Monday, July 15, 2019

A wet week during the driest time of the year

We are now entering the climatologically driest time of the year for our region, a period when it is not unusual to get no precipitation for weeks.

But not this year.  It is now raining in parts of our region and that is just a preamble to the rainy period in front of us. 

To put it a different way, more JAWS (July Abnormally Wet Systems) will be making landfall on our coast.

Just to give you some perspective, here is the annual climatology of precipitation at Sea Tac Airport--specifically, the probability of getting .01 inches in a day.  During the next few days it will drop to around 10% ..or even a bit lower.  July 29th is typically  the driest day of the year, so if you are planning an outdoor activity (like a wedding or barbecue), THAT is best day to do so. (I know this is short notice if you were planning to tie the knot)


But our golden end of July won't be so golden this  year.    Rain moved in this morning, mainly south of Seattle, as evident from the weather radar, and some of it is heavy.

Weather radar image at 7:30AM Monday

And this is just the start.  Let me show you the predicted 24-h precipitation total during the next week.

The 24-h ending ending 5 PM today (Monday)-- rain over the coast, with light stuff from Seattle south.


The next 24h (ending 5 PM Tuesday) shows light stuff over western WA, but more  more over Idaho and Alberta.


Now you need the JAWS music.  Below is the 24-h ending 5 PM Wednesday, showing moderate rain hitting BC and northwest Washington.   Nice wetting over the Olympics and north Cascades.


And on Thursday, the heavier stuff moved down the Cascades to Portland.


And even more rain over BC and NW Washington on Friday.


 Now you really want to be impressed?  Here is the total accumulation through 5 PM Saturday. British Columbia will be soggy with substantial rainfall in the mountains, and western WA, particularly in the mountains, will get enough to wet things down.  Puget Sound will be a bit rainshadowed by the Olympics.


The implications of all this?   The wildfire threat in British Columbia has been low and will remain low.   There is a good chance we will escape the BC smoke this summer, which was the main source of our smoke last year.  The clouds and rain will make our wildfire season shorter and of less intensity.  It will reduce our water use and help bring up our streams, particularly in areas in which they have been low (like the Olympic Peninsula).   With this precipitation, our July totals will much higher than normal for virtually the whole region.

The latest extended forecasts (e.g., the NOAA/NWS CFSv2) do NOT indicate an unusually dry August (see below).  The bottom line:  after all the scary talk about a dry summer with catastrophic wildfires, it is becoming clear that such an apocalyptic scenario is becoming highly unlikely and you can enjoy the sunny days ahead without worry or concern.



Saturday, July 13, 2019

My Forecast Discussion for Saturday, July 13: An Experiment

I wanted to try a new way to interact with all of you, doing a narrated description of the weather situation, with lots of weather graphics and loops.

Check the video below out, and let me know if you think this is something I should try again.  I am an amateur at this kind of presentation--so it can only get better....enjoy...cliff

Hit the play button to get it started....

Thursday, July 11, 2019

Sticky Air and Record-Breaking Moisture over Western Washington

How do I say this politely?

A number of people of been complaining to me about their discomfort the past few days and, yes, their profuse sweating.

The air has been humid and sticky.  Uncomfortable, even with relative modest temperatures.

The reason?  The air has been unusually moisture laden, particularly for the normally crisp, dry Pacific Northwest.

A good measure of the moisture content of air is the dew point temperature. The maximum amount of water vapor that a sample of air can "hold" depends on temperature.  Warmer air can hold more water vapor than cooler air. 

Imagine you start with some air with some water vapor in it, but the air is not saturated (the relative humidity is less than 100%).   If you cool that air down, you get to a temperature in which the air can just barely hold the moisture it started with and thus the air is saturated.  That is the dew point temperature.

The more water vapor in an air sample, the less you have to cool it to get saturation. Thus, moist air has a higher dew point than dry air.  To put it another way:  dew point temperature is a measure of the water vapor content of air.

Typically, the dew points in western Washington in July are in the 40s and low 50sF (see map below).    Why low dew points over the West Coast?  Because our air generally comes over the cool Pacific Ocean, whose low temperatures prevent the air from picking up a lot of moisture.  In contrast, over the SE U.S., the air comes off the very warm Gulf of Mexico and south Atlantic--so dew points are in the 60s to low 70s.  Miserable.


So here is the rule of thumb.  With dew point temperatures in the 40s and lower 50sF, you feel quite comfortable for normal summer temperatures.   You start to notice the moisture when the dew points get into the upper 50s and it gets "sticky" when the dew points rise into the lower 60s.  Mid-60s results in more sweating and by the upper 60s and lower 70s, the dew points are associated with real discomfort.  And wet clothing.

