September 18, 2021

Big Winds, Heavy Rain, and Now Thunderstorms

 Nearly 100,000 Washington State power customers lost power last night as strong winds first hit Northwest Washington and then spread across the remainder of the western interior as a powerful front crossed the region during the late evening.  Trees are very vulnerable to the first windstorm of the season, particularly if they are fully leafed out.



Winds gusted to around 60 mph over Northwest Washington, 40 mph over the lowlands of the South Sound, and reached 103 mph at Camp Muir on Mount Rainier.

The power outage map from Puget Sound Energy last might shows the damage, centered around NW Washington and the south Sound towards the Cascades.


Here are the top wind speeds on Friday (click to expand).  A gust to 63 mph a Whidbey Island Naval Air station, nearly the same at Port Townsend, and nearly 50 mph on the San Juans.   These winds occurred during the afternoon before the front made landfall.   



Strong winds over NW Washington are very typical for winter weather systems around here,  with the powerful winds responding to the strong pressure difference (gradient) produced downstream of the Olympics.  This is illustrated by the forecast pressure (brown lines are isobars, lines of constant pressure) and winds (color shading) at 5 PM yesterday (below).   Look carefully and you will see a large change of pressure over northern Whidbey Island....this accelerated winds from the southeast.


Over the south Sound, the winds gusted to 40-50 mph last night over the lower elevations, 70-80 mph on lower peaks, and over 100 mph on Rainier.


These winds occurred during the later evening as the strong front went through....the feature I warned about in my last blog.  The radar image at 11:11 PM last night showed a line of strong radar return with the front (the arrow shows you the feature).


The frontal winds came up very quickly and dropped very quickly, as illustrated by the winds at the USDA RAWS site in Enumclaw, southwest of Seattle.  A gust to 36 mph with the front.


And this was a particularly strong front with a VERY large temperature change associated with it.  To prove this, here are the temperatures at Enumclaw.  Temperatures rose before the front to 72F and then crashed to the lower 50s within a few hours.  Don't see that kind of large temperature changes with fronts very often around here!


Precipitation?   This system brought plenty, ranging from 4-6 inches in the mountains to around a half-inch in the rain shadowed areas.


Rivers are way up right now, with many Washington rivers above normal levels.  But no flooding because they started at below-normal to normal levels.   

Part II. Thunderstorms and showers

The excitement is not over yet!  With an upper-level trough/low approaching and cooler air moving in aloft, the atmosphere will be primed for convection and thunderstorms.  So get your lightning rods ready.

The latest visible satellite image shows the front moving through right now (the solid band of clouds) but also displays lots of convection (instability showers of cumulonimbus) offshore (these are the popcorn-appearing features).  Those showers are strong and have our names on them.  But most of you will have a break this morning and early afternoon--so have fun outside this morning if you can.


A particularly potent band will come through this afternoon and evening (see the simulated radar image at midnight tonight below).   Many of you will hear the rumblings of thunder.  And more shower action on Sunday.  

It is good to have active weather back...and I note that it is quite typical for this time of the year.

Forecast radar reflectivity at midnight tonight.


September 17, 2021

A Potential Intense Feature Moving Through Tonight. My New Podcast. And Why are Northwest Summers so Dry.

A potentially VERY intense frontal feature will move through western Washington tonight, one that could produce intense rainfall and localized urban flooding.

A very strong front will move through this evening, crossing Puget Sound sometime between 8 PM and 11 PM.  This front will bring INTENSE, heavy rain for a short period (less than an hour) that will cause localized flooding and strong winds.  There could be a thunderstorm with it.   

To illustrate this threat, here is a simulated radar image for 10 PM tonight.  Wow. The orange/red colors indicate very heavy rainfall.  The NOAA HRRR model is doing the same thing.  


This feature will pass through the coast a few hours earlier. 


I would not be driving during this event and if you live in a basement apartment with flooding issues, I would be watchful.  The City of Seattle used to have the RainWatch system that provided warning capabilities for such events, but since they dropped it a few years ago,  I am providing the heads-up manually. 

