Sunday, August 20, 2017

How Will the Eclipse Change U.S. Weather on August 21?

The total eclipse of the sun will profoundly change the amount of solar radiation reaching the surface on Monday, August 21st.

So how will this alter the weather across the nation?  Most of the usual weather prediction models  (such as the UW WRF) will not include the loss of solar energy in their forecasts.  But fortunately, my colleagues at NOAA ESRL have for the first time included the eclipse effects in a weather prediction this case the HRRR--the high resolution rapid refresh model.

To test the impacts, they ran the eclipse radiation code in a test run, using the weather situation of August 4.    Let me show you what they found--simulating for only the core hours of the event:  17, 18 and 19 UTC (9, 10, 11 AM PDT) on August 21st .

The radiation reaching the surface is shown below...the top line is using the normal (non-eclipse) radiation code.  The second line is with the case.  The bottom is the difference.  You can see a round region of profoundly reduced global radiation moving eastward across the nation over two hours.

But what about temperature?   Major cooling, with some areas cooled as much as 6°C (11°F)...but not over the Northwest, where the signal is about half as strong.   One major reason is that the eclipse hits earlier on the West Coast, when solar radiation is weaker, compared to the mid-day eclipse to the east.
What about wind?  Yes, there are effects, including effects on wind energy.  Here is the change of wind speed at 80m....near hub height of many wind turbines.  Interestingly, the wind speed effect is delayed a bit, with roughly a 1 meter per second (around 2-3 mph) reduction over the western U.S.
There have been a number of eclipse-weather studies, with documenting temperature declines at much as 15F--although in the Northwest I expect more like 3-6F in the region of totality.   So if you can, try taking temperature reading during the event and let us know what you find.

Eclipse Forecast Update

Everything looks good for the region of totality.  Best conditions around Salem (no clouds or smoke), with clear skies, with some smoke to the east.  Here is the cloud forecast for 10 AM. Great for Oregon.  Some residual clouds around the Sound.  Clouds along the coast.

Friday, August 18, 2017

Eclipse Weather Update: Will the Partial Eclipse Be Visible in Seattle? What will happen in Oregon?

Many of you are in the final planning stages for the big solar eclipse.    So lets update the situation and discuss some of the nuances and details that I left out in previous blogs.

The basic story is still the same.  Partial cloudiness around Seattle, lots of clouds along the Pacific coast.   Good viewing in the Willamette Valley eastward, with the threat of smoke in parts of eastern Oregon.

First, the wildfire/smoke issue. There are several fires burning in the Oregon Cascades and some of the smoke is being blown to the east and south.  Fortunately, most of the smoke is avoiding much of the totality region in northeast Oregon.  The Willamette Valley is clear.  Smoke is probably not a major issue until you are near or immediately downstream of the fires.

Next, lets turn to the low cloud forecast of the latest high-resolution (4km grid spacing) UW WRF model run.  The resolution is important, since we need to get the blocking effects of the coastal mountains correct.

At 8 AM PDT, lots of clouds over the coast and some marine clouds over Puget Sound.

 By 9 AM, Oregon is clear (except for the coast) and the low clouds are retreating around Puget Sound (still near the water).
 By 10 AM (right before the greatest lunar coverage of the sun), Puget Sound is clear, but the Strait and the coast are covered.

 No here is a major issue.  The UW WRF model does not have the reduction of solar radiation by the eclipse, which will start to become significant around 9 AM.  So the clouds may burn off more slowly than forecast after 9 AM.

Thus, the Puget Sound region  is on the edge.  There could be some low clouds, particularly near the water, at eclipse time.   My advice is you want to see the eclipse and clouds are there around 8 AM...head east or up in elevation.  Even Bellevue and Issaquah would be much better.

Still looks good in the Willamette Valley based on the UW WRF model.

How about the European Center model?  Here is the forecast for 11 AM (don't have it every hour).  Oregon looks fine, although there is some high clouds (cirrus) around Portland.  An irritant, but you would still seen the show.   The coast is cloudy like UW WRF.  Puget Sound looks clear, but clouds in the Strait. Thicker high clouds over eastern WA.

How about the official National Weather Service forecast for cloud cover at 11 AM?  Good in the Willamette Valley (4% coverage), 0-2% coverage in eastern Oregon, bad on the coast, but good (7%) in Puget Sound.

As we get closer to the event, another modeling system will be available (the NWS HRRR), which DOES include the reduced strength of the sun in its prediction.   I will be watching it carefully and let you know.

