Tuesday, April 30, 2019

Wetter than Normal April to be Followed by a Very Dry Start to May

It is not unusual to have a very dry period sometime during the first half of May....and this year won't disappoint.   Particularly, after April ended up wetter than normal over the Northwest.

The precipitation departure from normal over the western U.S for the past 30 days, shows that most of Washington and Oregon enjoyed above-normal precipitation last month (green and blue colors)


Seatttle-Tacoma Airport, for example, ended up with about an inch above normal (purple is observed, cyan is normal in the figure below)


But there will not be any rainfall for many days now due to the development of a major ridge of high pressure over the eastern Pacific.

The UW model shows dry conditions during the next week over most of the Northwest, with the exception of  a few light showers over the north Cascades.  More rain in California.


The origin of this dry bounty?  A very persistent ridge of high pressure over the eastern Pacific.  Here is the forecast upper level map (500 hPa, about 18,000 ft) for Friday evening.  Major ridge over the eastern Pacific, with a low center to the south.   This is called a REX BLOCK and is very, very stable.


The situation Tuesday afternoon still shows a ridge of high pressure/heights along our coast.


Better get use to temperatures in the mid to upper 60s.

Sunday, April 28, 2019

The Meteorology of the Seattle Crane Collapse

Important New Information:  An unofficial report from the weather station at the very close Center for Wooden Boats noted a gust to 35 mph at 3:26 PM on Saturday.
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A crane collapsed in Seattle around 3:30 PM yesterday (Saturday) at the site of the new Google facility (Fairview and Mercer).  Tragically, four people lost their lives and several more were injured.


The failure was coincident with the passage of a wind shift and surge in winds associated with the southward passage of a Puget Sound convergence zone.   This wind shift/strengthining was associated with a dark cloud feature and some light rain...something that was evident from a sequence of images from the Seattle PanoCam ( a sequence from 3:10 through 3:40 PM is shown below).




The weather radar image from Camano Isl at 3:26 PM showed light to moderate precipitation associated with the convergence zone.

While the Doppler radar velocity indicted a strengthening of the wind (gray color indicates little velocity towards or away from the radar, the light yellow about 20 kt).


One of the nearest observing sites was near Eastlake Ave. (see map--the oval is the accident site)


 The observations at this site showed a gust to 25 mph just at the time of the incident.  The winds were from the north.  Look at the temperature trace (red line).  There was a large (roughly 10F) drop)in temperature with the wind event--consistent with the increase in clouds and onset of precipitation (note that the dew point (green line) rose at the same time, consistent with a moistening of the air).

Even better perhaps was a site right on the lake (see map)..


Its winds gusted to 23 mph around 3:30 PM.


Other nearby sites were consistent with this wind evolution, but slightly weaker.  The site in question could have had stronger winds (5-10 mph more) because it was upstream of the relatively smooth/low drag Lake Union.

The development of strong northerly winds on Saturday afternoon was expected, with the model and NWS forecasts clearly predicting it (see sample below).  Seattle WindWatch was sending out messages for days.
I will let others evaluate whether an increase in winds to around 30 mph should have taken down the crane.

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The Northwest Weather Workshop on May 3-4



There is one local gathering each year in which regional meteorologists and interested layman get together to talk about our weather and its impacts:  the Northwest Weather Workshop.  This meeting is open to everyone.

The workshop this year will be on May 3-4 at the NOAA/NWS Sand Point facility in north Seattle.


The first day will include a session on Northwest wildfires--their prediction, the smoke, the associated meteorology and more.    That evening there will be banquet and a special speaker from Washington Department of Transportation, talking about dealing with the cold and snow in February.  Saturday will have sessions on OLYMPEX (a weather field experiment in the Olympics),  advancing weather modeling, the cold/snow of February, and much more.  Lunch Saturday is included in the modest registration fee.  There are special rates for students.

