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/

NOAA Sand Point Facility

from Cliff Mass Weather and Climate Blog http://bit.ly/2GdqCJ2

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/

NOAA Sand Point Facility

from Cliff Mass Weather and Climate Blog http://bit.ly/2GdqCJ2

Heavy Convergence Zone Rainfall Inundates the Central WA Cascades

There has been an extraordinary amount of rainfall on the western slopes of the Washington Cascades, and the origin of the heaviest areas is the Puget Sound convergence zone, coupled with the return of wet weather to the region.

As a result, reservoirs providing water to Seattle, Everett, Tacoma, and the Yakima Valley are rapidly filling, further lessening any water issues this summer.

Many of you have some acquaintance with the Puget Sound convergence zone, which is associated with westerly/northwesterly air flow that is deflected around the Olympics and then converges over Puget Sound (see figure). 

Where the air converges, one gets upward motion and enhanced precipitation, as illustrated by the radar image yesterday at 415AM. Note the relatively narrow area of rainfall stretching southeastward from the eastern side of the Olympics--that is the result of the Puget Sound convergence zone.

But there is an important subtlety apparent in the radar image:  the impact of the convergence zone extends beyond the lowlands of Puget Sound, well into the Cascades.   Frequently, the enhancement of precipitation extends to the Cascade crest and beyond. 

Puget Sound convergence zones are most frequent during the spring, since this is the time of the year when westerly/northwesterly flow is most often observed.  And the unstable air of this season, produced by the increased warmth of the sun, produces a lot of precipitation for even small amount of low-level convergence.

During the past week, we have had several convergence zone events that have produced HUGE amounts in the central WA Cascades.  This is illustrated by the 1-week totals ending this morning.

Several locations on the western side of the Cascades near Snoqualmie pass have gotten over SIX inches of precipitation. Some 7-8 inches.  Sometimes the convergence zone sets up over Snohomish County and you will notice some big values up there as well.

Worried about water in Seattle?  Here is the rainfall at Chester Morse Lake--the largest reservoir for Seattle--over the past week.  About 8 inches.

And as a result, the lake level has gone up substantially (see below)

The impacts of the convergence zones have also extended across the Cascades, helping to fill some of the key reservoirs of the Yakima River, such as Lake Keechelus (see below), which was below normal, but will soon reach normal levels during the next week.

The latest model runs suggest the bountiful precipitation is not over, with substantial precipitation over the Cascades and Olympics.  The forecast for the next 72-h shows several includes at higher elevation...some as high as 2-4 inches over the period..  You might want to delay any hikes on the western side of the Cascades or head over to eastern WA.

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

Heavy Convergence Zone Rainfall Inundates the Central WA Cascades

There has been an extraordinary amount of rainfall on the western slopes of the Washington Cascades, and the origin of the heaviest areas is the Puget Sound convergence zone, coupled with the return of wet weather to the region.

As a result, reservoirs providing water to Seattle, Everett, Tacoma, and the Yakima Valley are rapidly filling, further lessening any water issues this summer.

Many of you have some acquaintance with the Puget Sound convergence zone, which is associated with westerly/northwesterly air flow that is deflected around the Olympics and then converges over Puget Sound (see figure). 

Where the air converges, one gets upward motion and enhanced precipitation, as illustrated by the radar image yesterday at 415AM. Note the relatively narrow area of rainfall stretching southeastward from the eastern side of the Olympics--that is the result of the Puget Sound convergence zone.

But there is an important subtlety apparent in the radar image:  the impact of the convergence zone extends beyond the lowlands of Puget Sound, well into the Cascades.   Frequently, the enhancement of precipitation extends to the Cascade crest and beyond. 

Puget Sound convergence zones are most frequent during the spring, since this is the time of the year when westerly/northwesterly flow is most often observed.  And the unstable air of this season, produced by the increased warmth of the sun, produces a lot of precipitation for even small amount of low-level convergence.