So the bottom line is still pretty much the same.  The coast will not be the best place...if you are there, head a few miles east and upwards into the coastal mountains.  Salem and vicinity should be great, with no smoke.  Eastern Oregon will be clear, with smoke in places.   Seattle is on the edge, but probably will have decent sky opening away from Sound.

Enjoy.   I received about 20 emails today from folks looking for eclipse glasses...sorry, I don't know if any local stores have stock....many are sold out.

Thursday, August 17, 2017

The Best Place to View the Total Eclipse in the U.S.: Salem, Oregon and Vicinity

We are now close enough to the eclipse to have great confidence in the weather forecasts and the expectations regarding wildfire smoke.  Computer models are in substantial agreement and forecast uncertainty is far less than a few days ago.

The conclusions one draws from the predictions are clear:

Salem, Oregon and the adjacent areas in the Willamette Valley of Oregon will offer the best viewing in the entire nation..  

Clear skies and smoke-free air, resulting in exceptional viewing conditions.   And it has the added benefit of being near a major interstate (I5) and several large roads (99E, 99W).

Let me show you why western Oregon's Willamette Valley offers such good viewing.  Let us begin by reviewing the path of totality over the U.S.--a  curving path stretching from northern Oregon to south Carolina.

Here is the total cloud forecast from the European Center model, one valid at 11 AM PDT on Monday, August 21st.  A red line shows the path of totality.  Lots of clouds in Great Plains and mixed clouds in the southeast.  Only the section over Oregon is completely clear.

A blow-up of the cloud situation in Oregon shows the predicted cloud-free conditions for northern Oregon.   Only the coastal zone is potentially problematic, with some low stratus clouds.

What about visibility?  Moist air can result in enhanced particle sizes and precipitation is clearly bad for eclipse viewing.    

Here is the visibility forecast for the U.S. at the same time from the ECMWF model (which does NOT include smoke).  Degraded visibility in the southeast U.S. and central U.S.  The best visibility (white color) in the Willamette Valley and SW Oregon (see blow up map for more detail)

Finally, there is wildfire smoke and unfortunately, there are a lot of fires going on right now over the western U.S. and plenty of smoke.   For those viewing on the eastern slopes of the Oregon Cascades and in eastern Oregon, a veil of smoke will be present and will undermine clarity to some degree.   As shown below, there are a number of fires burning over Oregon and particularly in the areas of totality (north of Bend):

The current satellite observations of smoke impacts (actually atmospheric optical depth) indicates smoke over the Northwest, particularly eastern Oregon (see blow up below).  But if you look carefully, once sees that the Willamette Valley is virtually smoke free.

The Canadian Smoke model's 48h forecast for Friday at 5 PM PDT is showing plenty of smoke eastern Oregon, but not on the west side.  Lots of smoke over the eclipse path of eastern Wyoming and Nebraska.

I could you show you other models, but the answers are the same:  The northern Willamette Valley around Salem will offer the best and most reliable viewing of the 21 August total eclipse of anywhere in the nation.  

You don't like models and want to get the predictions of my colleagues at the National Weather Service.   Here is their prediction for % cloud cover at 11 AM on Monday.  By far, the lowest percentage (5%) is in the Willamette Valley.

A blow-up map confirms this.  Salem is 5%.

 So if you are in Seattle, Portland, and California, western Oregon should be wonderful to get an optimal view of the total eclipse.

The big question, of course, is traffic.    I suspect the big traffic issue won't be before the event (since folks will getting into position over several days).  It is after the eclipse is over.  Everyone can't leave at once.  And governmental entities need to set up some major viewing locations (with bathrooms) and facilitate access to I5 and other major roads.

Tuesday, August 15, 2017

Eclipse Weather Forecast: Looks Good for BOTH Sides of the Cascades

I didn't want to make this forecast until there was some real skill to the forecast.  Today, 6 days from the big event, I believe I can provide actionable information, although I would not pretend there are no uncertainties.  

The bottom line:  it looks good over BOTH sides of the Cascades, except for the immediate coast.

Typically, there is little skill for weather forecasts greater than 10 days, marginal skill for 7-9 days, and rapidly increasing skill for weather predictions of less than a week.  

Furthermore, we have tools, and particularly ensemble forecasts (where we run our models many times), that can quantify the forecast uncertainties and tell us when we have periods of greater or lesser predictability.  

Back to the eclipse forecast.   As most of you know, the area of totality will run across northern and Oregon, roughly on an east-west track (see map).  Totality, which can last up to around 2 minutes, begins around 10:15 AM PDT Monday August 21st along the coast and 10:25 AM at Oregon's eastern border.  10:15 AM PDT is 17:15 UTC or universal time.  Keep that in mind for later.  Seattle will have a partial eclipse (about 92% coverage by the moon), with the darkest time around 10:20 AM PDT.

