October 19, 2021

Saving California

 California has experienced a very dry year, with the precipitation since January 1st well below normal in most of the state, with particularly dry conditions in the northern portion where several of the big reservoirs are located. Some areas are down as much as 15-20 inches!



And not surprisingly the reservoirs are generally quite low right now,  with a number down to roughly 35-40% of normal (see below).   Not good.

Making the situation more worrisome, a La Nina is a near certainty for this winter, which generally produces drier than normal conditions over central and southern CA.

But sometimes the atmosphere does not follow persistence or the expected playbook, and at least for the next week, the northern part of the Golden State is going to be hit hard with rain.  It may be called the Sodden State.

To give you some insight into this situation, below is the latest ensemble forecast from the highly skillful European Center modeling system fortotal precipitation over the western U.S. for the next 15 days.

Wow.  Not only is BC and Washington wet, but northern CA gets as much as 12-14 inches.  That would make a huge difference, helping to refill the reservoirs.


And the UW WRF model prediction of total precipitation for the next week is also wet with huge amounts over the Sierra Nevada and northern CA.


Not satisfied?  The 46 day precipitation anomaly forecast (the difference from normal) through December 3 shows a MUCH wetter than normal autumn over northern CA.


Now if they only would stop wasting water in agriculture (like 1 gallon used PER ALMOND), the water situation might stabilize down there.

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And I know you are curious about our big storm offshore.  It is still coming to our offshore waters on Thursday.  Here is the latest forecast from the European Center for Thursday morning.  Around a 955 hPa low.  Impressive

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The Second Edition of My Northwest Weather Book is Now Available!

My new book is greatly improved and expanded over the first edition, with new chapters on the meteorology of Northwest wildfires and the weather of British Columbia.  A completely revamped chapter on the effects of global warming on our region.  And it has been brought up to date with recent weather events and the imagery is improved greatly.
 

Where can you get it?

Local bookstores, such as the University of Washington bookstore.  The UW Bookstore has just received several dozen copies.

Or secure a copy from the publisher:  UW Press.

Or Third Place Books in Lake Forest Park or Seattle.

And yes, there are online sellers like Amazon and Barnes and Noble.





October 17, 2021

A Superstorm of Tropical Origin Will Develop Off the Northwest Coast on Thursday

 I have been watching this storm for a while, and I am now certain enough to tell you about it.

A powerful, unusually deep storm will develop off the Northwest coast on Thursday.

A mid-latitude cyclone that began as a tropical storm (Namtheun), now over the western Pacific.

Below is the 96-hour forecast valid at 5 AM Thursday (PDT) of sea level pressure from the U.S. NOAA/GFS model.   The solid lines are isobars (lines of constant sea level pressure).

Amazing...the storm, located due west of our coast, has a central pressure is 952 hPa, which is very, very low for a mid-latitude cyclone at our latitude.  

This storm is deeper (lower pressure) than the extreme Columbus Day storm of October 12, 1962--the greatest storm to hit the Northwest in 100 years or more.


The highly skillful European Center forecast at the same time (see below) is virtually the same, providing confidence in this prediction.


The simulated satellite image near the time of greatest strength is impressive, with frontal clouds swirling into the center of the low.  At that time, an associated from is making landfall on the BC and Northwest coastline.  Big storm.


As noted earlier, this strong, mid-latitude cyclone (low-pressure center) has its origins in Tropical Storm Namtheun, which is now many thousands of miles away (see visible satellite picture yesterday.)

It is a storm undergoing extratropical transition, changing both its structure and energy sources.   From deriving its energy from the warm waters of the tropical Pacific to the horizontal temperature differences of the midlatitudes.

The meteorological version of a hybrid car.  

Let me show you its path through a series of sea level pressure forecasts by the European Center model.  I put some black arrows in to show you the low center position.

Today at 5 PM...the low center is way over in the western Pacific.

5 AM Tuesday, it has moved northward and to the east

5 PM Wednesday, it has weakened, but is still identifiable, now in the central Pacific.


And by 5 PM Wednesday it has intensified rapidly and is now off our coast.


The storm revs up at an unimaginable pace on Wednesday and Thursday morning, deepening by 48 hPa in the 24h ending 5 AM Thursday.  This makes it a superbomb storm, with the term "bomb" used for storms that deepen by 24 hPa (a unit of pressure) in 24 hr.  This storm DOUBLES that...and does most of the amplification in 12 hr.   Stunning.

Fortunately for us, the storm is predicted to head northward away from the Northwest coast and to weaken as it moves into the Gulf of Alaska.....as suggested by the forecast for Thursday evening (shown below).


What about wind speeds?  The European Center surface wind gust forecasts for Thursday morning predicts around 80 mph near the low and even higher speeds in the coastal waters off northern British Columbia.    

Trust me...this is NOT the time to take an Alaska cruise.

And this storm will produce big waves, with the forecast significant wave heights for 5 PM Thursday reaching 30-35 ft.

The relatively short period of this quickly moving and amplifying storm is helping to keep the waves down to simply huge.