Typically, about 120-150 folks attend the meeting, which is held in Bldg. 9 of the NOAA Sand Point facility just north of Magnusson Park.  Folks often want to know where you have to be a meteorologist to come.   My answer is that 70-80% of the talks should be perfectly accessible to lay people.

You can view the detailed agenda here.  If you want to go to the meeting you must register in advance.  To register or learn more about the workshop, please go to this website: https://atmos.washington.edu/pnww/

Saturday, April 27, 2019

Strong Winds Descend into Eastern Washington

A frequent springtime weather feature of eastern Washington is the tendency to get strong northeasterly winds--sometimes with blowing dust.

And such strong winds are occurring right now.    Here are the maximum gusts since midnight (click to expand).  Several locations, from near Wenatchee to Yakima, are gusting to near 50 mph from the northeast.  Strong winds in the Strait of Juan de Fuca as well.


A close up gives you a better view....59 mph just just of Lake Chelan and 61 mph near Blewett Pass...with strong winds extending out into the Columbia Basin. 50 mph at some high elevation locations, such as near Snoqualmie Pass and 80 mph at White Pass.


 The reason for all this?  The passage of an upper level trough from the Northwest, resulting a a very large pressure gradient that is consistent with northwesterly winds in the lower atmosphere.  Here is the forecast weather map at 850 hPa (about 5000 ft) showing heights and winds at that level.  Strong northwesterly winds aloft!


And when those winds interact with the Cascades they are strengthened over  the eastern slopes--something called mountain wave amplification.  To illustrate, here is the wind gust forecast of the UW WRF model for 11 AM this morning.   The blue colors are 45 kt or more....the model was certainly going for the strong winds.


Northwesterly winds are also producing a very active Puget Sound Convergence zone, as air moving off the Pacific is deflected around the Olympics and converges over the Sound.




The National Weather Service had wind warnings out for this event  even yesterday (see below)


and among the issues they warned about was raising dust...which has occurred in some locations (like a location just east of Spokane)--see below.


Things should quiet down tomorrow.... and a sunny, dry day beckons..

Thursday, April 25, 2019

Is Washington State Air Quality Getting Better or Worse?

Has air quality in Washington State gotten better or worse during the past 15  years?  

The answer:  generally better except during wildfire smoke periods during the summer.

Let me show you the data.  I started at a wonderful web site run by the Puget Sound Clean Air Agency that allows one to plot all kinds of air quality indices.   I plotted PM2.5 concentrations--the concentrations of particles below 2.5 microns (millionths of a meter).  These particles are the kind that can move deep into your lungs, causing all kinds of problems.  And high concentrations are associated with poor visibility.

Here is the plot of maximum daily values in Seattle from August 2001 to yesterday.  The vertical lines are on January 1st of each year.  The first thing you notice is that August 2018 had the biggest peak on record (about 150)--that was the terribly smoky period of August 21-22.   Next came the wildfire smoke period in 2017. 


Look closer and you will notice that earlier in the period, the worst air pollution was generally during the winter--often when we had high pressure and low-level inversions.  The source of the pollutants were mainly from combustion (trucks, cars, ships) and wood-burning in stoves and fireplaces.

Look even closer and you will notice that the pollution levels were generally HIGHER earlier in the century.   So our air has gotten generally better except for some wildfire spikes during summer. 

A good way to see this is to plot the monthly small particle values at Seattle (below).  The general levels are clearly lower after approximately 2007, with the sole exceptions of two summer months in 2017 and 2018....which included the few days of wildfire smoke in Seattle.


The annual average concentrations, which include everything, suggest a similar pattern, including a minimum during the economic slowdown in 2008!  Less trucks and cars on the road, I assume. 

Even with the wildfire smoke incidents, our air is overall better now than before 2007.  As Mr. Spock would say...fascinating.


What about Spokane, in the eastern part of our state?  A similar story.  They had an additional wildfire smoke spike in 2015 (a big year for wildfires).    They are closer to more of the wildfire sites than Seattle.


