energetic troughs of low pressure pushing south into British Columbia, shifting the rain shield south.

The latest UW extended precipitation total through Monday afternoon (August 4th) shows the moisture.  Impressive for this time of the year, with welcome precipitation over the wildfire region east of the Cascade crest.  

Puget Sound will be rainshadowed by the Olympics.

The ensemble systems of many forecasts concur with this moist forecast, and the NOAA Climate Prediction Center 6-10 day precipitation forecast is for above-normal precipitation over our region.

This moist period will be associated with cooler-than-normal temperatures and will help restrain the wildfire threat over the region.

How to Save Seattle (And Other Locations) from Weather-Related Tragedy

The flooding tragedy in Texas had a component common to nearly all recent weather-related disasters: 

The weather predictions and warnings were excellent, but local governments, utilities, and other responsible parties did not use the excellent meteorological guidance effectively.

Similar poor use of skillful forecasts has occurred frequently and recently, such as the strong winds that produced massive fires in Maui and Los Angeles. Or the excellent precipitation forecasts for Hurricane Helene that were not effectively used to warn.

We should not feel too smug here in the Northwest.

During the past five years, hundreds have died in our region from meteorological conditions.   From heat and cold.  From trees falling during intense windstorms.  Due to river and coastal flooding.  Others have fallen from accidents on "black ice", while many have been sickened by wildfire smoke.

In virtually all of these cases, the forecasts were good to excellent, and lives could have been saved and damage avoided if the correct actions had been taken.

We need a better way to make both individuals and governments better aware of the nature of the meteorological threats.

Seattle could help lead the way.

Imagine an online website/smartphone app that would warn of all the major weather-related problems (see example below)

An automatic system could monitor these threats.   In parallel, the system would also monitor the warnings/forecasts by the National Weather Service.

If there are threats for any of these issues in Seattle or at your location, you would be warned.  Click on the item, and detailed information on the threat would be provided.

Some of us at the University of Washington have already built some of the necessary components:  Seattle SnowWatch and Seattle WindWatch. The observational and model data are available.

The integration could be done in a few months, allowing the City and local residents to enjoy state-of-science warnings and weather information.

Looking beyond Seattle, the NOAA and other federal agencies could build, perhaps in concert with the private sector, a national app like this for smartphones and other devices.

A one-stop shop for all environmental threats.    

I should note that there are already some phone apps that cover part of this territory, such as Storm Shield (see below).

It is important to remind folks in areas without cell service that the National Weather Service still maintains NOAA Weather Radar, which will beep and provide terse emergency weather information during dangerous periods.

You can even get one with a strobe light and bed shaker (see below)

Announcement

I will hold a special online Zoom session at 10 AM next Saturday for Patreon supporters.  Will answer questions,  take a deeper dive on the late summer forecast, and consider the outlook for next winter.

Crystal Mountain Cam Captures Fire Started by Lightning Strike

Yesterday, a series of thunderstorms moved through the central Cascades.

For example, the satellite-based lightning detection system at 2:30 PM yesterday showed several lightning strikes in the Mt. Rainier area (red markers are lightning strikes and shading indicates clouds)

 

Here is a close-up view at the same time.  The tram to the top of Crystal Mountain was shut down due to lightning yesterday afternoon....and for good reason.

We had a front row seat of the impacts of one of these lightning strikes from the Crystal Mountain 360 Cam.   I will show you a series of cam images looking toward the west-southwest, with Mt. Rainier on the left side.

At 2:20 PM, there were plenty of ominous clouds and some were precipitating.  There was some lightning at this time (not apparent in this image).

A lightning strike occurred during the next few minutes and by 2:50 PM some smoke was apparent...a fire had been started.

At 3 PM flames were evident.

And the fire was putting out a lot of smoke at 3:10 PM

This morning there was no smoke or hint of the fire.

Perhaps this is due to the substantial amount of rain that fell with the series of convective storms, with a nearby location getting three-quarters of an inch (blue star shows the fire location).

The good news regarding this event is that it was wet enough that the many lightning strikes apparently did not start many new fires.