Truly major midlatitude cyclones reaching our shores are often associated with tropical disturbances originating in the western Pacific.  That is true of the great Columbus Day storm.   Tropical cyclones are frequent this time of the year and the jet stream is strong enough to supply needed energy and a fast ride to the east.

And don't forget that our big heatwave in late June could be traced to a tropical cyclone moving northward, causing big downstream waves to develop after it banged into the jet stream.

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The Second Edition of My Northwest Weather Book is Now Available!

My new book is greatly improved and expanded over the first edition, with new chapters on the meteorology of Northwest wildfires and the weather of British Columbia.  A completely revamped chapter on the effects of global warming on our region.  And it has been brought up to date with recent weather events and the imagery is improved greatly.
 

Where can you get it?

Local bookstores, such as the University of Washington bookstore.  The UW Bookstore has just received several dozen copies.

Or secure a copy from the publisher:  UW Press.

Or Third Place Books in Lake Forest Park or Seattle.

And yes, there are online sellers like Amazon and Barnes and Noble.








October 15, 2021

The Columbus Day Storm and Stormy Weather Ahead: All in My Latest Podcast!

This week marked the anniversary of the great Columbus Day Storm, which occurred on October 12, 1962.

Probably the most powerful non-tropical storm to hit the lower-48 states in 100 years.

Unpredicted the day before, the Columbus Day Storm brought gusts above 100 mph across the region, and the storm had a remarkable origin.

I provide the fascinating details about the storm in my podcast (see below)


But there is more.  My podcast begins with the latest weather forecast....and it is a mixed bag...with heavy rainfall over the Olympics and North Cascades over the weekend, and a strong front moving through Sunday morning.  Saturday will be the better day.

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



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Like the podcast? Support on Patreon Become a Patron!

October 13, 2021

A Cold, Snowy Start to Fall

 Fall so far has been much cooler and snowier than normal in the Northwest.

To "warm-up"  this discussion, take a look at the snow coverage at Crystal Mountain and at Mt. Baker Ski resort--enough to motivate a search for the hot chocolate mix.



A more quantitative view is provided by the NOAA snowpack analysis today (actually the snow-water-equivalent--the amount of water in the snowpack), compared against the last year (see below).  A lot more snow this year!




The temperature departure from normal over the past two weeks is chilling:  western Washington and Oregon have been much cooler than normal (by 3-6F).  So have much of the West.


And plotting the temperature at Sea-Tac versus the normal highs and lows over the past two weeks is startling: Only ONE day had a high temperature reaching the normal values and MANY days had low temps plunging well below the normal lows:


Yesterday morning, a number of western Washington stations dropped to freezing and below, and some low-temperature records were achieved (see below)


It looks like we will warm up a bit during the next few days, with a high in the mid-60s on Saturday, but then we slide back into the mid-50s (see European Center forecast for Seattle).  Sorry.     My zucchinis are dying and my tomatoes are remaining green.  Not good.



Depressingly, the latest European Center extended forecast for the next month is going colder than normal (blue colors).   You might find your sweaters.....






October 11, 2021

Aurora Occurring Tonight!

A significant solar event is occurring and an aurora is visible to the north over northern Washington State right now.

Here is a recent image from Greg Johnson's Skunk Bay Weather website:


And the latest NOAA Space Weather Aurora forecast for 11:30 PM shows the core of it just north of us.

NOAA's Space Weather Center had put out a geomagnetic solar storm watch, which has clearly verified.  Over the weekend a coronal mass ejection (CME)...or solar flare... erupted on the sun's surface and raced towards the earth.  The interactions of this ejection from the sun and the Earth's magnetic field resulted in the aurora, which was visible over the northern U.S. and Canada.


A measure of the amplitude of the solar event is the Kp index, which has reached a fairly high level of 6:



Do you want a real treat?  Here is a video of the aurora action from Skunk Bay:



The skies are generally clear over Washington and southern BC, so we are in a good situation to view the celestial show. A good opportunity.

October 10, 2021

The U.S. Could Have Wildfire Smoke Radar

Imagine the ability to determine the three-dimensional distribution of wildfire smoke across the United States in real-time.

We can see the spatial distribution of smoke from space but lack the detailed
 three-dimensional structure

Such a capability--let's call it smoke radar-- would improve weather prediction, because smoke influences temperature and clouds. 

A smoke radar would help protect human health by assisting in the prediction of the future distribution of smoke near the surface.  Air quality forecasting would be improved. 

Smoke radar could enhance aircraft safety 

And a smoke radar would be a potent tool for research, from diffusion studies to climate change.

Best of all, the National Weather Service already has the hardware in place, but simply needs to find the funds to collect the data.  And for a modest additional investment, the current units could be upgraded to dramatically improve their capabilities.

The Opportunity

The National Weather Service and the Federal Aviation Administrations have weather observation equipment at every major and minor airport across the U.S. (see map).  Roughly 1000 of them.

Called the Automatic Surface Observing System (ASOS), this collection of instruments includes all the expected parameters (e.g, temperatures, wind, humidity, and precipitation) but also includes a device called a ceilometer that can measure the height of the bases of clouds.   