Spokane's monthly pattern is similar--general improvement over the years except for the transient smoke periods during summer.  But their annual amounts (not shown) have gotten worse because they are more exposed to the summer wildfire smoke.


An excellent paper examining this issue was completed by Dr. Crystal McClure and Professor Dan Jaffe of UW Bothell.  They compared the trends of small particles in the air for the Pacific Northwest and the rest of the country and plotted this (see below) for various concentrations (that is what the quantile business is below....the high concentrations are in the high quantiles) 

For the rest of the U.S. the particles are declining at ALL concentrations.   But this is NOT true for the Northwest!   We ARE getting better for low and moderate concentrations of particles, but are having more days of the HIGHEST concentrations--that is the influence of the wildfires.


They even plotted a map of the change in the trend of very large concentrations of small particles (the top 2%  each year) for 1988-2016, which is shown below (note they did not include 2017 and 2018).   Most of the nation has shown a decline in high concentrations of the small particles (blue and green colors), except for a broad area of the Northwest, where increased wildfire smoke is having an impact.

Finally, why is our air quality getting much better, with the exceptions of the summer wildfires? I talked this over with Eric Saganic, an air quality expert at Puget Sound Clean Air Agency.   He told me there are several reasons: 

1.   Trucks have become MUCH cleaner (starting around 2007-2008), with new ones emitting about 1/50th the amount of particulates.
2.    Car emissions have declined as gas mileage has improved, more hybrid vehicles have hit the road, and engine technology has been enhanced.
3.   Ships in our harbor are using much cleaner, lower-sulfur fuels
4.  Wood burning for heat has declined and wood stoves have improved.
5.  More aggressive and effective burn bans by his organization and others when poor air quality situations threaten.

A huge advance in cleaning our air. 

Be we have to deal with the wildfire smoke, which means making the investments in dealing with our disastrously mismanaged forests east of the Cascade crest that have become overgrown and susceptible to large catastrophic fires due to nearly a century of fire suppression.  That means thinning, select harvesting, and prescribed fires during the spring and autumn to clear out the small stuff.  Such forest management has been terribly underfunded during the past decades, but some folks in DNR are starting to talk about it seriously.   It is time for an aggressive program to restore our forests to be like they were 150 years ago, which frequent fires east of the Cascades crest were the rule.


Monday, April 22, 2019

A Subtlety of Local Weather

As with great wine, Northwest weather has its subtleties, some of which are interesting or even beautiful in their own way, even if they don't produce severe or exciting weather.

Yesterday was a good example.   Below is the high resolution NASA MODIS imagery around noon Sunday that was centered on the Olympic Mountains.

Do you see the the ring of low clouds around the Olympics?   And some of that rink of clouds extends northeast of the Olympics.   Why does it exist?  

As an aside, over the high, central Olympics you can see the dendritic pattern of snow on high terrain.  Snow is also obvious on the higher ridges of the Cascades, with Mt. Rainier in the lower, right corner.  The Pacific is covered with low clouds, with plenty of low, broken clouds pushing into western WA.

A suggestion of what may be going on is found from the surface winds around the same time as the image.   There is weak southwesterly flow approaching the Olympics along the coast, with cool cloudy air moving eastward into the Strait of Juan de Fuca to the north and south of the Olympics across Shelton and Bellingham (KSHN and KPWT).

But look closely.  To the southeast and northeast of the Olympics, there is air moving TOWARDS the Olympics.  This is important.


The flow at 850 hPa (about 5000 ft) at the same time shows westerly flow approaching the Olympics and being deflected by the roughly circulation barrier.


And the forecast relative humidity at the same time at the same level  shows a ring of high values (lighter shading) surrounding the Olympics--this looks a lot like the ring of clouds shown in the satellite picture.



Now let's look at the surface winds and sea level pressure (brown lines) forecast by the UW WRF model at 1 PM Sunday.  Pressure was relatively lower in the Olympics and higher in the cool, dense marine air circling around the barrier.  Look real close and you will see upslope flow (air moving towards the high Olympics) at low levels in a ring around the barrier.    That upslope flow produced additional cooling the enhanced the low clouds and also made them deeper in the ring around the mountain barrier.