The big question for eclipse watchers in Washington and Oregon is whether they should be on the east or west side of the Cascades (or in the mountains!).  There are, in fact, three major threats for watching the eclipse:

  1. Low marine clouds along the coast and potentially the Willamette Valley
  2. Smoke from wildfires
  3. A major frontal system with deep clouds (like over the past weekend)

First, lets consider wildfire smoke.  Last week, there was dense smoke over the region, much of it from the big fires in British Columbia, with an assist from local fires on the eastern side of the Cascades.  With a shift to a very different large scale weather regime, the BC smoke is now heading more to the east, leaving Oregon and Washington in the clear.  Currently (Tuesday AM) air monitors show little smoke at ground level over most of the area.

And the 48 hour forecast of the Canadian smoke model (FireWork) show little smoke and the BC smoke is heading away from us.  I expect that to continue for the rest of the week based on current model forecasts.

There are some local fires burning in our region (see current fires below), but most are small or contained, and the amount of regional smoke is relatively small away from the fires (although there is a thin veil from them).  So away from their immediate vicinity, one should not expect a major impact.

 The weather should be typical this week, with no lightning over the central and northern Oregon one should not expect new wildfire initiation.    Furthermore,  the eclipse is close enough to solar noon that the sun will be relatively high in the sky, and thus the sun's light will not be going through a large amount of atmosphere, as occurs near sunrise and sunset.

Bottom line:  smoke is not going to be a major issue for this eclipse unless you are immediately downwind of a local fire.

But what about clouds? 

 Here is the latest UW WRF forecast for cloud water valid at 11 AM Monday morning.  We see a lot of low marine clouds over the Pacific, but they don't extend past the coastal mountains.  Salem and the Willamette Valley would be in the clear, as would those in Washington State and eastern Oregon.  Praise to the weather gods.

What about the European Center global model, the world's best?

Here is its forecast for 11 AM for total clouds and low-middle-high clouds.   No low and middle level clouds over the eclipse zone...which is very important.  There are some high clouds over Washington and NW Oregon, but these would be thin cirrus.  An irritant, but it probably would not ruin the show. And keep in mind that the position of these high clouds is very uncertain.

As I have discussed a hundred times in this blog, state-of-the-art forecasting does not look at one forecast, but rather uses ensembles of many forecasts to judge uncertainties and to provide probabilistic predictions.   So let us look at ensembles for this event.

First, take a look at the large, 51-member European Center ensemble prediction for total clouds at Salem, Oregon. The 51 rows are from the 51 members of the ensemble, and time is in UTC (0000 UTC 21 August is 5 PM 20 August PDT).  The situation around 1800 UTC 21 August is a mixed bag, but most members have little or no clouds--roughly a 25% chance of (high cirrus) clouds.

What about Redmond, Oregon on the other side of the Cascades?  Slightly better (20% chance of some high clouds).  But there is the threat of a thin veil of smoke there.

Along the coast at Newport, Oregon?   Around 40% chance of clouds.

Checking out an independent, large ensemble systems (the US-Canadian NAEFS) for Portland (closest available), suggests a high probability of very little clouds, with only a few members indicating 10-20% coverage (bottom row).

I could show you much more, but you get the message.   The best weather technology we have suggests a favorable situation for viewing the total eclipse in the Willamette Valley and in eastern Oregon. 

 Here in Seattle there may be some thin high clouds, but you should still enjoy the partial eclipse.
The place that is iffy is along the Oregon coast.  If you are there, a short trip into the coastal mountains of Oregon should do the trick (assuming the roads are not grid locked).

I believe that model solutions are relatively stable now--but by Friday we should be very confident in Monday's forecast.  Enjoy the eclipse and make sure you are careful not to look directly at the sun.

Sunday, August 13, 2017

Wildfire Smoke Brought Radioactivity and Ozone

Now many folks were unhappy with the low visibility and dismal skies during our wildfire smoke period.  And I know a number of you were discomforted by the particles in the air.

But there is more.   According to U.S. government measurements, radioactivity and ozone were higher as well.

I wasn't aware of the radioactivity issue until I received an email from Tim Celeski of who provided a link to the Environmental Protection Agency's RadNet website (another good reason why we need EPA, by the way).