The total precipitation for the storm follows the previous guidance (the total through 5 AM Sunday is shown below).  Even eastern WA gets good rain, with over 5 inches in portions of the Olympics and Cas Cascades.

In western Washington, the rain will be very heavy tonight, with showers into Sunday.  Good chance of thunderstorms on Saturday and Sunday.

I talk about the forecast in-depth in my podcast.   

In the second section of the podcast, I explain why the Northwest has some of the driest summers in the nation.  In fact, the entire West Coast is very dry (the plot below shows you the average July precipitation).  By the end of the podcast, you will know the reason.
 




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September 16, 2021

The Winds and the Rain. Plus, My Atmospheric Sciences 101 Class this Fall

 I have talked about the rains in my previous blogs and everything is pretty much on track.

I do not want to overhype the event:  it will be roughly the same as one of our typical vigorous winter weather systems.  

This is not a major atmospheric river event that produces flooding.   And that is particularly true because our rivers are starting at relatively low flows.  Not a major windstorm. But it will be a shock to many because we haven't experienced a real storm in a long time.

But all said and done, the water vapor satellite imagery is quite impressive this morning (see below).  A huge plume of water vapor is heading our way and is now right off the coast.

The rain sequence from the last European Center Forecast is shown below.

The accumulated precipitation through Friday a 2 PM shows the rain shield spreading over northwestern Washington


By 11 AM Saturday, the rain has really piled up, particularly over the Olympics, North Cascades the southern BC.  Roughly an inch over the lowlands and several inches in the mountains.


And by11 AM Sunday, substantial precipitation has spread into Oregon.  You note the rainshadowing to the east of the coastal mountains and Olympics.


And there will be some substantial localized winds, particularly on Friday.   As the system approaches Friday morning (11 AM shown below) strong pressure differences will drive strong winds (gusts of 40-50 mph) along the coast and over the waters of Northwest Washington, and locally winds could be even stronger.
Later during the afternoon (below), the winds will weaken in those areas and strengthen over Puget Sound, with some gusts over the water to 40-50 mph.  Some exciting ferry rides are in store.
With a lot of summer growth and leaves on the trees, there will be some branches down and scattered power outages.

___________________________________-

Atmospheric Sciences 101

Like last year, I am teaching atmospheric sciences 101:  a general introduction to weather and climate, this fall.  You can learn more about the class on the class website.  I talk about everything from the basics of the atmosphere, to weather prediction, thunderstorms, hurricanes, and local weather to global warming and climate.

I will be teaching the class in person at the UW, but will also make it available over zoom.  Thus, folks can take it remotely.

If you are over 60, you can take the class through the ACCESS program for a very nominal charge (something like $15).   Last year I had over 125 folks do so.

So if you are a UW student looking to learn about weather or a non-student interested in the topic, I welcome you to join me this fall.


September 15, 2021

Heavy Rain and Rapidly Rising Rivers: The Details on the Friday/Saturday Inundation

If you were planning to take a hike on Friday, forget it.  Thinking about painting your house?  No way.

It is going to be very, very wet on Friday and early Saturday, and I suspect some daily precipitation records will be broken.

But let me give you the details.

Let's start by showing you the latest accumulated precipitation totals forecast by the European Center model for the period ending 5 PM Sunday.  Virtually all of the mountainous areas of the region will get more than 2 inches, with some being hit by 5 or more (particularly the Olympics and North Cascades).


The UW forecast model, driven by the U.S. GFS global model,  for the period ending 5 PM Saturday, has a similar distribution. 3-5 inches in the mountains will be extensive, with some "favored" areas being wetted by 5-7 inches.


How much confidence should you have in this forecast?  An important question.

We are close enough in time, that the models should be relatively locked on to the correct solution, but as I have discussed many times, the best way to get at uncertainty is to look at ensembles of many forecasts, each slightly different.