Lightning and Thunderstorms Over and East of the Cascade Crest

 The National Weather Service now has a flash flood warning due to potential thunderstorms over north-central Washington, from the North Cascades northeastward.

As I will describe below, thunderstorms are a good bet, but I suspect the flooding threat is relatively low.

Convective storms, some with thunder and lightning, did occur yesterday (Sunday) over the Cascades and were even visible from Seattle:

Terminology alert:  meteorologists often use the term convection for unstable situations that result in cumulus clouds and sometimes thunderstorms.  Convection is generally associated with a large decrease in temperature with height, causing the air to convect, with up and down motions.

The convection/thunderstorms yesterday produced precipitation over northeast Washington (see totals below), with only modest lightning.

Today there is potential for more unstable air, convective showers, and some lightning and thunder over and east of the Cascades.

The visible satellite at 9 AM this morning shows considerable cloudiness over the region, with some convective cells evident over south-central WA (whiter areas).

The current (10:42 AM) weather radar is picking up some showers with this convection/instability:

Today's model runs are emphatic that convective showers will develop this afternoon over the Cascades, the Okanogan, and northeast WA.

Here is the simulated radar impact at 3 PM from the UW WRF model, with the orange colors showing the heaviest rain from the convection.

The forecast of the NOAA HRRR model at the same time is similar.

The total precipitation through 5 AM Tuesday (shown below) is moderate, with highest amounts reaching 1.5 inches.  Not enough for flooding.

The occurrence of this precipitation is associated with an upper-level low over eastern WA (see map today at 2 PM for around 18,000 ft).

My only worry about this event is that the associated lightning could start some wildfires.    One reason we have had such few fires this summer is the lack of lightning-induced fires.

This is not an accident:  the same large-scale conditions that gave us a dry summer have also reduced lightning.

___________________-

My Atmospheric 101 course this autumn.

This general intro to atmospheric sciences can not be taken remotely and asynchronously, meaning you can take it at home and watch when convenient.  More information here.

No Heatwaves During the Warmest Time of the Year

 As shown by the temperature plot below for SeaTac Airport, the next few weeks are climatologically the warmest of the year (brown indicates average temperature range, red shows record highs).   SeaTac's average high temperatures during the next weeks are close to 80°F, and many of our record highs have occurred during late July and early August.

There are all kinds of definitions for heat waves, but whatever your definition, model forecasts are pretty emphatic that there WILL NOT be any heat waves during the next week or so in our area.

Consider the forecast by the National Weather Service's National Blend of Models--their most highly skillful temperature forecast system (below).  High temperatures undulate around 80F, with the highest at 85F next Wednesday and the coldest (74F) today.

Every day, the low temperature drops in the 50s.    Very, very average weather.  Perfect weather by my book.

The National Weather Service's Climate Prediction Center's 6-10 day forecast (below) predicts BELOW NORMAL temperatures for western Washington and much of California.   Near normal in eastern Washington. Warmer east of the Rockies.

Do I have confidence it this forecast?  

Yes, because the ensembles of many forecasts....a tool to determine uncertainty in the predictions... shows that virtually all the forecasts are in line with the above forecast.  

To show this,  the GEFS ensemble of many National Weather Service Model forecasts is shown for the next week below.   Most forecasts provide a similar story, and NONE are going for a big heatwave.

You can go to the bank with this forecast 😀.

So what is going on?

Consider the large-scale upper-level weather pattern shown by the heights of the 500-hPa pressure surface (think of this as pressure around 18,000 ft).

Monday morning, there will be a sharp trough of low pressure over our region.....a cold pattern.

Wednesday afternoon, the trough moves out, and an extension of a Pacific ridge/high pressure extends over our region.  This is when our temperatures climb into the mid-80s.

Next Friday, a cold trough moves over the entire West Coast (sweater alert!).

And on Saturday, a sharp, strong trough has moved over Washington and southwest BC.

The bottom line:  no heatwaves and comfortable sleeping at night with AC west of the Cascade crest.

Announcement

I will hold a special online Zoom session at 10 AM next Saturday for Patreon supporters.  Will answer questions,  take a deeper dive on the late summer forecast, and consider the outlook for next winter.