Here is the gamma radiation count from Seattle. Gamma radiation is very high energy electromagnetic radiation and are capable of ionizing (stripping electrons) from atoms.  Values jumped up on August 3, when the smoke reached Seattle and started to decline yesterday.  Note that is a logarithmic scale so the jump is significant.

 They also break the radiation down by energy range.  Similar story.

Wildfires inject burned and other materials into the air, and if any long-lived radioactive materials (like Cesium-137) attach to the smoke particles, they can travel substantial distances.  As noted by two colleagues of mine at WSU (Brian Lamb and Yunha Lee), such suspension of radioactive material by wildfires has been observed and studied before.

So where did the radioactivity come from in the soils and plant materials in the area of the BC fires?  I am no expert in this, but one could speculate there could be deposition from the Fukushima event, the remnants of previous above ground atomic testing, or perhaps natural radioactivity in the soils.   Perhaps one of you knows more about this.

And then there was ozone...VERY high levels of ozone that were produced by the numerous BC fires.  

Fires produce nitrogen oxides and hydrocarbons that can combine to produce ozone. . According to my UW Bothell colleague (and a specialist in NW atmospheric chemistry)  Dan Jaffe, the ozone levels were stunning.

8hr average values at Enumclaw hit 103 and sites near PDX reached 116.   And many sites that don't usually exceed the standard, like Eugene, were way over.

This chart shows maximum 8-hr ozone averages on August 3.  Reds are very high.

The U.S. ozone standard is based on a maximum amount of 70 parts per billion (ppb).  Specifically, an area will meet the standards if the 4th highest maximum daily 8-hour ozone concentration each year, averaged over three years, is 70 ppb or below. Ozone can irritate the lungs and sensitive nasal passages.

In total, Enumclaw has been over the 70 ppb standard  for 8hr on 8 days since 7/31. Wow.

How about Mud Mountain Dam (near Mt. Rainier) and Issaquah (see below)?  Lots of times above 70 ppb!

According to Dr. Jaffe, we have not seen O3 like this in decades.

So with smoke adding lots of particles into the atmosphere (documented in previous blogs), high ozone levels, a depressing sky with little visibility, and some radioactivity thrown in for good measure, it is no wonder some folks were not feeling so good during the last week.

Friday, August 11, 2017

The End of Smoke, the First Rain, and Cooler Temperatures Return: But Are There Dangers with this Change?

We are about to experience a major shift in our weather, one that will end the above-normal temperatures, bring the first real rain of summer, and push the smoke away from western Washington.  Normal conditions will return.

But as we will see, there are some dangers to this change, including pole fires, power outages, more wildfires, and slippery roads.

During the past week, a ridge of high pressure has dominated the flow over our region, as shown by this upper level chart for Tuesday at 5 PM.  It has been a very stable pattern, resulting in warm conditions and light winds.  The smoke settled in over our region.

But the models are emphatic that the ridge will move inland, and a Pacific trough will approch us.  The forecast map for Saturday at 5 PM shows you what I mean.

Today (Friday) will be the last warm day before the change, with temperatures rising into the lower 80s.

But Saturday will be a different story, with increasing clouds and wind from the approaching disturbance.  The smoke will be pushed eastward.  And even some light showers are possible.    The major rain will wait until Saturday night and Sunday morning.

Here are the 24-h total precipitation forecasts for next few days.  For the 24 h ending 5 PM Saturday, light showers over western WA and what looks like some convective (thunderstorm) precipitation over eastern Oregon.  It is good the eclipse is not tomorrow!

But the next 24 hr (ending 5 PM Sunday) is much wetter over western WA and the coast.  No much by winter standards,  but the most we have seen for months (roughly .1 inches over the interior and .5 inches along the coast)

Now what are the potential downsides to this change of weather?

1.  Slippery roads.  The first rain of the late summer falls on roads that have accumulated oil, dust, and other particles, often producing a transient slippery surface.  So drive carefully when the rain starts.

2.  Pole fires and power outages.   According to a retired City Light employee I have worked with, the dust and muck deposited on wooden power poles can become conductive with a little rain, causing short-circuits, fires, and power outages.  The long period without rain this summer makes us particularly vulnerable.

3.  Lightning.   The approaching trough can initiate thunderstorms that could start new wildfires over the Cascades and eastern WA/Oregon.  And yes, perhaps endangering a few golfers.

I suspect most of you will be happy with the return of normal weather.  

Many are starting to think about the eclipse.   Well, the latest upper level (500 hPa)  forecast from the National Weather Service GFS model for 11 AM Monday morning (21 August) shows a trough, with clouds and showers, over the region...not good!   But don't worry.... the skill at 10-11 days is very poor.

