Sunday, February 23, 2020

Strong Winds and Heavy Mountain Snows Today

A lot of weather action today.  A strong front has just moved through Puget Sound and is now pummeling the mountains and Portland (see image below for 8:11 AM).   Behind the front is cold, unstable air that is producing convection (including some thunderstorms).  This unstable air will be moving in this afternoon---so expect showers and sunbreaks over western Washington today.

The front was vigorous enough that is brought fairly strong winds, gusting to 40-50 mph in exposed locations, and was even stronger in the eastern Strait of Juan de Fuca (see below).

Why was the front (a cold front) so strong, with powerful winds (some gusting to 60 mph, heavy precipitation, hail, and even thunder?   Because it was associated with a narrow, intense cold frontal rainband-- an intense squall line, with strong thunderstorms and very large changes in temperature. 

This was made clear by the wonderful Langley Hill radar which showed the line offshore over an hour before it hit and which documented the structure immediately before hitting the south Sound (see radar image below).   You see the red line just east of Hoquiam?  THAT is the squall line.

The winds with the front have produced substantial numbers of power outages, particularly over the south sound-- including 25000 household serviced by Puget Sound Energy (see below) and 466 customers served by Seattle City Light (mainly south of the ship canal.

But the even more strong winds are yet to come.   The front is connected to a low pressure center that is now approaching northern Vancouver Island (see larger scale infrared satellite image below).

As shown by the latest UW WRF model forecasts, that low center will move westward, and as it does so, a large north-south pressure difference will develop over western Washington--which should cause a substantial acceleration of winds.  Expect gusts of 30-40 mph over much of western Washington.

Sea level pressure map at 7 AM.

Sea Level Pressure Map at 4 PM

The latest forecast of the National Weather Service HRRR (High Resolution Rapid Refresh) model for 3 PM today shows strong gusts (to 50-60 mph) along the coat and into the Strait of Juan de Fuca.   Not a good day for a ferry ride to the San Juan Islands.  And 40-50 mph gusts over southern Puget Sound
But as in late night commercials...there is more!    The cold, unstable air, driven by strong flow to the west, will be forced to rise by the Cascades and Olympics producing bountiful snow above 3000 ft---as much as 1-2 feet in places (see map of 24-h snowfall ending 4 AM Monday)

The Cascade snow could use a bit of freshening.

And then on Monday we will have clearing skies and some sun, with dry conditions in the lowlands through Friday.

Saturday, February 22, 2020

Stunning Lenticular Clouds Downstream of Mount Rainier

Native Americans, who were astute observers of the natural environment, had a saying:  "when Tahoma (Mount Rainier) has a hat, rain will soon follow."

Today it developed a hat of great beauty.

Looking out the window of my colleague, Qiang Fu, this afternoon, I saw it.  A series of stacked lenticular (lens-shaped) clouds downstream (west) of Mount Rainier (see below).  Stunning.

A bit closer view by Nicole Geer (below) shows the structure a bit better.

But why not go far closer....say from the nearby peak of Crystal Mountain, the home of a wonderful 360° high resolution live cam?

The view around 4 PM was extraordinary, with the "stacked plates" of several lenticular/mountain wave clouds clearly evident.

Pull back and you can get some perspective.  Stunning

And as the sun set and dusk settled in, the lenticular clouds remained, even as the general sky cleared a bit.  

As discussed before in this blog, lenticular clouds form as air is forced to rise by a mountain barrier, and then, like a swing, oscillates back and forth in the vertical (see figure below from my weather book).  As the air rises, it cools, and if moist enough, a lens-shaped cloud forms--with the potential to get several stacked clouds depending on the moisture structure in the vertical.  The clouds evaporate as the oscillating air sinks.

Having air close to saturation is good for the development of lenticular clouds, as is increasing wind approaching the mountain.  Both occur as weather systems approach the area--thus, there is good physical reasons for the Native American observation about a "hat" forming on the big mountain before rain falls.  In fact, the 1:30 PM infrared satellite image Friday (see below) DOES shows a weather system offshore--one that is heading towards our region.

Bottom line:  If you don't have a weather satellite handy, you can learn a great deal about future weather by being a perceptive observer.

Thursday, February 20, 2020

Why is Meteorological Spring Earlier on the West Coast Than For Much of the Nation?

