Sad News: No More BLOB

A lot of folks are interested in the BLOB, the colorfully named area of warm water that periodically appears over the northeast Pacific.  And there is major BLOB news.... it is gone.  Let me describe the sad news.

Starting the autumn, the BLOB was relatively weak.  To illustrate, here is the sea surface temperature anomaly (difference from normal) for the end of October--as much as 2-3C warmer than normal!  This was associated with an area of persistent high pressure over the northeast Pacific.

But compare that situation to two days ago.  The BLOB is essentially gone, with an area of cooler than normal water developing.  Only immediately along the coast is the water temperature slightly above normal.

What killed the BLOB?   Persistent storminess over the northeast Pacific, something that is no surprise to the storm-battered residents of the Pacific Northwest. 

Here is the proof: the anomaly of the mid-tropospheric (500 hPa) heights from normal for the last 30 days.  Blue and purple indicate lower than normal heights, which is associated with more and deeper low-pressure centers, which in turn cause strong winds.  A big area of lower heights (or equivalently pressure) was found over the NE Pacific.

The BLOB forms with persistent high pressure that is associated with weaker winds.  Weak winds do not mix the upper ocean as much as strong wind, thus bringing up less cool water from below.   Persistent low pressure, with higher winds, are good at mixing, thus reducing water temperatures.  That is what has been going on lately.  There is no reason to expect that the BLOB is a sign of global warming.

So during this holiday season, your pleasure in enjoying a few day break may be tempered, at least a little bit, by a touch of sadness about the passing of our our old friend, the BLOB.  For myself, I find solace knowing that the BLOB  is sleeping, knowing that it will surely awake and return one day.

from Cliff Mass Weather and Climate Blog http://bit.ly/2GDwY87

A Beautiful Storm Approaches the West Coast

The third major Pacific cyclone is now approaching the West Coast, this time heading farther north towards central British Columbia.  As a result, the wind effects will be lessened over Washington State compared to the last storm.

But forgetting about the wind and rain, there is something else about this storm:  it is beautiful in shape and structure--a gorgeous spiral of clouds and complex structures.   Let me show you.

Let's start with the GOES-17 visible image around 3 PM  (below).  Huge storm, with the frontal cloud bands spiraling into the low center.    And if you look closely, the can see the mottled/speckled clouds of cold air instability spiraling into the low center.  Very nice.

But we can do better than that:  here is the view of the higher-resolution MODIS satellite around noon.  Just stunning.  The low center is in the middle of the spiraling clouds.

A closer look at the low center is found below. You can see the frontal cloud band (solid layer) and and instability clouds spiraling around on the outside.

By why stop there looking at this beautiful storm?   Here is the water vapor imagery, showing you the amount of water vapor in the upper troposphere (roughly 20,000-30,000 ft). White means a lot of water vapor, dark means little in that layer.  Cool, dry air is spiraling into the low center.  Exquisite! 

To serve as a comparison, here is the 1800 UTC (10 AM) sea level pressure and frontal analysis provided by the Weather Service;  they estimated the central pressure as 980 hPa--a strong storm, but not an equal for any of greats (like the Inauguration Day-1990 or Chanukah Eve-2006 storms).

The model wind gust forecast for 1 PM today shows two areas of strong winds, on ewith the main front, that was battering the coastal waters at that time, and the second in the region just south of the low.

 By 1 AM Sunday, the low center will be approaching landfall, just north of Vancouver Island, with the strong winds to its south.   Just some spare change for us, here in WA State.  Which is fine.

from Cliff Mass Weather and Climate Blog http://bit.ly/2V8DYgv

A Beautiful Storm Approaches the West Coast

The third major Pacific cyclone is now approaching the West Coast, this time heading farther north towards central British Columbia.  As a result, the wind effects will be lessened over Washington State compared to the last storm.

But forgetting about the wind and rain, there is something else about this storm:  it is beautiful in shape and structure--a gorgeous spiral of clouds and complex structures.   Let me show you.

Let's start with the GOES-17 visible image around 3 PM  (below).  Huge storm, with the frontal cloud bands spiraling into the low center.    And if you look closely, the can see the mottled/speckled clouds of cold air instability spiraling into the low center.  Very nice.

But we can do better than that:  here is the view of the higher-resolution MODIS satellite around noon.  Just stunning.  The low center is in the middle of the spiraling clouds.

A closer look at the low center is found below. You can see the frontal cloud band (solid layer) and and instability clouds spiraling around on the outside.

By why stop there looking at this beautiful storm?   Here is the water vapor imagery, showing you the amount of water vapor in the upper troposphere (roughly 20,000-30,000 ft). White means a lot of water vapor, dark means little in that layer.  Cool, dry air is spiraling into the low center.  Exquisite! 

To serve as a comparison, here is the 1800 UTC (10 AM) sea level pressure and frontal analysis provided by the Weather Service;  they estimated the central pressure as 980 hPa--a strong storm, but not an equal for any of greats (like the Inauguration Day-1990 or Chanukah Eve-2006 storms).

