Fogs Engulfs Seattle

There was a stunning series of images this morning from the Space Needle panocam as inland fog pushed over Seattle.

It was clear this morning around sunrise over downtown Seattle, but a shallow fog bank loomed to the southeast (picture below for 7:30 AM).

By 8:30 AM the fog had begun to move across downtown.

And  by 10 AM the city was well covered, with only the top of the Columbia Center extending above the cloud deck.

At 11:30 AM,  the fog had begun to thin (see below)

But looking towards Queen Anne hill, one could see a wonderful example of a dramatic optical effect--a glory- centered at the top of the shadow of the Space Needle.  Note the circular array of colors caused by dispersion effects of diffraction.  Magnificent.

The fog bank also moved in at the NOAA facility near Magnuson Park in NE Seattle and the vertical sounder there showed how the temperature structure was altered by the fog bank (see plot below of temperature with height a various times).  At 1200 and 1300 UTC (4 and 5 AM PST), temperatures warmed with height in the lowest 100 meters (cyan and yellow lines).  But after the fog moved in (black, red and green lines), there was a large cool down in the lowest 300 meters (about 600 ft).   Not much change above that. 

Finally, the fog was evident in the 10:45 AM image from the new GOES-17 weather satellite (see below).  Fog extended east, north and south along the river valleys, but ended at the Sound.  A wonderful morning to hike up to the top of Cougar or Tiger Mountains and look down on the clouds below.  Great visibility aloft.  And the fog won't last...much will burn off during the next few hours.

from Cliff Mass Weather and Climate Blog http://bit.ly/2RsVTPC

Fogs Engulfs Seattle

There was a stunning series of images this morning from the Space Needle panocam as inland fog pushed over Seattle.

It was clear this morning around sunrise over downtown Seattle, but a shallow fog bank loomed to the southeast (picture below for 7:30 AM).

By 8:30 AM the fog had begun to move across downtown.

And  by 10 AM the city was well covered, with only the top of the Columbia Center extending above the cloud deck.

At 11:30 AM,  the fog had begun to thin (see below)

But looking towards Queen Anne hill, one could see a wonderful example of a dramatic optical effect--a glory- centered at the top of the shadow of the Space Needle.  Note the circular array of colors caused by dispersion effects of diffraction.  Magnificent.

The fog bank also moved in at the NOAA facility near Magnuson Park in NE Seattle and the vertical sounder there showed how the temperature structure was altered by the fog bank (see plot below of temperature with height a various times).  At 1200 and 1300 UTC (4 and 5 AM PST), temperatures warmed with height in the lowest 100 meters (cyan and yellow lines).  But after the fog moved in (black, red and green lines), there was a large cool down in the lowest 300 meters (about 600 ft).   Not much change above that. 

Finally, the fog was evident in the 10:45 AM image from the new GOES-17 weather satellite (see below).  Fog extended east, north and south along the river valleys, but ended at the Sound.  A wonderful morning to hike up to the top of Cougar or Tiger Mountains and look down on the clouds below.  Great visibility aloft.  And the fog won't last...much will burn off during the next few hours.

from Cliff Mass Weather and Climate Blog http://bit.ly/2RsVTPC

Year in Review

With new year's coming up tomorrow night, it is appropriate to look back on the weather of the past year.

The essential take away:  2018, and particularly the late spring and summer, were much warmer than normal.

We can illustrate this with a nice graph (see below) produced by the National Weather Service for Seattle-Tacoma Airport, showing the observed temperatures (blue line), the normal range (green shading) and the records for each date (high records-red color, low records, blue color).

One is struck immediate by the many dates that were above normal, particularly from May 1 to Sept. 1).    A number of these days hit highs 10-15F above normal.    On the other hand, the annual extremes were not impressive...on day got to 94F and the lowest temperature all year was 24F, with only one cold spell in late February.

Precipitation was a very different story--the annual precipitation will end up slightly below normal (see middle graph, top of light green shows accumulated precipitation), resulting from a wetter than normal first half of the year, a dry summer, and moist late fall.

Snow in Seattle was almost absent:  about 1 inches compared to a normal total of around 6 inches.

A regional view of the differences from normal of temperature and precipitation for 2018 is shown below.   For temperature, the entire region west of the Rocky Mountains has been warmer than normal, particularly the U.S. Southwest.   Here in WA state, roughly 1-2F above normal.   But note the cooler than normal weather over the northern Plains.  That will be important.

Precipitation is more complex.  Most of the west was near normal in 2018, except from southwest WA to northern CA, where is has been quite dry.  The contrast across western WA is really substantial.

So what it the cause of the warm anomaly in the West?