Spring starts on March 20 or 21st, everyone knows that!

But that is the beginning of astronomical spring, also known as the vernal equinox--the day when the sun crosses the equator and when daylight lasts roughly twelve hours everywhere on the planet.

But astronomical spring is not the same as meteorological spring, and I would suggest that meteorological spring arrives quite early in the Northwest, generally during the third week of February.   Well before astronomical spring begins.  Furthermore, meteorological spring comes much later in the central and eastern portions of the country, where cold and snow can last well into March.

But why is this so?

Before I get into that, let me describe my definition of meteorological spring.   I would suggest that meteorological spring occurs when:

1.  The chances of a major cold wave declines profoundly.
2.  The frequency of major winter storms (midlatitude cyclones) plummets and the chance of a big storm is very low.
3.  The chance of getting a major atmospheric river and heavy rain declines precipitously.
4.  When the amount of sun increases substantially and cloudiness is often broken by sunnier periods.
5.  Leaves start growing on some trees and bushes, the number of birds increases noticeably, forsythia and crocuses begin to flower, and some insects become evident.

There is a lot of objective evidence that our spring generally starts well before March 20/21.  For example, the big snows in Seattle are in January, with amounts declining greatly in February and are very infrequent after the first week of March.

Or looking at the record low temperatures at the Seattle forecast office (blue colors), the major cold waves are in December, with some good chills extending two thirds in February, where they peter out.  After February 26th, there are no major cold excursions (lows below the upper 20s).

Multi-days of thick continuous clouds become infrequent in late February, with a major surge in solar warmth, something illustrated by the solar radiation reaching Seattle during the previous two years (see below).

So why does spring start relatively early here in western Washington/Oregon, particularly compared to the northeastern U.S.? 

Thank our mountains and the Pacific Ocean.

By the time we get into February, the sun is getting much stronger and the day is longer.  Our air is generally coming off the Pacific Ocean, which is relatively mild (45-50F) all year round.  So mild air coming in and protection from the cold air in the interior by two mountain ranges (the Cascades and Rockies), allows the stronger sun to do its job.  In addition, the jet stream begins to weaken and move northward, resulting in weaker and less frequent storms.

But the folks in the central and eastern U.S. are not so lucky!  Residual cold air from Canada can make its way down into the central and eastern U.S. well into March, providing the continued potential for cold waves and snow.  And the interaction of the cold air with warm air from the south can fuel some great coastal storms (Nor'easters) anytime in March.   In fact, some of the greatest eastern U.S. snow storms on record have occurred in March, such as the "Storm of the Century" on March 12,  1993 (see picture below).

Want to see a good recent example of cold-ridden conditions in the eastern U.S., while the West basks in warmth?  You bet you do!

Here is the forecast of heights (like pressure) and temperature around 5000 ft for next Thursday (Feb 27th). Blue is cold.  Wow   A major storm is moving up the coast, with cold, subfreezing air extending over much of the eastern U.S.  Nice spring weather for us though!

Finally, there is another sign of meteorological spring, one that is much more definitive than the weather variables I have discussed above.  Clearly, the wise folks in many supermarkets seem to know that winter weather is over....

Tuesday, February 18, 2020

A Midwinter Subtlety of Puget Sound Weather

On the surface, today was a gloriously boring weather day over western Washington.

Bright blue skies, light winds, agreeable, but cool temperatures.  A day you would think meteorologists would be taking a siesta.

But like a fine wine, Northwest weather is often best appreciated in its subtleties....and today was no different.

With clear skies and weak winds, the ground could radiate efficiently to space, and much of the region had its coldest morning in a month.  As shown by the low temperatures this (Tuesday) morning (below), temperatures ranged from the low to mid-30s near the Sound, to mid-20s in the eastern Seattle suburbs to even the single digits to a few sites  near Mt. Rainier.  Frost was found all over the region, with fog in river valleys and low spots.

This morning on the way downtown for a breakfast lecture of the wonderful CleanTech Alliance, I saw a band of clouds down the center of Lake Washington.    And reaching the 49th floor of 1201 3rd Avenue Building, I saw a line of clouds extending north-south down Puget Sound.