So take a look at the fancy presentation of the ensemble precipitation forecast from the top-of-the-line European Center ensemble system (below).  You are looking at accumulated precipitation at SeaTac Airport over time (time increasing to the right).

The average of all the ensemble members is shown by the green line and the extreme range of the forecasts (the highest and lowest forecasts) is shown by the brackets.  The blue boxes show you the forecasts that encompass the forecasts relatively close to the median (the median is the value in which half the forecasts are greater, half are less).


Wow... an amazing forecast, with the ensemble going for around three inches over the entire period.   

Considering that the average MONTHLY rainfall at Seattle is about 1.6 inches, that is a lot.   The spread of the forecasts is relatively small for the big wet day (Friday)...so there is great confidence that Seattle is going to be very, very moist.

The rain shield will arrive in the western interior around sunrise Friday and the heavy rain will extend into Saturday morning.  Cool and showery over the weekend.

Now let me emphasize that there will be considerable horizontal variation in the rainfall.  To show you this better, here are the high-resolution forecasts by the UW model of total precipitation for the 48-h ending at 5 AM Saturday.


Lighter amounts (less than an inch) to the northeast of the Olympics..that is the rainshadow effect to the lee (downstream) of the high terrain of that barrier. More rain south of Seattle than north of the city.  Big increases on the windward side of the Cascades...and, of course, less rain to the east of the Cascade crest.

So head to Port Townsend or southern Whidbey Island if you want to escape the worst of it.

The moisture that will hit on Friday is already streaming towards us from the western Pacific (see arrows in the latest water vapor satellite imagery below).


Two more days, it will be here.

The impacts of the precipitation on our rivers will be profound. 

 Right now most of the west-side rivers are below normal to normal.   But they all will be above normal by Sunday.  

To illustrate, here are the current and predicted flows from the NOAA/NWS River Forecast Center for the Snoqualmie River at Snoqualmie Falls.   HUGE, rapid rise to near-record levels.  The falls will be quite a sight on Sunday.  And you can get a nice breakfast there as well.


Finally, some historic context.  Below is a plot of the record daily precipitation amounts for SeaTac Airport.  Middle to late September has had some big events, reaching about 1.5 inches.  And I suspect most are like this one.....tapping significant moisture from the western Pacific.


Enjoy the change....and make sure your umbrellas are handy.  And I didn't even get to the issue of strong winds.   Next blog.

September 14, 2021

The First Heavy Rain Event of the Season

Everything is going to change on Friday.

You know change is in the air when the National Weather Service starts warning of clogged drains and gutters, and localized debris flows.

Consider the European Center model forecast for accumulated rainfall through Sunday at 5 PM (see below).  

Mama Mia!  2-4 inches in the mountains and .5-1 inch in the lowlands of Oregon and Washington.  Even eastern Washington gets some decent rain.


The UW model precipitation is similar. Note how regional extensive the rain is, including east of the Cascade crest. This is the storm we have been waiting for.



The heavy rain will occur mainly on Friday and early Saturday.  If you were planning on putting in some plants or planting grass seed.....this is the time to do it!

This rain will mark the end of the wildfire season in the Northwest, the remaining fires will rapidly decline with the massive moisture, high relative humidity, and MUCH lower temperatures, with highs dropping into the lower 60s.

Snow, YES SNOW, above 6000 ft.

The reason for this change is the development of a strong trough of low pressure over the northeast Pacific, with a powerful jet stream of strong winds to its south.  

Here is the forecast for roughly 30,000 ft at 11 AM on Friday.  The yellow colors show you the strong jet stream winds.... coming right into the Northwest.  Some as strong as 150 mph.   The solid lines are heights (think of them as pressure).  The low center is due west of British Columbia. 

This is a very favorable pattern for heavy rain in our region.


This jet stream of strong winds is associated with a very moist plume of moisture that will drive into our region and rise over the mountains, releasing huge quantities of water. 