The model wind gust forecast for 1 PM today shows two areas of strong winds, on ewith the main front, that was battering the coastal waters at that time, and the second in the region just south of the low.

 By 1 AM Sunday, the low center will be approaching landfall, just north of Vancouver Island, with the strong winds to its south.   Just some spare change for us, here in WA State.  Which is fine.

from Cliff Mass Weather and Climate Blog http://bit.ly/2V8DYgv

The December 20 Windstorm and the Start of Winter

Yesterday, we had another moderate windstorm over western Washington, one that had even greater effects over British Columbia.   Gusts reached 70-75 mph in "favored" locations and about 300,000 customers lost power in the region.  Even my home went dark.

The National Weather Service surface analysis for 10 AM yesterday showed a fairly deep system (978 hPa) moving northeast into Vancouver Island.

This hand analysis does not accurately show the detailed pressure structure of the storm.  A far better view comes from a short-term, and thus highly accurate, model forecast shown below (6-h prediction by the UW high-resolution WRF predictions).  The solid lines are isobars, lines of constant pressure, and you will note an intense change or gradient of these lines south and west of the low center. 
Classic for a strong marine cyclone.   Strong pressure gradients suggest strong winds.  And that area of intense pressure gradient moved across northwestern WA during the subsequent hours, producing the powerful winds.

How strong?

Gusts reaching 78 mph at Destruction Is along the central WA coast and 70 mph at Race Rocks in the Strait of Juan de Fuca.  Similar winds from a downslope mountain wave on the Olympics.    And gusts to around 50 mph for exposed locations in central Puget Sound.

But lets look at the max gusts for a far smaller area....around Seattle. Around 50 mph for exposed locations (e.g., West Point or in the center of the Evergreen Pt. floating bridge), but locations with poor exposure, bad instrument placement, or poor instruments had far less wind (less than 20 mph).

Winds are a very difficult measurement and unfortunately many wind observations are unreliable. 

Surface winds should be measured at 10 meters (about 30 feet) in open area.  Not on a house.  Not with trees nearby.  Many sensors do not have such exposure, although the official airport stations should all be reliable.  A colleague of mine, Professor Bob Fovell of University of Albany and student Alex Gallagher, just published a very nice paper showing that many cooperative wind observation networks are nearly useless of determined winds during Thomas Fire  (a Santa Ana event).

Today is the start of winter and I have some good news....no big storms in the forecast! 
No rain and partly cloudy today.   Perfect weather for cleaning up debris and doing that last minute holiday shopping.

And remember, we are in an El Nino winter and the impacts of the warm Pacific water (lesser storms, warmer temps) tends to hit after New Years.

from Cliff Mass Weather and Climate Blog http://bit.ly/2V1X6wv

The December 20 Windstorm and the Start of Winter

Yesterday, we had another moderate windstorm over western Washington, one that had even greater effects over British Columbia.   Gusts reached 70-75 mph in "favored" locations and about 300,000 customers lost power in the region.  Even my home went dark.

The National Weather Service surface analysis for 10 AM yesterday showed a fairly deep system (978 hPa) moving northeast into Vancouver Island.

This hand analysis does not accurately show the detailed pressure structure of the storm.  A far better view comes from a short-term, and thus highly accurate, model forecast shown below (6-h prediction by the UW high-resolution WRF predictions).  The solid lines are isobars, lines of constant pressure, and you will note an intense change or gradient of these lines south and west of the low center. 
Classic for a strong marine cyclone.   Strong pressure gradients suggest strong winds.  And that area of intense pressure gradient moved across northwestern WA during the subsequent hours, producing the powerful winds.

How strong?

Gusts reaching 78 mph at Destruction Is along the central WA coast and 70 mph at Race Rocks in the Strait of Juan de Fuca.  Similar winds from a downslope mountain wave on the Olympics.    And gusts to around 50 mph for exposed locations in central Puget Sound.

But lets look at the max gusts for a far smaller area....around Seattle. Around 50 mph for exposed locations (e.g., West Point or in the center of the Evergreen Pt. floating bridge), but locations with poor exposure, bad instrument placement, or poor instruments had far less wind (less than 20 mph).

Winds are a very difficult measurement and unfortunately many wind observations are unreliable. 

Surface winds should be measured at 10 meters (about 30 feet) in open area.  Not on a house.  Not with trees nearby.  Many sensors do not have such exposure, although the official airport stations should all be reliable.  A colleague of mine, Professor Bob Fovell of University of Albany and student Alex Gallagher, just published a very nice paper showing that many cooperative wind observation networks are nearly useless of determined winds during Thomas Fire  (a Santa Ana event).

Today is the start of winter and I have some good news....no big storms in the forecast! 
No rain and partly cloudy today.   Perfect weather for cleaning up debris and doing that last minute holiday shopping.