And I knew why is was there.....and like an experienced meteorological sommelier I was able to savior the moment.   Here is the cloud line as seen from the Space Needle PanoCam---not as dramatic a view as I had enjoyed while listening to a lecture about battery technologies, but perhaps you can see it (click on image to enlarge).

The reason for the line is that there were intersecting land breezes from both sides of the Sound.  But let me explain.

Everyone knows about sea breezes--onshore winds that occur when land gets warmer than water.  But when the opposite occurs, when the land is cooler than water, there is a rush of air from land to water called the land breeze. And such land breezes are best seen when the general winds are last night.

This morning there were land breezes on both sides of the Sound...both headed towards the center of the body of water.   This can be illustrated by a plot of the winds around 8 AM near Edmonds.
Circles indicate calm winds and air temperatures are also plotted (the observations over the water were from a Washington State ferry).  The Sound is roughly 45F this time of the year...roughly 10-15F warmer than the adjacent land.  Enough to form a weak land breeze.

As shown in the schematic below, as the land breezes convergence over the center of the Sound, air is forced to rise, forming a band of clouds.  This is what happened to today over Puget Sound and to a lesser extent over Lake Washington.  Take a careful look tomorrow may well happen again.

Sunday, February 16, 2020

U.S. Operational Weather Prediction is Crippled By Inadequate Computer Resources

U.S. global numerical weather prediction has now fallen into fourth place, with national and regional prediction capabilities a shadow of what they could be.

There are several reasons for these lagging numerical weather prediction capabilities, including lack of strategic planning, inadequate cooperation between the research and operational communities, and too many sub-optimal prediction efforts.

But there is another reason of equal importance: a profound lack of computer resources dedicated to numerical weather prediction, both for  operations and research. 

The bottom line:  U.S. operational numerical weather prediction resources used by the National Weather Service must be increased 10 times to catch up with leading efforts around the world and 100 times to reach state of the science.  

Why does the National Weather Service require very large computer resources to provide the nation with world-leading weather prediction?

Immense computer resources are required for modern numerical weather prediction.  For example, NOAA/NWS TODAY is responsible for running:

  • A global atmospheric model (the GFS/FV-3) running at 13-km resolution out to 384 hours.
  • Global ensembles (GEFS) of many (21 forecasts) forecasts at 35 km resolution
  • The high-resolution Rapid Refresh and RAP models out 36 h.
  • The atmosphere/ocean Climate Forecast System model out 9 month.s
  • The National Water Model (combined WRF and hydrological modeling)
  • Hurricane models during the season
  • Reanalysis runs (rerunning past decades to provide calibration information)
  • Running the North American mesoscale model (NAM)
  • Running the Short-Range Ensemble Forecast System (SREF)

This is not a comprehensive list.  And then there is the need for research runs to support development of the next generation systems.  As suggested by the world-leading European Center for Medium Range Weather Prediction, research computer resources should be at least five times greater than the operational requirements to be effective.

NY Times Magazine: 10/23/2016

How Lack of Computing Resources is Undermining NWS  Numerical Weather Prediction

The current modeling systems (some described above) used by the National Weather Service are generally less capable then they should be because of insufficient computer resources.  Some examples.

1.  Data Assimilation.  The key reason the U.S. global model is behind the European Center and the other leaders is because they use an approach called 4DVAR, a resource-demanding technique that involves running the modeling systems forward and backward in time multiple times.  Inadequate computer resources has prevented the NWS from doing this.

2.  High-resolution ensembles.   One National Academy report after another, one national workshop committee after another, and one advisory committee after another has told NWS management that the U.S. must have a large high-resolution ensemble system (at least 4-km grid spacing, 30-50 members) to deal with convection (e.g., thunderstorms) and other high-resolution weather features.  But the necessary computer power is not available.

European Center Supercomputer

3.  Global ensembles.  A key capability of any first-rate global prediction center is to run a large global ensemble (50 members at more), with sufficient resolution to realistically simulate storms and the major impacts of terrain (20 km grid spacing or better).  The European Center has a 52 members ensemble run at 18-km grid spacing.  The U.S. National Weather Service?  21 members at 35-km resolution.  Not in the same league.