During the past week, we have had several convergence zone events that have produced HUGE amounts in the central WA Cascades.  This is illustrated by the 1-week totals ending this morning.

Several locations on the western side of the Cascades near Snoqualmie pass have gotten over SIX inches of precipitation. Some 7-8 inches.  Sometimes the convergence zone sets up over Snohomish County and you will notice some big values up there as well.

Worried about water in Seattle?  Here is the rainfall at Chester Morse Lake--the largest reservoir for Seattle--over the past week.  About 8 inches.

And as a result, the lake level has gone up substantially (see below)

The impacts of the convergence zones have also extended across the Cascades, helping to fill some of the key reservoirs of the Yakima River, such as Lake Keechelus (see below), which was below normal, but will soon reach normal levels during the next week.

The latest model runs suggest the bountiful precipitation is not over, with substantial precipitation over the Cascades and Olympics.  The forecast for the next 72-h shows several includes at higher elevation...some as high as 2-4 inches over the period..  You might want to delay any hikes on the western side of the Cascades or head over to eastern WA.

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

No Reason to Worry Yet About Summer Drought in the Northwest

The second half of March was very dry.  No doubt about it.

As a result, Washington snowpack has declined, ranging from roughly 60-90% of normal.

And a nervousness has spread in the media and among some politicians, some talking about summer drought, increased wildfire risk, and degraded agriculture.

My reading:  the current situation is NOT serious, that the snowpack is not that low, that our reservoirs are in good shape, and that substantial April rain/snow will ensure that we go into this summer in reasonable shape.

A sample is shown below, ranging from a drought emergency to predictions of smoke-filled skies and reduced irrigation water.

Now, let's look at the facts on the ground and consider the forecasts for the next week or so.    April plays a critical role regarding summer drought in the Northwest.   If April is dry, the summer desiccation season gets a head start,  leading to enhanced drying and a too rapid loss of snowpack.  But a wet April is a boon, keeping the area moist and the snowpack in place.

So where are we right now? 
The snowpack is fine along the southern portion of the state. OK, over NW Washington (low 80s%), decent over the Olympics (79%), but only around 65% on the western side of the north/central Cascades. 

Some media outlets are comparing this to 2015...but it is NOTHING like 2015, when the early April snowpack percentiles were in the single digits in some locations (see below).

Unlike 2015, April this year should bring more snow.  In fact, the National Weather Service is going for substantial amounts (up to a few feet) and they have winter weather advisory out right now.

The WRF model forecast for accumulated snowfall for the week shows several feet of snow in the Cascades, just where it is low now.  Expect the snowpack numbers to improve substantially.

And there will be plenty of total precipitation over the region during the same period, including eastern Washington.

Reservoirs?

Even before the recent precipitation, Seattle's reservoirs were just a bit below normal:

The critical Yakima system is modestly below normal to starting to move towards normal:

The bottom line is that this year is very typical for a weak to moderate El Nino year, with snowpack and precipitation a bit below normal, but nothing serious.

from Cliff Mass Weather and Climate Blog http://bit.ly/2uXs3Gf

No Reason to Worry Yet About Summer Drought in the Northwest

The second half of March was very dry.  No doubt about it.

As a result, Washington snowpack has declined, ranging from roughly 60-90% of normal.

And a nervousness has spread in the media and among some politicians, some talking about summer drought, increased wildfire risk, and degraded agriculture.

My reading:  the current situation is NOT serious, that the snowpack is not that low, that our reservoirs are in good shape, and that substantial April rain/snow will ensure that we go into this summer in reasonable shape.

A sample is shown below, ranging from a drought emergency to predictions of smoke-filled skies and reduced irrigation water.

Now, let's look at the facts on the ground and consider the forecasts for the next week or so.    April plays a critical role regarding summer drought in the Northwest.   If April is dry, the summer desiccation season gets a head start,  leading to enhanced drying and a too rapid loss of snowpack.  But a wet April is a boon, keeping the area moist and the snowpack in place.