And remember, we are in an El Nino winter and the impacts of the warm Pacific water (lesser storms, warmer temps) tends to hit after New Years.

from Cliff Mass Weather and Climate Blog http://bit.ly/2V1X6wv

Another windstorm will hit the Northwest on Thursday

Mother nature is throwing everything in her cupboard against us this week.   We had the first major Pacific cyclone/windstorm, lots of snow in the mountains, heavy mountain rains, a downslope windstorm event on the Olympics, and an EF1-2 tornado.   Meteorological heaven for those who like a good storm.

But the strong storms are not over yet, and Thursday will bring another strong Pacific cyclone to our coast, with strong winds and power outages for many. 

Here are the latest forecasts from the UW WRF model.  We are close enough in time that this evolution should be fairly accurate (and the spread of the ensemble is not that great now).

Let's start with the forecast sea level pressure map at 1 AM Thursday.  A 991 hPa low center is found offshore, with a strong pressure gradient (large change in pressure with distance) off the Northwest Coast.  Thus, strong coastal winds (probably gusting to 30-60 knots) would be in place over the water at that time.

The storm, moving northeast makes landfall on Vancouver Island, and is over southeast BC by 1 PM Thursday afternoon (see below).  The region of strong pressure gradient is over western WA at this time, and particularly NW WA.  Winds would be revving up over inland western WA by this time, peaking a few hours later over Puget Sound.

Let me show you high-resolution forecasts of the surface winds. At 4 AM, wind gusts will have reached 50-60 knots, along the coast, and nearly as high near Victoria and the southern San Juans.  Also note a strong Olympic mountain wave, with strong flow descending the northern slopes of the Olympics.  Deja vu all over again.

By 10 AM (18 UTC), winds rev up in Puget Sound (gusting to 30- 40 knots), with big winds remaining along the coast and San Juans.

 Then the final stage of the wind action, as the low moves by to the northeast, a strong onshore pressure gradient will develop and a westerly wind surge will occur in the Strait of Juan de Fuca (see map for 4 PM on Thursday).   If you were planning a ride on the Victoria Clipper between Seattle and Victoria tomorrow afternoon, bring plenty of Dramamine--it will be a very rough ride.

This event probably won't be more intense that last Friday's windstorm over Puget Sound, but potentially stronger over NW WA and the coast.  There is some variability in the exact landfall position, and  small error could have a big impact on the winds, so keep watching the forecasts. Make sure your batteries are fresh, your barbecue has gas, and your smarphone is charged.

from Cliff Mass Weather and Climate Blog https://ift.tt/2CmvNpc

Another windstorm will hit the Northwest on Thursday

Mother nature is throwing everything in her cupboard against us this week.   We had the first major Pacific cyclone/windstorm, lots of snow in the mountains, heavy mountain rains, a downslope windstorm event on the Olympics, and an EF1-2 tornado.   Meteorological heaven for those who like a good storm.

But the strong storms are not over yet, and Thursday will bring another strong Pacific cyclone to our coast, with strong winds and power outages for many. 

Here are the latest forecasts from the UW WRF model.  We are close enough in time that this evolution should be fairly accurate (and the spread of the ensemble is not that great now).

Let's start with the forecast sea level pressure map at 1 AM Thursday.  A 991 hPa low center is found offshore, with a strong pressure gradient (large change in pressure with distance) off the Northwest Coast.  Thus, strong coastal winds (probably gusting to 30-60 knots) would be in place over the water at that time.

The storm, moving northeast makes landfall on Vancouver Island, and is over southeast BC by 1 PM Thursday afternoon (see below).  The region of strong pressure gradient is over western WA at this time, and particularly NW WA.  Winds would be revving up over inland western WA by this time, peaking a few hours later over Puget Sound.

Let me show you high-resolution forecasts of the surface winds. At 4 AM, wind gusts will have reached 50-60 knots, along the coast, and nearly as high near Victoria and the southern San Juans.  Also note a strong Olympic mountain wave, with strong flow descending the northern slopes of the Olympics.  Deja vu all over again.

By 10 AM (18 UTC), winds rev up in Puget Sound (gusting to 30- 40 knots), with big winds remaining along the coast and San Juans.

 Then the final stage of the wind action, as the low moves by to the northeast, a strong onshore pressure gradient will develop and a westerly wind surge will occur in the Strait of Juan de Fuca (see map for 4 PM on Thursday).   If you were planning a ride on the Victoria Clipper between Seattle and Victoria tomorrow afternoon, bring plenty of Dramamine--it will be a very rough ride.

This event probably won't be more intense that last Friday's windstorm over Puget Sound, but potentially stronger over NW WA and the coast.  There is some variability in the exact landfall position, and  small error could have a big impact on the winds, so keep watching the forecasts. Make sure your batteries are fresh, your barbecue has gas, and your smarphone is charged.

from Cliff Mass Weather and Climate Blog https://ift.tt/2CmvNpc