I spend a lot of time with NOAA and National Weather Service model developers and group leaders.  They complain continuously how they lack computer resources for development and testing.  They tell me that such resource deficiency prevents them from doing the job they know they could. These are good people, who want to do a state-of-the-art job, but they can't do to inadequate computer resources.

NOAA/NWS computer resources are so limited that university researchers with good ideas cannot test them on NOAA computers or in facsimiles of the operational computing environment.  NOAA grant proposal documents make it clear:  NOAA/NWS cannot supply the critical computer resources university investigators need to test their innovations (below is quote from a recent NOAA grant document):

So if a researcher has a good idea that could improve U.S. operational weather prediction, they are out of luck:  NOAA/NWS doesn't have the computer resources to help.  Just sad.

U.S. Weather Prediction Computer Resources Stagnate While the European Center Zooms Ahead

The NOAA/NWS computer resources available for operational weather prediction is limited to roughly 5 petaflops (pflops).   Until Hurricane Sandy (2010), National Weather Service management was content to possess one tenth of the computer resources of the European Center, but after the scandalous situation went public after that storm (including coverage on the NBC nightly news), NOAA/NWS management managed to get a major increment to the current level--which is just under what is available to the European Center.

Image courtesy of Rebecca Cosgrove, NCEP Central Operations

  But the situation is actually much worse than it appears.   The NWS computer resources are split between operational and backup machines and is dependent on an inefficient collection of machines of differing architectures (Dell, IBM, and Cray).  There is a bottleneck of I/O (input/output) from these machines (which means they can't get information into and out of them efficiently), and storage capabilities are inadequate.

There is no real plan for seriously upgrading these machines, other than a 10-20% enhancement over the next few years.

In contrast, the European Center now has two machines with a total of roughly 10 pflop peak performance, with far more storage, and better communication channels into and out of the machine.

And keep in mind that ECMWP computers have far few responsibilities than the NCEP machines.  NCEP computers have to do EVERYTHING from global to local modeling, for hydrological prediction to seasonal time scales.  The ECMWF computers only have to deal with global model computing.

To make things even more lopsided, the European Center is now building a new computer center in Italy and they recently signed an agreement to purchase a new computer system FIVE TIMES as capable as their current one.

They are going to leave NOAA/NWS weather prediction capabilities in the dust.  And it did not have to happen.

And I just learned today that the UKMET office, number two in global weather prediction, just announced that it will spend 1.2 BILLION pounds (that's 1.6 billion dollars) on a new weather supercomputer system, which will leave both the European Center and the U.S. weather service behind.   U.S. weather prediction will drop back into the third tier.

Fixing the Problem

Past NOAA/NWS management bear substantial responsibility for this disaster, with Congress sharing some blame for not being attentive to this failure.  Congress has supplied substantial funding to NOAA/NWS in the past for model development, but such funding has not been used effectively.

Importantly, there IS bipartisan support in Congress to improve weather prediction, something that was obvious when I testified at a hearing for the House Environment Subcommittee last November.  They know there is a problem and want to help.

There is bipartisan support in Congress for better weather modeling

A major positive is that NOAA is now led by two individuals (Neil Jacobs and Tim Gallaudet), who understand the problem and want to fix it. And the President's Science Adviser, Kelvin Droegemeier,  is a weather modeler, who understands the problem. 

So what must be done now?

(1)  U.S. numerical prediction modeling must be reorganized, since it is clear that the legacy structure, which inefficiently spreads responsibility and support activities, does not work.  The proposal of NOAA administrator Neal Jacobs to build a new EPIC center to be the centerpiece of U.S. model development should be followed (see my blog on EPIC here).

(2) NOAA/NWS must develop a detailed strategic plan that not only makes the case for more computer resources, but demonstrates how such resources will improve weather prediction.  Amazingly, they have never done this.  In fact, NOAA/NWS does not even have a document describing in detail the computer resources they have now (I know, I asked a number of NOAA/NWS managers for it--they admitted to me it doesn't exist).

(3)  With such a plan Congress should invest in the kind of computer resources that would enable U.S. weather prediction to become first rate.  Ten times the computer resources (costing about 100 million dollars) would bring us up to parity, 100 times would allow us to be state of the science (including such things as running global models at convection-permitting resolution, something I have been working on in my research).