Anthropogenic global warming might be making some contribution, but there is much more going on.    A hint at this comes from taking a broader perspective, looking at all of North America (see below).   This figure shows the temperature anomaly (difference from normal) for 2019.  Blue indicates colder than normal and  red/orange above normal.   The western U.S. is warm, but the middle of the country is cold, while the East Coast is warm.

This pattern was associated with an amplified upper-level wave pattern, with ridging (high pressure) over the West Coast, with troughing (lower pressure) over the central U.S..   This pattern was evident for much of the year, including our warm/dry period in November and during the late spring. 

To illustrate, here is a map produced by the National Weather Service showing the average upper level (500 hpa) height anomaly in November (sorry it is blurry, the government shut-down makes it impossible for me to get better graphics).  Red indicates higher than normal heights (ridging), blue indicates troughing).  Ridging produces localized warm surface temperatures, the opposite for troughing.  Ridging also suppresses precipitation, explaining our drier than normal conditions.

There is no reason to expect that this pattern has anything to do with global warming (note:  the "lazy jet stream" hypothesis has been firmly disproved in the peer review literature). 

How much of our warm year might be due to anthropogenic global warming?   We can get some insights into this by using the wonderful Washington State Climatologist climate plotting site (with kudos to Karen Bumbaco and Nick Bond).    The annual temperature in Seattle is shown below.  A small upward trend of perhaps .5F, with human caused global warming undoubtedly contributing during the past 30 years.  Other local stations are similar.

The take away is that most of the warming this year (1-2F)  is due to the anomalous upper level pattern, which is probably the result of natural variability.  Why am I stressing this point?  Because too many people, and unfortunately some in the media, make the assumption that every warm anomaly is mainly the result of increasing CO2 in the atmosphere.   This is simply not true.



from Cliff Mass Weather and Climate Blog http://bit.ly/2Sr4Oi0

Year in Review

With new year's coming up tomorrow night, it is appropriate to look back on the weather of the past year.

The essential take away:  2018, and particularly the late spring and summer, were much warmer than normal.

We can illustrate this with a nice graph (see below) produced by the National Weather Service for Seattle-Tacoma Airport, showing the observed temperatures (blue line), the normal range (green shading) and the records for each date (high records-red color, low records, blue color).

One is struck immediate by the many dates that were above normal, particularly from May 1 to Sept. 1).    A number of these days hit highs 10-15F above normal.    On the other hand, the annual extremes were not impressive...on day got to 94F and the lowest temperature all year was 24F, with only one cold spell in late February.

Precipitation was a very different story--the annual precipitation will end up slightly below normal (see middle graph, top of light green shows accumulated precipitation), resulting from a wetter than normal first half of the year, a dry summer, and moist late fall.

Snow in Seattle was almost absent:  about 1 inches compared to a normal total of around 6 inches.

A regional view of the differences from normal of temperature and precipitation for 2018 is shown below.   For temperature, the entire region west of the Rocky Mountains has been warmer than normal, particularly the U.S. Southwest.   Here in WA state, roughly 1-2F above normal.   But note the cooler than normal weather over the northern Plains.  That will be important.

Precipitation is more complex.  Most of the west was near normal in 2018, except from southwest WA to northern CA, where is has been quite dry.  The contrast across western WA is really substantial.

So what it the cause of the warm anomaly in the West?

Anthropogenic global warming might be making some contribution, but there is much more going on.    A hint at this comes from taking a broader perspective, looking at all of North America (see below).   This figure shows the temperature anomaly (difference from normal) for 2019.  Blue indicates colder than normal and  red/orange above normal.   The western U.S. is warm, but the middle of the country is cold, while the East Coast is warm.

This pattern was associated with an amplified upper-level wave pattern, with ridging (high pressure) over the West Coast, with troughing (lower pressure) over the central U.S..   This pattern was evident for much of the year, including our warm/dry period in November and during the late spring. 

To illustrate, here is a map produced by the National Weather Service showing the average upper level (500 hpa) height anomaly in November (sorry it is blurry, the government shut-down makes it impossible for me to get better graphics).  Red indicates higher than normal heights (ridging), blue indicates troughing).  Ridging produces localized warm surface temperatures, the opposite for troughing.  Ridging also suppresses precipitation, explaining our drier than normal conditions.

There is no reason to expect that this pattern has anything to do with global warming (note:  the "lazy jet stream" hypothesis has been firmly disproved in the peer review literature). 

How much of our warm year might be due to anthropogenic global warming?   We can get some insights into this by using the wonderful Washington State Climatologist climate plotting site (with kudos to Karen Bumbaco and Nick Bond).    The annual temperature in Seattle is shown below.  A small upward trend of perhaps .5F, with human caused global warming undoubtedly contributing during the past 30 years.  Other local stations are similar.

