Island Clouds

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Can an island that reaches a few hundred feet in elevation create its own clouds?   The answer is yes, and some wonderful video of southern Whidbey Island yesterday afternoon shows the action.

Image from the video at 1:12 PM Feb. 12

 The video was provided by Greg Johnson, who maintains the excellent skunkbayweather web site.  He has two cams looking northeastward towards Whidbey Island from his home in Skunk Bay (Hansville) on the Kitsap Peninsula (see map).


The temperature and dew point at Skunk Bay (see graphic) and other nearby sites (e.g., Wahl Rd on Whidbey Is, also shown) were close but not at saturation (the dew point was a few degrees less than the temperature).
Whidbey Island is about 300 ft high for the peninsula in view, with a relatively abrupt cliff facing the southeast. (see blow-up of the terrain below) The winds were from the southeast over the area and so

air was forced up quickly along that share..  As the air was forced to rise, it cooled (air moving from higher pressure to lower pressure expands and cools).  The temperature fell to the dew point and the air became saturated, producing a cloud.  As shown in the picture above, and the video below, the cloud was not only maintained over the land, but streamed downwind of the island.

How much will air cool moving up a slope?   If we assume that the air rose 100 meters (328 ft) and assume the dry adiabatic lapse rate (9.8 C per km, the rate that unsaturated air parcels cool when they are forced to rise), we get a decrease of .98C or 1.8F, which was enough to bring the temperature down to the dew point.

Greg Johnson produced a wonderful slow-motion video of the event; click on the image to view it yourself.


If you want real visual treat, check out his melding of TWO cams into one wide image--it doesn't get much better than that! (click on image below):

 
We may not have gotten megastorms this season like the NE U.S., but our weather has its own fascinations and subtleties.  Like the subtle flavors and accents of a fine wine compared to the overwhelming flavors of a highly sweetened soft drink.   Northwesterners have sophisticated meteorological palates.

The Most Boring Winter in Seattle History

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Many of you have complained about this winter.  That the weather has been entirely boring:  no snowstorms, no real windstorms, no extreme temperatures, no pineapples expresses,  no nothing.

 To try to quantify our plight, I and other local weather scientists have developed a new, and I hope, authoritative measure of interesting weather here in Seattle:
The Seattle Winter Excitement Index (SWEI).  (correct pronunciation is "swee")

SWEI is calculated over the core of Seattle's winter (Nov. 15-Feb 15) and is the sum of several components parts:

(1) The number of days the temperature exceed 60F or drops below 25F.
(2) The number of days with two inches or more of precipitation.
(3) The number of days with sustained winds of 30 kt or more.
(4)  The number of months with more than 1 inch of snowfall.

All inputs are from Seattle Tacoma Airport.  I should note there are rigorous reasons for each of the above criteria.  For example, many official groups (like this National Weather Service site) consider that hard freezes occur below 25F.   Plants die.  Local meteorologists note that wind damage often begins when sustained winds hit 30 kt or more.  And local mayors confirm that even 1 inch over a month brings tension, excitement, and danger to local roadways.  Folks, this is rigorous science.


I asked my department's star data analyst, Neal Johnson, to run the numbers for the entire record (1948- today) at Seattle Tacoma Airport, the main climatological site for western Washington.

The results are in.  Be prepared for sobering news.

This winter is the most boring and uneventful based on the SWEI index described above.  Actually, we are tied for most boring with 1963-1964.  Specifically, 2012-13 and 1963-1964 had the lowest values of the SWEI index.

Only old-timers who can remember back nearly FIFTY YEARS can wax nostalgic about such a boring winter.  For the quantitative among you, here are the ranks of the top boring years (a lot of ties)

19631115-19640215   1
20121115-20130215   1
20001115-20010215   2
20011115-20020215   2
20021115-20030215   2
19601115-19610215   3
19751115-19760215   3
19821115-19830215   3
19911115-19920215   3
19971115-19980215   3
19991115-20000215   3

The signs of profoundly boring weather is everywhere.  For example, the latest snow pack map shows that, well, we are averaging near 100% (see below).  Big surprise.