Keep in mind that a new weather prediction computer system would be no more expensive that a single, high tech jet fighter.  Which do you think would provide more benefit to U.S. citizens?  And remember, excellent weather prediction is the first line of defense from severe weather that might be produced by global warming.

82 million dollars a piece

(4)  Future computer resources should divided between high-demand operational forecasting, which requires dedicated large machines, and less time-sensitive research/development runs, which could make use of cloud computing.  Thus, future NOAA computer resources will be a hybrid.

(5)  Current operational numerical prediction in the National Weather Service has been completed at the NCEP Central Operations Center.  This center has not been effective, has unnecessarily slowed the transition to operations of important changes, and must be reorganized or replaced with more facile, responsive entity.

U.S. citizens can enjoy far better weather forecasts, saving many lives and tens of billions of dollars per year.   But to do so will require that NOAA/NWS secure vastly increased computer resources, and reorganize weather model development and operations to take advantage of them.

Friday, February 14, 2020

A Weak El Nino Transitioning to La Nada

During the past few months we have moved from near neutral conditions (La Nada) to a weak El Nino (warmer than normal temperatures in the central and eastern tropic Pacific)--providing some insights into the weather later this year.

Looking at the temperatures in the central tropical Pacific (the Nino 3.4 area), the water temperatures have moved from a bit cooler than normal in September to around .5C above normal.  This is a minimal El Nino.

Next, viewing water temperatures in an east-west slice of the Pacific Ocean--from the surface to about 300 meters below the surface-- show warmer than normal conditions (red/orange colors). 

The trade winds have weakened as well--another marker of El Nino.  This is a very weak, minimal El Nino.  And the strength of the signal is important.

Last month, the NOAA Climate Prediction Center was projecting that this spring we could move into neutral territory (tropical sea surface temps within .5C of normal)-- see below

And the January extended forecast from many modeling systems (see below) generally indicates neutral conditions, slightly weighted towards the warm side.  The latest European Center model is similar.

The key point in all this, is that with a weak El Nino grading to neutral (normal, La Nada) conditions in the tropical Pacific, there is no reason to expect conditions in our area to be different from normal.  They could be, of course, but the tropical Pacific will not be weighting the atmospheric dice in any direction (something that a strong El Nino or La Nina would do).

What about the BLOB?  How is it going?  The latest sea surface temperature anomaly map (difference from normal) shows cool water immediately off the West Coast, but evidence of a weak blob (1-2C above normal) off the coast.   Let's call it a junior blob...much, much weaker than the one we experienced a few years ago.

Wednesday, February 12, 2020

Extremely Favorable Water Supply Outlook for this Summer

If you enjoy drinking water, keeping your plants green, and appreciate an agricultural bounty--there is good reason to smile.  The water outlook is exceptionally favorable for this summer

As noted in my previous blog, the last two months have brought far wetter than normal conditions over the region, including a restored snowpack.

The latter is illustrated by the SNOTEL snow water equivalent map, which indicates an overall state snowpack a bit more than 100% of normal. 

The City of Seattle reservoir storage is way above normal-- in fact as high as the usual peak reservoir level in May and early June (and Seattle has been letting out plenty of water to prevent dams from being overtopped).   Similarly bountiful conditions are found for the Everett and Tacoma water systems.

But the biggest water challenge is always on the eastern slopes of the Cascades, water that supplies the huge agricultural industry of the region.    One key source of water is the Yakima River and its associated reservoir system.  As shown in the graph below, the Yakima storage system went from well below normal in November to above normal today, with the water level now as high as early April last year.

The other major sources of water for Columbia Basin agriculture is the Columbia River, whose water run-off volume for April to September is predicted to be 106% of normal by the National Weather Service's Portland River Forecast Center.  All good.

And the precipitation is not over.  The latest UW WRF model 180 h forecast of accumulated precipitation (below) suggests 2-5 inches of water content in our mountains, with several feet of snow above roughly 4000 ft.

And to top it off the latest NOAA Climate Prediction Center three months forecasts are for normal temperatures and normal to above normal precipitation over the region.

The bottom line is that we are in exceptionally good shape regarding water for the upcoming summer and early fall, with no sign of drought or water shortages.  With well-filled reservoirs, lots of snow, and much more precipitation in our near future, there is little likelihood of water issues later this year.