To illustrate, here is a graphic for 11 AM Thursday showing something called Integrated Water Vapor Transport (IVT), a measure of how much water vapor is being moved horizontally by the winds.  Blue indicates very high values.  Just drop a mention of IVT when talking to your friends...they will be impressed.


And the latest forecast model runs have a lot more coming after this.  If you were Noah, you would know what to do (see below).    Ironically, with all the talk of drought, our region could end up with near-normal summer and annual rainfall total before the month is over.  The water is well-timed for the upcoming salmon spawning season.




September 12, 2021

The Malden Wildfire and Climate Change: Why are Major Media and Politicians Distorting the Truth?

If the nation and world are going to deal with climate change, it is essential that the public is given accurate information.

Unfortunately, a number of media outlets (e.g., the Seattle Times and NPR), politicians, and activist groups are consistently distorting the truth.   There are few better examples of this problematic behavior than claims that the wildfire that destroyed the eastern Washington town of Malden in September 2020 was the result of climate change.

This blog will provide you with facts based on data, peer-reviewed papers, and government reports.  You can decide whether some folks are misinforming you.


The Claims

During the past year, a number of media outlets, politicians, and climate activist groups have made unfounded claims that the Malden/Babb fire, which destroyed the town of Malden (roughly 30 miles south of Spokane) was the result of human-induced global warming.

For example, last week the Seattle Times did a long story on the Malden fire and concluded.


National Public Radio, including local NPR station KNKX, did a story with the suggestion that the fires were the result of "global warming hitting us hard."


And then there is our governor, who claimed the Malden conflagration was a "climate fire"


“ I think we need to start thinking about this as a climate fire because that’s what makes them so explosive.”

I could give you a dozen other examples of such claims about the Malden Fire and climate. 

 These claims are unfounded and this blog will provide you with the facts.  

The Malden/Babb Fire Event

The Malden fire ignited around noon on September 7, 2020, was long and narrow, and moved within hours from its ignition point southwestward across the towns of Malden and Pine City (see map).

Fact 1:  The Malden Fire was a grass and bush fire.  Trees did not supply significant fuel.

The route of the fire, in arid eastern Washington. was nearly entirely grass, wheat fields, and small bushes.   Isolated trees were not a significant fuel source of the fire and most of them remained green after the fires.  A satellite image of the path is shown below (GoogleEarth Pro).


An image from GoogleMaps from PineCity/Malden Road gives you a first-hand view of the kind of vegetation the fire traversed.

Grasses and small diameter fuels are easily ignited, dry quickly, and can produce flashy, fast-moving fires when there are strong winds:  ALL of these factors were elements of the Malden fire.

Fact 2:  The fire was started by a tree, blown by strong winds, hitting a transmission line, creating sparks that ignited grass below.  

This was the conclusion of the official WA State Department of Natural Resources report.  An image of the tree and the power line is shown below.   Note that the tree is STILL GREEN.  Stunningly, DNR found that that tree had hit the powerline before, with multiple scars on the tree branch that caused the fire.


Fact 3:  Unusually strong winds played a critical role in the fire

Not only did the winds start the fire, but winds rapidly drove the fire to the southwest.  The strong winds, which were very dry, further dryed the surface fuels and provided lots of oxygen for fire growth.

The winds that day around Malden were extraordinary in strength, with gusts from the north to northeast reaching 30-50 mph, something indicated by the winds at the nearby Escure RAWS station, about 25 miles downwind of Malden (see below).


Climatological data suggested that the low-level northeasterly winds that day were extremely unusual, if not unprecedented.  Support for this statement is found in a peer-reviewed paper I wrote with others that was accepted in the American Meteorological Society journal Weather and Forecasting.

Why Global Warming/Climate Change Had No Role in the Malden Fire

This is easy to demonstrate.  

The grasses and other light fuels around Malden are always dry enough to burn by mid-summer.  This has always been true and has nothing to do with climate change.  Eastern Washington has warm, dry summers and seasonal grasses dry out each warm season. 