So where are we right now? 
The snowpack is fine along the southern portion of the state. OK, over NW Washington (low 80s%), decent over the Olympics (79%), but only around 65% on the western side of the north/central Cascades. 

Some media outlets are comparing this to 2015...but it is NOTHING like 2015, when the early April snowpack percentiles were in the single digits in some locations (see below).

Unlike 2015, April this year should bring more snow.  In fact, the National Weather Service is going for substantial amounts (up to a few feet) and they have winter weather advisory out right now.

The WRF model forecast for accumulated snowfall for the week shows several feet of snow in the Cascades, just where it is low now.  Expect the snowpack numbers to improve substantially.

And there will be plenty of total precipitation over the region during the same period, including eastern Washington.

Reservoirs?

Even before the recent precipitation, Seattle's reservoirs were just a bit below normal:

The critical Yakima system is modestly below normal to starting to move towards normal:

The bottom line is that this year is very typical for a weak to moderate El Nino year, with snowpack and precipitation a bit below normal, but nothing serious.

from Cliff Mass Weather and Climate Blog http://bit.ly/2uXs3Gf

Bountiful Precipitation and Full Reservoirs in California

It was not that long ago, that some folks were wringing their hands about drought in California, claiming that normal rains were a thing of the past.  The NY Times and other outlets warned of "permanent" and "unending" drought fueled by global warming.

2013-2015 were dry years, but 2017 was extremely wet, 2018 was near normal, and 2019 is turning out to be a real soaker.    The official U.S. Drought Monitor, which often lags behind facts on the ground,  officially removed drought status from California this winter.

This winter, the water situation is extraordinarily good for virtually all of California, with their very large reservoir system storing much more water than normal.   Let's examine the situation.

Here is the difference from normal of the accumulated precipitation over the past six months.  Nearly the entire southwest U.S. was above normal, with parts of California being 8-20 inches above normal...that is a lot in California.

Water storage is everything in California, and unlike Washington State, they have multi-year storage capacity.  Why?  Because historically California experiences more variation between wet and dry years than the more reliably wet Pacific Northwest. 

The current reservoir conditions are excellent, with all of the major reservoirs being well above normal.  Some are even near capacity (e.g., San Luis and Lake Shasta).

The other major water storage system is the snowpack....and CA has a HUGE snowpack this year, averaging about 165% of normal (see below).

Streamflow?   No worries.  Streams are running much above normal or high over the northern portion of the state ( blue and black colors) and near normal over most of the southern half.

Surface soil moisture is above normal for most of the state (not shown). 

The bottom line of all this is that California has had an extraordinarily moist winter (and a very wet March) and there will be plenty of water for the urban centers and agriculture this year. 

To put things in perspective, below is the California precipitation for November-February 1920-2019 using the NOAA/NWS climate division dataset.  March 2010 was not ready yet. 

The first thing you notice is that there is virtually no long-term trend.  Nada.   There are drier years (like 2013-2015) and wetter periods.  2019 was above normal but not exceptional.   If March was available, the current winter would have been one of the wetter ones.

This lack of trend in CA winter precipitation is consistent with most climate models simulations I have seen, which suggest no decline in precipitation for central and northern CA under global warming (see a sample from the UW high-resolution climate simulation project I am involved with).  In fact, precipitation over the northern portion of CA might even increase.

But that does not mean that California is entirely out of the woods.  Temperatures WILL rise under global warming and that will increase demand for water, particularly for agriculture.    And California is currently "mining" its ground water at an unsustainable pace.    So adaptations will have to take place, like growing less water intensive crops (e.g., almonds and cotton), using better irrigation technologies, and increasing the use of desalination plants on the coast. 

California will not be facing an "existential" threat under global warming, but will have to take reasonable steps to adapt to a warming climate.



from Cliff Mass Weather and Climate Blog http://bit.ly/2D4GI7b