The take away is that most of the warming this year (1-2F)  is due to the anomalous upper level pattern, which is probably the result of natural variability.  Why am I stressing this point?  Because too many people, and unfortunately some in the media, make the assumption that every warm anomaly is mainly the result of increasing CO2 in the atmosphere.   This is simply not true.



from Cliff Mass Weather and Climate Blog http://bit.ly/2Sr4Oi0

Another Windstorm Tomorrow

This is almost getting routine.   Another wind event will occur tomorrow (Saturday), but with a bit of a different meteorological twist:  no major cyclone, but a warm front passage, followed by a strong cold front.

Today, I will show you some advanced meteorological technology for wind prediction, something developed at the UW with funding from Seattle City Light and the Northwest Modeling Consortium.   
This figure shows the peak wind gust forecast over the city of Seattle predicted by the National Weather Service (green line), a super-high resolution numerical model prediction  run at the UW(red line), and a collection of high-resolution forecasts (gray lines and blue line).    Showing many forecasts (or an ensemble), each slightly different in their initialization, provides a way of estimating the uncertainly in the prediction. All these predictions were started at 4 PM Thursday.

These forecasts are the gusts (short-term wind maxima), based on a calibration from historical periods.  Virtually all the models are going for a significant wind event on Saturday, with maximum gusts over Seattle getting to 40-50 mph (most places in Seattle will experience less) between 10 AM and 4 PM.    Note how the wind continuously ramp up starting this afternoon....this is associated with a warm front passage.

The latest high-resolution (1.3 km grid spacing) run is in (below).   At 1 PM Saturday, it is windy around central Puget Sound (gusts of 35-40 knots), and if you look carefully you will notice the windshift on the NW coast associated with the cold front.

 Three hours later, the cold front has reached Hoquiam, on the central WA coast, and and strong westerly winds have pushed into the Strait of Juan de Fuca.

Considering all the stress put on trees during the past two windstorms, I would expect for less damage this time, but I am sure there will be some power outages.

To give you a better view of what is going on, here is a plot of sea level pressure (solid lines), low level temperature (colors--yellow is warm, blue is cold) and surface winds.  The situation at 4 AM this morning, shows cold air over the interior and the warm front offshore (transition from green to yellow, and significant wind shift).

 By 10 AM Saturday, warmer air had spread over Washington and Oregon, leaving us in the warm sector.    Note the large north-south pressure difference--that is what will produce strong winds.

The winds should weaken Saturday evening, with cooler and partly cloudy conditions on Sunday.

New Year's Eve should be dry!

from Cliff Mass Weather and Climate Blog http://bit.ly/2RkKWzF

Another Windstorm Tomorrow

This is almost getting routine.   Another wind event will occur tomorrow (Saturday), but with a bit of a different meteorological twist:  no major cyclone, but a warm front passage, followed by a strong cold front.

Today, I will show you some advanced meteorological technology for wind prediction, something developed at the UW with funding from Seattle City Light and the Northwest Modeling Consortium.   
This figure shows the peak wind gust forecast over the city of Seattle predicted by the National Weather Service (green line), a super-high resolution numerical model prediction  run at the UW(red line), and a collection of high-resolution forecasts (gray lines and blue line).    Showing many forecasts (or an ensemble), each slightly different in their initialization, provides a way of estimating the uncertainly in the prediction. All these predictions were started at 4 PM Thursday.

These forecasts are the gusts (short-term wind maxima), based on a calibration from historical periods.  Virtually all the models are going for a significant wind event on Saturday, with maximum gusts over Seattle getting to 40-50 mph (most places in Seattle will experience less) between 10 AM and 4 PM.    Note how the wind continuously ramp up starting this afternoon....this is associated with a warm front passage.

The latest high-resolution (1.3 km grid spacing) run is in (below).   At 1 PM Saturday, it is windy around central Puget Sound (gusts of 35-40 knots), and if you look carefully you will notice the windshift on the NW coast associated with the cold front.

 Three hours later, the cold front has reached Hoquiam, on the central WA coast, and and strong westerly winds have pushed into the Strait of Juan de Fuca.

Considering all the stress put on trees during the past two windstorms, I would expect for less damage this time, but I am sure there will be some power outages.

To give you a better view of what is going on, here is a plot of sea level pressure (solid lines), low level temperature (colors--yellow is warm, blue is cold) and surface winds.  The situation at 4 AM this morning, shows cold air over the interior and the warm front offshore (transition from green to yellow, and significant wind shift).

 By 10 AM Saturday, warmer air had spread over Washington and Oregon, leaving us in the warm sector.    Note the large north-south pressure difference--that is what will produce strong winds.