Now you are all dew point experts, it is time for the big reveal:  yesterday and parts of today, the dew points got into the mid and upper 60s in portions of western Washington.  

People noticed.  And many of you had glistening skin after the most minor of exertions.

To illustrate,  here are the dew points at 4 PM yesterday (Wed)--click on image to expand.  OMG!   69F at Tacoma's McChord AFB and low to mid-60s all over Puget Sound and southwest Washington.  No wonder we were all sweating.


And these high dew points were quite unusual.  Take a look of a plot of dew points at McChord over the past ten years.  The maximum dew point yesterday was a torrid 70F--the highest observed dew point  OVER THE ENTIRE PERIOD.

Or check out the surface dew point climatology at Quillayute, on the WA coast, which goes back to the late 60s.  Today's value at 5 AM (12Z, gray dot) was an all-time record for the date (the red line shows the records).


Why so humid yesterday?  A perfect set up.  We had an upper level trough moving moist air in from the southwest (see plot of water vapor in the air column--colors--and winds at 5000 ft).


And there was light rain, falling into the low-level air, that moistened the surface layer.  At low levels, we did not have much onshore flow at low levels, which would have brought in drier, cooler air from off the ocean.

So take a shower and get a cold drink. Or find a room with AC.  Thankfully, the dew points should slowly drop over the next day.


Tuesday, July 9, 2019

JAWS is Making Landfall on the Northwest Coast

Yes, JAWS. 

A July Abnormally Wet System (JAWS) is approaching the Northwest coast as I write this blog.  The view from space is scary and unusual for this time of the year.  It looks like a November satellite image.


And the Langley Hill radar this morning is picking up on the approaching rain bands .


The latest high-resolution UW WRF model forecast shows the rain coming into Puget Sound this evening--earlier on the coast and to the southwest. 
During the next few days, western Washington and Oregon should be wetted down, with potentially several inches in the high elevations of the Olympics, north Cascades, and mountains of southern BC (see below...total accumulation through 5 PM Friday).  The heaviest rain will be overnight tonight, but there will be plenty of showers tomorrow.


Remember the movie JAWS?  There were several sequels...and this situation will be no different.    JAWS2 will move in on Sunday--here is the 48 h total precipitation ending 5 AM Monday.  The NW part of the state gets  hit hard.


Why JAWS2?  Because another upper level trough will come through the region.


Unbelievably, the latest model runs promise JAWS3 between July 19 and 22. It will have even bigger (or wetter) teeth.

You may notice that the heaviest precipitation of all the JAWS storms is over western and NW Washington, exactly where the suggestions of local drought are being made (see latest drought monitor image).  Let's see whether they update this image.


It is clear now that this will be one of the wettest Julys in decades for our region, with a profound implication for NW wildfires and smoke.  Extended forecast models have been predicting this abnormally wet situation for at least a month--which is of great satisfaction to those of us working on longer term prediction.

Monday, July 8, 2019

Winter in July

A look at the latest enhanced infrared weather satellite imagery is a shocker, more reminiscent of mid-winter than mid-summer (see below). 

The image shows a huge weather system with plenty of clouds, rain, and wind over the eastern Pacific-- a system that is heading our way.    If this was a movie, appropriate music might sound like this.


In a normal year, our weather improves rapidly after July 5th.  But not this year.  In fact, it is quite possible than many Northwest locations (particularly over NW Washington) will have their wettest July in decades.

Precipitation will move in late Tuesday, and Wednesday should be wet.

Want to be impressed?  Here is the forecast accumulated precipitation forecast through 5 PM on Thursday.  Western Washington will be wet and southwest BC will be soaked.   Terrain areas will get as much as 1-2.5 inches (pink color).  You don't such amounts in July very often.


Looking more closely over Washington,  it appears that Seattle will be "relatively" dry, with .3 to .7 inches late Tuesday and Wednesday.  Even eastern Washington will get a piece of this.


All of this weather action is associated with an unusually strong upper level low off our coast (see upper level-500 hPa map for Tuesday at 5 PM.)  The low (red colors) will be accompanied by strong southwesterly flow  moving towards the Northwest.


And now the real shocker.  This is not the end of the unusually cool/wet weather.  The latest European Center model run suggests we will have more weather systems approaching the region during the next few weeks.

People are starting to complain about the cool/wet weather, but it is the price we pay for pushing off the threat of fires and smoke.

But what should we call this?  Januly? 