That was the origin of the ring.




But with our fancy, high resolution models we can do much more.  We have full three-dimensional data, like a 3D meteorological CAT-scan.    Let's do a vertical cut or cross section SW-NE across the Olympics (see below) at 11 AM Sunday.  Clouds are shown by the color shading.  You can see the ring.  Winds in the cross section are shown by the wind arrows.  Relative humidity by the red lines and the blue lines are temperature (something called potential temperature).

Aloft, some air was moving up and down the upper slopes of the Olympics, with enhanced downward flow on the NE side of the Olympics contributing to lower pressure there.  But you can see the tongues of cooler, cloudy air rising on both sides of the Olympics, particularly on the NE side.


So we had weak, flow coming off the Pacific from the west and southwest; this cool, cloudy air pushed around the barrier.   A difference in low-level pressure between relatively high pressure in the cold, dense cloudy air and lower pressure produced by downslope flow on the barrier, helped generate upslope flow for the north to southeast quadrants of the barrier.  Just plain upslope flow was observed on the southwest side of the barrier.

A subtlety perhaps.  But for connoisseurs of local weather, an example of the kind of fine detail that our modern tools can reveal.


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The Northwest Weather Workshop on May 3-4

There is one local gathering each year in which regional meteorologists and interested layman get together to talk about our weather and its impacts:  the Northwest Weather Workshop.  This meeting is open to everyone.

The workshop this year will be on May 3-4 at the NOAA/NWS Sand Point facility in north Seattle.


The first day will include a session on Northwest wildfires--their prediction, the smoke, the associated meteorology and more.    That evening there will be banquet and a special speaker from Washington Department of Transportation, talking about dealing with the cold and snow in February.  Saturday will have sessions on OLYMPEX (a weather field experiment in the Olympics),  advancing weather modeling, the cold/snow of February, and much more.  Lunch Saturday is included in the modest registration fee.  There are special rates for students.

Typically, about 120-150 folks attend the meeting, which is held in Bldg. 9 of the NOAA Sand Point facility just north of Magnusson Park.  Folks often want to know where you have to be a meteorologist to come.   My answer is that 70-80% of the talks should be perfectly accessible to lay people.

You can view the detailed agenda here.  If you want to go to the meeting you must register in advance.  To register or learn more about the workshop, please go to this website: https://atmos.washington.edu/pnww/



Friday, April 19, 2019

A Very Nice Holiday Weekend

This is a special weekend, including both Easter and Passover celebrations.   And we are in the midst of a rapid transition in our surrounding vegetation, with trees leafing rapidly, blossom's blooming, and time to think seriously about gardening.

So weather is important.   And it won't disappoint.

Friday was a dreary dark day for most of us, as a frontal band sat over the region most of the day.

Visible satellite imagery at 1 PM Friday.

Fortunately,  a modest ridge of high pressure will move over us on Saturday, ending all precipitation and resulting in partly cloudy skies (see image of upper level heights at 500 hPa...about 18,000 ft...below ).   Highs will get up to around 60F.



An important issue for all gardeners is that the soil temperatures are progressively warming.  The WSU AgWeather  Network shows that the 8 inch soil temperatures in western WA are all in the 50s, and here in Seattle the soil temperature are above 55F--warm enough to start thinking about lawn seeds and perhaps beans/zucchini (see graphics below).  My pea seeds, planted two weeks ago, have all germinated and now push up through the soil.  Too soon for tomatoes, though.



By Sunday, the ridge will be weakening and increasing westerly flow will be moving in aloft.  Expect increasingly high cloudiness later during the day, but no rain (see upper level map at 2 PM Sunday).


And now an important point....eastern WA, which has been substantially cooler than normal for most of the past month, is finally warming up, with many locations in the Columbia Basin getting into the 70s this weekend.    Here is the forecast temperatures for 5 PM Sunday, showing the warming from Yakima to the Tri-Cities.  Good for agriculture.