Thursday, August 10, 2017

The Ultimate Wildfire Smoke Video for Puget Sound

Greg Johnson of Skunk Bay Weather has produced a marvelous video from his site on the northern Kitsap Peninsula showing the changing effects of the wildfire smoke during the last week.

What he did was to combine video of the sunrises from late July until today, with the first showing clean air conditions, and the latter ones reflecting the effects of the smoke.   It is just stunning.   Click on the link to check it out.

And now the good news. Friday will be the last day of above normal temperatures for a while. Over the weekend the large scale flow pattern will shift, with much cooler air moving in.

Rain will return.

The smoke will be blown away from Puget Sound.

Clouds will again grace our skies.

And some folks will stop claiming the smoke is a sign of global warming.


Eclipse forecasts.   It is too earlier to do so skillfully, so my first analysis of the eclipse weather will be on Monday.

Wednesday, August 9, 2017

Believe it or Not! Wildfire Smoke Is Cooling the Northwest

Today was another warm day, with Sea-Tac hitting 91F and temperatures rising above 100F in the Columbia Basin of eastern WA (see map).

But do you know that our temperatures this week would have been much warmer this week if it weren't for the substantial smoke covering our region?  Smoke that predominantly came from British Columbia?  Believe it or not, the proof is at hand!

The plume of smoke above us has reduced the amount of solar radiation reaching the surface...thus producing less surface warming.

Why is that true?  Because the smoke particles both scatter some of the solar radiation back to space and absorbs some of the sun's rays, the latter causing the air higher up in the atmosphere to warm.  By either mechanism, less solar radiation reaches the surface.

  Here at the University of Washington, the amount of solar radiation reaching the sensors at the top of our building has been substantially reduced by the smoke:  the numbers are shown below, dropping from 25.37 on August 1 to around 19.15 MegaJoules per meter squared on August 5-6.  Roughly a 25% drop in solar radiation!

Radiation in MJoules per m2
7/31   26.80
8/1     25.37
8/2     23.22
8/3     22.55
8/4     23.33
8/5     19.19
8/6     19.14
8/7     21.09
9/8     22.62

OK, the amount of solar radiation is less, but how can we prove that it cooled us off? 

To explore this issue, I asked Jeff Baars, a research meteorologist in my department, to explore the smoke's impact by taking difference between the UW WRF model forecast for surface (2-meter) air temperature and observations.  The UW WRF model does not include the effects of smoke (we are working on it!), so the difference between our model forecast and reality should reveal the effects of smoke.   The expectation is that the model without smoke will be too warm...but by how much?

Here is the difference between the forecast (72h) and observed temperatures at Seattle-Tacoma Airport from 23 July through last night, for the forecasts valid at 5 PM each day.  The various colors are for different resolution UW WRF forecasts (36, 12, 4, and 1.3 km grid spacing).  Before the smoke reached our region the WRF model forecasts were quite good, with very small errors.  But after the smoke hit, the errors reached around 10F, with the model being too warm.   Implication:  the smoke cooled Sea-Tac by 10F on two days, and less amounts on others!

What about Bellingham, a location even closer to the smoke source in BC?    Wow... the cooling effect of the smoke reached 12-14F!

Portand?  The smoke took a bit longer to get down there, but when it did, the temperature effects were substantial (see graphic).  The model seems to be 2-3F too warm before the smoke hit, but when it did (August 7-8), the cooling effect was large (over 10F).

We did a similar analysis for 5 AM, when temperatures are near their daily low, and found little effect.  This is not unexpected:  much of the smoke is higher up, where the air is cooler and the smoke particles are relatively small compared to the wavelength of infrared radiation, which is the key player at night.

The smoke was substantial today and even worse this evening, something shown by the small particle concentration (PM2.5) at Seattle and Tacoma (see below from Puget Sound Clean Air Agency). Levels of 60-90 micrograms per cubic meter are unhealthy of vulnerable populations.   Weakened solar radiation coupled with cooler temperatures also means that there is less drying of the soil.

According to the Canadian smoke forecast modeling system, we have several more days of this.  And meteorologists need to get the effects of smoke into our weather forecast models, something that is generally missing.

So should we thanks the Canadians for keeping us cool, or curse them for smoking us out?  I will leave that for you to decide.


Announcement:  Atmospheric Sciences 101

I will be teaching Atmospheric Sciences 101 this fall if anyone is interested either as a UW student or the Access Program for those over 60.  This is a general intro to weather and weather prediction.  MTWTh 10:30-11:20, Kane Hall.  No remote access...sorry.