NO, I have a better idea:

JAWS:  July Atmospheric Weather System



Saturday, July 6, 2019

Fireworks and Air Quality

During the past year we have heard a great deal about the negative effects of wildfire smoke on human health, with even modest increases in small particles (PM2.5) resulting in breathing difficulties for folks with asthma, as well as generally increased mortality and morbidity.

With all this increased knowledge of the serious health effects of smoke, we need to take a serious look at the health impact of fireworks...both directly and as an initiator of wildfires.  Here is a plot of small particles in the air (PM2.5, sized of 2.5 microns or less) at Seattle.   You see the big spike?  That is July 4th.  About as bad as the particle loading during the wildfire situation last summer.

A blow-up of July 4th shows the rapid rise in the evening to a peak near midnight.
 I could show you the same thing for other major and minor cities around the region.

These surges in small particle pollution represent the direct effect of the fireworks. But it is worse than that.  A number of local wildfires have been caused by fireworks.   For example, a several hundred acre fire was started this week in Grant County (see below).
Screenshot courtesy of KOMO news.

And then there was the huge Eagle Creek Fire near the Columbia Gorge that burnt 50,000 acres over three months, defacing one of the most beautiful areas of our region.  Caused by a 15-year old kid with fireworks.


Here in the Puget Sound region alone, fireworks this year killed a 70 years old man, left a woman in critical condition, and caused dozens of serious injuries. Several homes were destroyed and dozens of people lost their homes.   The loud booms scare pets, make life miserable for thousands, and are acutely disturbing to our veterans with PTSD.

Quite honestly, it is time for a regional ban on personal fireworks and real enforcement by local police forces.   Here in Seattle, many of the parks were war zones (e.g., Mathews Beach, Carkeek, etc.).  And local police do little.  And don't forget the pollution from these devices (see below from Mathews Beach), both in terms of debris and the toxic chemical emissions.


It is time for a general ban in selling personal fireworks. 

Is it not strange, that local native American tribal groups, who speak eloquently about protecting the land and the environment, are in the business of selling these devices... including the largest and most explosive ones? Is it not equally strange that the Seattle Times, which has done many articles on important environmental issues, has a front page article praising the fireworks business?  And where  are our state's environmental leaders on this issue, such as Governor Inslee and Commissioner of Public Lands', Hilary Franz?   

There is a lot of talk about protecting our environment.   This is an area where something needs to be done.


Thursday, July 4, 2019

British Columbia is About to Be Inundated

If you are heading north to a vacation in British Columbia, you might turn around.  It is going to be extraordinarily wet up there. 

Bad for outdoor fun, very good for suppressing wildfires.

You won't believe what I am about to show you.   First, here is the predicted total precipitation through 5 PM Saturday.  Cross the international border and you will get drenched, with some locations getting 2-5 inches.    And this is supposedly the dry season.


Next 72 hours (ending 5 PM Tuesday)?  Much more precipitation in the same east-west band. 

Amazing.  The north Cascades gets a piece of it, as does the northern Rockies.   But look offshore!  An area of rain is heading inland from the southwest, with the Oregon coast starting to get wet.  Will that system hit Washington?


How about the next period?   Here is the 48 h total ending 5 AM Thursday.  Western Oregon and Washington get wet, with roughly an inch of rain.    This event, plus what we have gotten so far, will make this one of wettest Julys in recent memory in western Washington.


What about other forecast systems?  They show the same thing.  Here is the difference from normal (the anomaly) of precipitation for the next 10 days from the highly skillful European model ensemble. 

Major wet anomaly over southern BC, with above normal precipitation extending over western Washington.  Wetter than normal as well over northern Idaho and Montana.

The implication of all this for the summer wildfire and smoke season  in the Northwest is substantial.   The surface over much of the region is moist and will remain so.  There is no hint of developing strong, dry offshore (easterly flow).  Objective measures of fire threat suggest low probabilities (see below).

It is becoming increasingly clear that this will be a very benign July for wildfires and smoke and the forecast models are suggesting that this moist situation will continue into August.   Thus, it is a bit frustrating that certain media outlets and some public officials are still suggesting that there will be an unusually severe wildfire/smoke threat this summer.    And enjoy the fourth tonight...should be dry here in Washington.



Tuesday, July 2, 2019

Alaska Smoke Reaches Washington State (Aloft)

Although there are no major wildfires anywhere over the Pacific Northwest right now, there are many large fires burning over Alaska, producing lots of smoke.    Some of this smoke has extended southward over the Pacific Northwest.