In short, a great weekend to do anything you like outdoors and welcome warmth east of the Cascade crest.   There is only one thing to worry about....the pollen count.  Without rain removing pollen from the air and all the flowering plants, the pollen count is predicted to rise....sorry.



Wednesday, April 17, 2019

U.S. Numerical Weather Prediction: Darkest Before the Dawn?

U.S.  operational weather prediction is undergoing a rough patch right now, with a new global modeling system that is proving not quite ready for prime time.

But there is reason for hope.  A combination of new leadership and reorganization may turn things around during the next few years.  The old saying, it is darkest before the dawn, may well prove true for operational numerical weather prediction in NOAA and the National Weather Service.


As I have described in many previous blogs, the U.S. is lagging behind in operational global weather prediction.  Today and for many years, the U.S. global modeling system, the NOAA/ NWS GFS (Global Forecast System) model has trailed behind the world leader,  the European Center Model, and is consistently less skillful than the UKMET office model run by the British.  We are usually tied for third with the Canadian Model (CMC).   And we lag behind the others even though the U.S. has the largest meteorological research community in the world.

To illustrate the problems, here are the latest comparative statistics (anomaly correlations!) for the global skill of the 5-day forecast at 500 hPa (about 18,000 ft up) for a variety of models.  1 represents a perfect forecast.  The best forecast is the European Center (average of .915), next is the UKMET office (the British folks with a .897), third is the Canadians (CMC, .773), and FOURTH is the U.S. GFS (.869).


It is no secret why the GFS is behind:  an old model, inferior data assimilation and use of observational assets, and relatively primitive model physics (e.g., how cloud processes, thunderstorms, turbulence, etc. are described).  Inadequate computer resources contributed as well.  Data assimilation is the step in which a wide variety of observational data is quality controlled and used to create a  physically realistic three-dimensional description of the state of the atmosphere. The European Center does a very good job at this.

The inferiority of the U.S. global model has gotten a lot of press the last 6 years, particularly after the GFS showed itself to be clearly less skillful than the European Model for Hurricane Sandy.    The hue and cry in the media resulted in a computer upgrade for the National Weather Service and the acquisition of a new global model, the NOAA Geophysical Fluid Dynamics Lab (GFDL) FV3.  This new model has been running in parallel for nearly a year now.

But there are problems with the new FV3.  The FV3's verification scores are only slightly better than GFS, something shown in the statistics above (FV3 was at .881, in third place).  Part of the problem is that the FV3 is using the same data assimilation system as GFS, which is not as advanced as the one used by the European Center. 

But there is something else:  during the cold period of the past winter, the FV3 was predicting crazy, excessive snow amounts.  And more detailed verification indicated that the FV3 was too cold in the lower atmosphere.  Disturbingly, the NWS evaluation protocols were not able to delineate the problems previously.
Coastal California was predicted by FV3 to be snowbound in February,  It didn't happen.

The FV3 was supposed to go operational in January, but was delayed until February because of the government shut-down.   Then the snow/cold problem was revealed.   According to my contacts in NOAA, they have found some, but not all, of the problems.   At this point,  the operational implementation has been delayed indefinitely into the future.

In some ways, this is NOAA's version of the Boeing Max disaster --in the hope of beating the competition, a software system was rushed into operations without sufficient testing and evaluation.


Another major problem?    It appears that there aren't enough people inside the National Weather Service (NWS) who actually understand the new FV3 model.

FV3 was developed outside the NWS by a team under a very capable weather modeler, S. J. Linn, of the NOAA Geophysical Fluid Dynamics Lab.  In essence, the model was "thrown over the fence" to the Environmental Modeling Center (EMC) of the NWS and few people there actually understand FV3 in any depth.  About 3, according to my sources.  S. J. Linn has recently moved back to Taiwan and is no longer available. 