The winds should weaken Saturday evening, with cooler and partly cloudy conditions on Sunday.

New Year's Eve should be dry!

from Cliff Mass Weather and Climate Blog http://bit.ly/2RkKWzF

Mountain Snowpack Update

Few measures of our weather/climate are more closely followed then our mountain snowpack, which brings us both recreation and water resources.

There are, of course, some concerns for this this winter, since we expect El Nino conditions for the second half of our cool season, with El Ninos generally associated with lower snowpack on April 1.  El Nino effects on our snowpack are most profound after January 1, so it is useful and important to know where we are now.

So let's take a look!

The latest USDA Snotel (December 25) reports shows near-normal conditions east of the Cascade crest, which is very important for water resources there.  Near normal in the Olympics and in eastern Oregon, and normal to above normal in the Sierra Nevada.  Colorado is in very good shape.  In contrast, the western slopes of the Cascades in Oregon and southwest WA are below normal (roughly 60-80%).  Overall, we are in decent shape.

Our snowpack has come a LONG way from the low-snowpack conditions of November and early December, when high pressure was persistent (but with more sun as a result!)  I will demonstrate this  by showing you the amount of water in the snowpack (snow water equivalent or SW) from  last night at 10 PM (left panel) versus one month ago (right panel) from the NOAA National Snow Analysis (below)   Wow...big improvement!  Enough to make skiers smile.

Compared to last year (a La Nina year), our high mountain snowpack is as good or better (see last year on December 16th below), but there was unusual lower elevation snow last year (remember the White X-Mass last year)? 

What about the forecasts for the upcoming week?    For a change, lets look at the accumulated forecasts from the European Center model.  Over the next to days,  they are going for light snow in the mountains, with a low-snow level (2-8 inches in the mountains)

 But there will be MUCH more over the next week, with as much as 2-3 feet total snowfall above roughly 5000 ft.

The bottom line is that our mountain snowpack will start the El Nino season in relatively good shape .

And skiers can get out and enjoy decent conditions, particularly in places like Mt. Baker, Crystal Mt and Whistler, which have plenty to snow.

Finally, I really enjoyed reading the ski area snow reports and particularly love the enthusiasm of the Mt. Baker folks, who are barely able to contain themselves regarding the powder (POW) on their slopes.  Check out the video below.

Dec. 24 Powder & Sunshine from Amy Trowbridge on Vimeo.



from Cliff Mass Weather and Climate Blog http://bit.ly/2BFWaVO

Mountain Snowpack Update

Few measures of our weather/climate are more closely followed then our mountain snowpack, which brings us both recreation and water resources.

There are, of course, some concerns for this this winter, since we expect El Nino conditions for the second half of our cool season, with El Ninos generally associated with lower snowpack on April 1.  El Nino effects on our snowpack are most profound after January 1, so it is useful and important to know where we are now.

So let's take a look!

The latest USDA Snotel (December 25) reports shows near-normal conditions east of the Cascade crest, which is very important for water resources there.  Near normal in the Olympics and in eastern Oregon, and normal to above normal in the Sierra Nevada.  Colorado is in very good shape.  In contrast, the western slopes of the Cascades in Oregon and southwest WA are below normal (roughly 60-80%).  Overall, we are in decent shape.

Our snowpack has come a LONG way from the low-snowpack conditions of November and early December, when high pressure was persistent (but with more sun as a result!)  I will demonstrate this  by showing you the amount of water in the snowpack (snow water equivalent or SW) from  last night at 10 PM (left panel) versus one month ago (right panel) from the NOAA National Snow Analysis (below)   Wow...big improvement!  Enough to make skiers smile.

Compared to last year (a La Nina year), our high mountain snowpack is as good or better (see last year on December 16th below), but there was unusual lower elevation snow last year (remember the White X-Mass last year)? 

What about the forecasts for the upcoming week?    For a change, lets look at the accumulated forecasts from the European Center model.  Over the next to days,  they are going for light snow in the mountains, with a low-snow level (2-8 inches in the mountains)

 But there will be MUCH more over the next week, with as much as 2-3 feet total snowfall above roughly 5000 ft.

The bottom line is that our mountain snowpack will start the El Nino season in relatively good shape .

And skiers can get out and enjoy decent conditions, particularly in places like Mt. Baker, Crystal Mt and Whistler, which have plenty to snow.

Finally, I really enjoyed reading the ski area snow reports and particularly love the enthusiasm of the Mt. Baker folks, who are barely able to contain themselves regarding the powder (POW) on their slopes.  Check out the video below.

Dec. 24 Powder & Sunshine from Amy Trowbridge on Vimeo.



from Cliff Mass Weather and Climate Blog http://bit.ly/2BFWaVO