Below are the 10-h dead fuel moisture (small diameter fuels than can dry within 10 hours) for summers of 2020 and ten years ago (2011).  The fuel moisture dries out over the summer to under 10%.



And my peer-reviewed paper  documents that the 10-h dead fuel moisture was NOT unusual right before the event (graphic from the paper below showing Columbia Basin fuel moisture conditions).  Very typical.


Fire danger from light fuels is greatly reduced when the 10-h dead fuel moisture is above 20%, but there is great danger below 10%, which was evident in September 2020 and is typical for late summer.  

Once you are dry enough to burn readily, you are dry enough to burn.  A bit warmer or drier conditions during the normally hot/dry eastern WA summers will have little impact.  A real weakness of the global warming arguments.

But there is more.   Light fuels, like grasses, dry very quickly under dry, windy conditions.  That is why grasses and small bushes are called 1-h and 10-h fuels.   The Malden fire was preceded by exceptionally strong dry winds.    


So even if the fuels had been wet before the event, they would have become sufficiently dry to burn due to the strong winds that day. The preceding weather and climate conditions were not relevant.

Even More Reasons Why Global Warming Had Nothing to Do with the Malden Fire

The extraordinary strong, dry northeasterly winds were key for initiating and spreading the Malden fire. And such winds will dry light fuels even if they were wet before

It turns out that global warming/climate change will probably WEAKEN such strong offshore-directed winds, because the strong winds during late summer/early fall are generally associated with COLD high pressure in the interior, and global warming preferentially warms the interior of the continent.  Such warming weakens the high pressure and thus lessening the strong northeasterly winds.  I have been working on this issue, with funding from the Amazon Catalyst project and NSF (see graphic below)

Climate models also suggest the potential for more convective showers in eastern Washington under global warming.

So global warming/climate change may lessen the chances for such fires, NOT increase them.  You won't read that in the Seattle Times.

Regional Climate Simulations Indicate Weakening Easterly Winds 
over the Region Under Global Warming


The Bottom Line

Major media like the Seattle Times and National Public Radio, as well as some local politicians, have claimed that the Malden Fire was caused by or made more likely by global warming/climate change.  

This is not true and they are doing substantial damage by blaming global warming and not calling for taking concrete steps to ensure that Malden disasters don't happen again.

The Malden Disaster Was Preventable

Instead of blaming global warming/climate change, there are concrete steps that could have prevented this tragedy.

First, trees near powerlines need to be trimmed so branches don't touch or fall on energized circuits.  Clearly, this was not done for this case.   Considering the limited trees of the region, it should not be hard to do so.  Furthermore, if the powerlines are not properly maintained, at least depower the lines during the very limited periods of strong winds.   The winds were well predicted ahead of time for this event.

Courtesy, First Energy Corp

Second, homeowners must create defensible spaces around their homes, without vegetation and debris.  Using google maps, one can view the conditions around the homes in Malden before the disaster.  Many, if not most, had no defensible space, with vegetation and grass immediately around the homes.  And homes can be built to better withstand fires, including non-flammable roofs, screens to prevent embers from entering roof spaces, and more.


Malden before the fire.

A Plea.  

Please no name-calling.  Every time I write blogs like this on climate change,  I get angry messages from activists, calling me a slew of names, with accusations that I am receiving funding from oil companies (I am not), and worse.  The Seattle Times did a hit piece on me in August in reaction to my blogs about the heatwave and my criticism of their continual transition to advocacy journalism.  And activist scientists like Michael Mann and Gavin Schmidt make nasty tweets.

I am as concerned about global warming as any rational person, but we need to start with facts and not hype and exaggeration.

If you are unhappy with the blog, TELL ME WHAT I HAVE GOTTEN WRONG TECHNICALLY.


Big Winds, Heavy Rain, and Now Thunderstorms

  Nearly 100,000  Washington State  power  customers lost power last night as strong winds first hit Northwest Washington and then spread ac...