In addition to lacking depth of knowledge about the core FV3 modeling system, the NWS does not have much of an effort to improve the physics of the FV3, such as the microphysics that describes how clouds and precipitation processes work in the atmosphere.   Physics is one of the key deficiencies of the U.S. models.  And the data assimilation system was simply moved over from the inferior GFS.

But the situation is even worse than that.  FV3 was supposed to be a community modeling system, one that could easily be run outside of the National Weather Service, including the universities and private sector.   Having others use the model is essential:  instead of only a handful of folks inside the NWS working on and testing the model, you get hundreds or thousands doing so.  You end up with a much better prediction system that way.



But the NWS has put virtually no effort and resources into making FV3 a community modeling system, TWO YEARS after making the decision to use it.  I have tried myself to use the latest release.  There is no support, no tutorials, no help desk.  Nothing.  The code release is incomplete and poorly documented.  The model code is hardwired for NOAA computers and some of my department's most accomplished IT people can't get it to run.   Not good.

In contrast, the major U.S. competition to FV3, the NCAR MPAS (NCAR is a consortium of many of the atmospheric sciences departments in the U.S.), is easy to run and has lots of support.  One of my students got going on it in days.

The bottom line in all this is that the U.S. move to improved global prediction using FV3 is not going well. 

The NWS has made the right move to hold off on implementation until FV3 is at least as good as the old GFS, considering the critical role the U.S. global model plays in American weather prediction.

But the dawn still beckons...



Things are pretty dark for U.S. global prediction right now.  But there are some reasons for optimism.

First, the FV-3 is a better designed and more modern weather modeling system than the old GFS, including being more amendable to running on large numbers of processors.  It can be the basis for improvement.

Second, NOAA/NWS leadership accepts there are problems and wants to fix it. 

Of particular importance is that the key person responsible for U.S. operational prediction and observation, the Assistant Secretary of Commerce for Environmental Observation and Prediction and acting NOAA administrator, is Dr. Neal Jacobs, an extremely capable and experienced weather modeler, who led the successful effort at Panasonic before moving to NOAA.  Dr. Jacobs knows the issues and wants to deal with them.   Furthermore, there is a relatively new and highly capable head of the NOAA/NWS Environmental Modeling Center (where U.S. operational weather prediction takes place), Dr. Brian Gross.

Dr. Neil Jacobs is now acting Administrator of NOAA

Add to that the new Presidential Science Adviser is Dr. Kelvin Droegemeier, an expert in high-resolution numerical weather prediction from the University of Oklahoma.

And consider that the U.S. Congress knows about the problem and has passed two pieces of legislation, the Weather Research and Forecasting Innovation Act of 2017 and National Integrated Drought Information System Reauthorization Act of 2018, that highlights problems with U.S. weather prediction and provides some needed resources.   Another positive is that leaders of the NOAA Earth Systems Research Lab (ESRL), a group responsible for development of new U.S. models, are now committed to working closely with the NWS operational folks.  Five years ago this was not the case.

So we have extremely capable leadership in NOAA who want to fix the problem and a Congress who wants to help.  That is good--but it is not enough.

Now we come to the real problem, and why I am for the first time in years really optimistic. 


The key problem with U.S. operational numerical weather prediction has never been resources, it has always been about organization.  About too many groups, with too much resource, working on similar projects in an uncoordinated way.  Furthermore, the universities and the Federal government have rarely worked together effectively.

But this may all be changing.  NOAA leadership, with support from Congress, is about to set up an entity that will be the central development center of U.S. numerical weather prediction. 

This center is called EPIC (Environmental Prediction Innovation Center) and would combine the efforts of both NOAA and the universities (NCAR).   Done correctly, EPIC could lead to a much more effective and coordinated approach to developing a new U.S. global modeling capability.  A modular, unified national modeling system shared between government, academia, and the private sector.

Will the U.S. FINALLY organize itself properly to regain leadership in global numerical weather prediction?   Time will tell.  But I am more optimistic today than I have been in years.