Alaskan has been both warmer than normal during this spring and there are many wildfires burning over the  that state (see below)


For the past several days, some of the smoke has been swept southward, reaching British Columbia and even Washington State.   A measure of the smoke in the air, the aerosol optical thickness for 2 PM today is shown below...you can see what I mean


 High-resolution GOES-17 satellite pictures have clearly shown some of the smoke aloft (see image from Sunday below).


And the NASA MODIS Image from Saturday shows plenty of smoke over BC.



The smoke has remained aloft and air quality at the surface has remained excellent around the region  (see the values of small particles at Seattle below)


Regarding our very wet July 2, the precipitation will end tonight and expect improving conditions through July 4th.   Enjoy the holiday....and be mindful of the substantial smoke that will be ejected into the atmosphere that day.

Sunday, June 30, 2019

Freezing Temperatures and Puffy Cumulus Clouds

Before I discuss the impact of cold air aloft, let me show you a shot of the beautiful sunrise of Saturday morning for the Seattle PanoCam.   Love the reflection off Lake Union.


For the past several days, unusually cold air, associated with an upper level trough has been positioned over our region, resulting in cold nighttime temperatures east of the Cascades and puffy cumulus clouds over much of the region.  Below is a nice example from North Seattle Saturday morning.


An upper level chart (500 hPa, about 18,000 ft above sea level) for Friday morning shows the upper level trough (solid lines) and the cold temperatures (blue colors) over us.


With cold air aloft and relatively clear nighttime skies, some locations in western Oregon/Washington dropped into the mid-40s, while some locations in eastern Oregon plummeted to freezing Friday and Saturday morning (Saturday mornings lows shown below).



With cold air aloft and strong heating from the powerful near-solstice sun, there has been a large change in temperature with height (a large lapse rate).  This leads to instability--up and down motions in the lower atmosphere--as the atmosphere start to convect.    Such convection leads to the puffy white cumulus clouds, which form in the upward motion.   

The convection is enhanced over high terrain (which acts an elevated heat source).   A visible satellite image shows the cumulus clouds from space--you can see how high terrain is favored.


The troughing/low pressure aloft is weakening today, but should re-strengthen by Tuesday (see upper level map at 2 AM Tuesday)


As a result, precipitation is not over for us--with showers quite possible on Tuesday.  The accumulated precipitation through 5 AM July 4th, show substantial amounts over NE Washington and BC, with some extending down to Portland.


July 4th?   Looks dry over western Washington, with highs in the mid-70s.   Perfect for outdoor activity. 


Friday, June 28, 2019

A Quieter Than Average Wildfire Season So Far

With all the talk this spring of a severe and early wildfire season in the Northwest, the opposite appears to be occurring.  Currently, there are no major fires in Washington or British Columbia, with one small fire (140 acres) in Oregon.


Compare this situation to last year, when there were already a number of large fires in British Columbia.  As shown by the NOAA HRRR smoke model, the air is smoke-free over the Northwest (there are fires over the Southwest)




Looking more broadly, the Year to Date fire statistics for the entire U.S. (from the U.S. Interagency Fire Center) shows that there have been less fires and less acreage burned this year than any time in at least 10 years (see below).  But for the Northwest, it is even better than that, since most of the fires so far have been Alaska.



A key factor in this smoke free situation has been the normal weather conditions with precipitation and clouds that we have "enjoyed" much of the month.  Of particular note has been a persistent trough of low pressure over the region the last few weeks.  As a result, fuel moistures have been reasonable and the official North American fire danger map shows low danger over much of the Northwest, BC, and Alberta.


Proof of this benign situation has been the lack of fire starts after we got hit hard by lightning the last few days.  For example, here are the lightning strikes during the past two days from the national lightning network. Impressive for our region.




And the precipitation and clouds are not over.  Although we will have breaks with sunny skies and normal temperatures, the trough is going to hang around.  The European Center ensemble for precipitation through 5 AM Monday July 8th, shows plenty of precipitation in BC and northern WA. over the next 10 days.


At this point, it is becoming clear that there won't be a big early start to the fire season in BC.  Southern Oregon and N. CA have been wet, so fires will be delayed there.  I believe we can look forward to at least a month before significant fires and smoke will be in the picture.  Quite possibly longer.

And, as I have noted before, the long-term forecasts are favorable, with the International Subseasonal Ensemble (IMME)  and US CFSv2 models suggesting normal or wetter than normal conditions over the region (see below)


There has been quite a bit of hype and exaggeration about a very bad smoke season this year (from some unnamed politicians and media outlets).  Reality looks far better.  And even though things look favorable at this point, it is always good to prepare--like getting a top-of-the-line furnace filter, a N95 face mask, and the like.