The currently installed ceilometer (the Vaisala CL31, see below) has a laser that sends out light pulses that are reflected and scattered back to the ground by clouds and other atmospheric features.  By timing the pulses and measuring the amount of return, the location and relative density of the target can be determined.


The Vasailla Ceilometer can see targets as high as 25,000 ft, although the National Weather Service only uses its capabilities over the lower 12,000 ft.

But now the exciting thing.  These ceilometers can sense wildfire smoke and penetrate thin to moderate smoke to see smoke layers aloft.    Here is an example from Tacoma earlier this year.  In essence, this device is a smoke radar for the atmosphere above the unit.  And there are enough of them across the U.S. to provide a detailed three-dimensional description of wildfire smoke (and clouds) around the nation.

But the tragedy of it all is that this data is never leaving the devices.   The National Weather Service lacks the communication infrastructure to get this valuable data off the ceilometers, to collect it at a central site, and then to distribute it to eager users.

It is estimated that this would cost approximately 3 million dollars, a very small sum considering the huge value of the information.

But there is more.   The current ceilometers (CL31) represent old technology and Vaisala has a vastly more capable unit (the CL51) that could provide greatly improved smoke information...both in detail and in vertical extent.   

A sample is shown below. Wow.  Really impressive detail.

All the ceilometers in the U.S. could be upgraded for approximately 30 million dollars, a modest investment for such a powerful tool.

A number of U.S. scientific groups have advocated this investment. For example, in 2012, the Thermodynamic Profiling Technologies Workshop (Hoff et al., 2012) recommended that the ASOS network be better leveraged to obtain this data.  Here in the Northwest, a group of air quality agencies, under the leadership of Dr. Phil Swartzendruber of the Puget Sound Clean Air Agency, has advocated for acqur=iring ceilometer smoke information from ASOS.

An Example of the Use of Ceilometer Smoke Information

I personally use ceilometer data during the smoke season for predicting changes in surface air quality.... and my colleagues at Puget Sound Clean Air Agency (PSCAA) do as well.  Both the University of Washington and PSCAA have their own ceilometers.   During last summer,  there were mornings that the ceilometers showed smoke a few thousand feet above the surface, but the air quality was good near the ground.  But we knew that the heated surface would cause vertical mixing (like in your heated cereal pot) and that mixing would bring the smoke down to the surface causing degraded air quality.

It happened, just as expected.  Do I like ceilometers!


These days, there is a lot of talk about upgrading U.S. infrastructure.   With all the concern about wildfire smoke, smoke radar from ceilometers should be high on the list.  And we are fortunate to have a well-placed Senator, Maria Cantwell, who chairs the committee that oversees NOAA and the National Weather Service.

The CL51

Senator Cantwell played an extraordinary role in securing the acquisition of the Langley Hill Radar near Hoquiam, which greatly enhanced weather prediction and heavy precipitation in our region.  Maybe she can do her magic again with the ceilometers.

October 08, 2021

Why are Cloud Bases Often Flat While the Tops Are Variable? Plus, My New Podcast on Relative Humidity Versus Dew Point

Everyone cares about moisture in the atmosphere, which controls our comfort and much more.   Often we call this humidity.

On TV and the media, there are two measures of humidity that are frequently provided:  relative humidity and dew point.

They are very different parameters and in my Podcast, I tell you exactly what they are and how you can use them.  Plus, the weekend forecast.

Listen here or through your favorite podcast server

And talking of moisture in the atmosphere, have you ever noticed that when the sky is full of cumulus clouds, the base of the clouds is often flat, while the tops are irregular and corrugated? 

Here is a picture I took on Wednesday.  


And here is another.


 
Why is this strange situation occurring over and over again?  Why are such cloud bases flat?

Let me explain!

Clouds, like the cumulus clouds shown above, are associated with rising air.

This air starts with a certain amount of moisture but is not saturated--the relative humidity is less than 100% (check my podcast to learn more about saturated air!).  

To understand flat cloud bottoms, there are TWO things you have to know:

  1. Rising air cools.  It cools because it is going from higher pressure near the ground to lower pressure aloft, which results in the air expanding...and it takes energy to expand.   Ever let the air out of a pressurized bicycle or car tire?  It is cool!
  2. The amount of moisture air can hold depends on temperature.  Warm air can hold more water vapor than cool air.  Thus, the ascending air can hold less and less water vapor as it rises.

Eventually, the rising air cools to saturation (100%) relative humidity and at that point, water vapor condenses into little cloud droplets.  The bottom of the cloud forms.

If the rising air is of relatively uniform temperature and moisture and the vertical motion is also relatively uniform (which is often true on the scale of a cumulus cloud), the rising air will reach saturation about the same level,  producing a flat cloud base.

The top of the cloud does not have to be as uniform.  Vertical instability or convection within the cloud can be very sensitive to small differences in temperature and humidity, producing varying heights of cumulus turrets projecting upwards.  

In any case, the result is the typical cauliflower shapes of the upper portions of cumulus clouds.    

So flat bottoms and varying tops are typical...and now you know why!

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


Some major podcast servers:

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Saving California

 California has experienced a very dry year, with the precipitation since January 1st well below normal in most of the state, with particula...