Or plot the cumulative precipitation at Sea Tac and compare to climatological values over the last three months (see graphic).  We come out very slightly below normal.  And no big one-day precipitation event.  Long periods of virtually nothing.  Yawn.

The best we could do in extreme weather this year was an extended period of low-clouds/temperature-inversion and one incident of high tides, the later mainly caused by astronomical features and a modest low.  Not good enough. No wonder the Weather Channel has ignored us.  Jim Cantore will travel elsewhere.

Extreme Weather in Seattle

The natural question of many of you is why?  What convergence of unusual events, what causative factors can produce such an anomaly?

 I do not have an answer.  

But I have heard that some folks at the web sites Skeptical Science and 350.org have suggested that such extremely boring weather is "consistent" with what one might expect from increasing greenhouse gases in the atmosphere.  Time will tell.

I realize that there is some danger in writing this particular blog.   Like putting a red flag in front of a meteorological bull.   But I am willing to take the risk and quite honestly we need some excitement around here.

Misunderstood Probablility

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Probability of precipitation is given on virtually every weather forecast, but many people don't really understand what it is and where it comes from.

Let's test your knowledge of this important weather concept.

A probability of precipitation of 30% means:

(1)  One expects precipitation for 30% of the time.
(2)  One expects precipitation over 30% of the area.
(3)   There is a 30% chance of precipitation at some point over a particular period.
(4)  That it will precipitate 30% of the time over 30% of the area over a particular period.

Time's up.  Write it down.  The answer is number three. Probabilities are always given for a point in space over a standard period (most frequently over 12 hr time chunks).  So at that location over the specified period for similar weather conditions, we would expect it to precipitate 3 out of 10 times.
If you got it wrong don't worry about it....a lot of people do.   Consider the study by some European scientists in the journal Risk Analysis (found here).  They questioned folks in Amsterdam, Athens, Berlin, Milan, and New York about what a “30% chance of rain tomorrow” meant.  Only in New York did the majority of the survey group supply the correct answer.  You have got to respect those New Yorkers; they walk and talk fast, but boy do they know their probabilities.  In the European cities, the preferred (and incorrect) interpretations were that it will rain tomorrow “30% of the time,” followed by “in 30% of the area.”   So much for European sophistication.

Does being precipitation soaked give Northwesterners  more insight into precipitation probabilities?   University of Washington psychology professor and expert in weather information interpretation, Dr. Susan Joslyn, has completed several studies encompassing hundreds of students to answer this very question.   As described in an article in the Bulletin of the American Meteorological Society (found here), she and her colleagues found that only roughly 50% of the sodden UW students got the right answer.  Disappointing!
One more interesting question.  When was the term probability first used in a weather forecast?  The amazing answer:  the very first forecast!

Following the signing by President Ulysses S. Grant of an authorizationto establish a system of weather observations and warnings of approachingstorms, on February 19, 1871, Cleveland Abbe issued the first “official” public WeatherSynopsis and Probabilities based on observations taken at 7:35 a.m. that day: 

"Synopsis forpast twenty-four hours; the barometric pressure had diminished in the southernand Gulf states this morning; it has remained nearly stationary on the Lakes. Adecided diminution has appeared unannounced in Missouri accompanied with arapid rise in the thermometer which is felt as far east as Cincinnati; thebarometer in Missouri is about four-tenths of an inch lower than on Erie and onthe Gulf. Fresh north and west winds are prevailing in the north; southerlywinds in the south. Probabilities: it is probable that the low pressure in Missouri will make itself feltdecidedly tomorrow with northerly winds and clouds on the Lakes, and brisksoutherly winds on the Gulf."

For his insistence in using the term probabilities, Cleveland Abbe was given the name "Old Probs."  In a future blog, I will describe how meteorologists come up with probabilities.  Be prepared, this is the meteorological version of sausage making.

"Old Probs" Cleveland Abbe:  The first official U.S. weather forecaster!

 

Weather Returns to the Northwest

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I knew it was a mistake to blog about boring weather....

For those of us who have forgotten what Northwest weather can bring, we are about to get a reminder.

But before I talk about that, let me invite you to the Northwest Weather Workshop, which will be taking place in a little over a week (March 1-2).  This is the big local meeting for those interested in Northwest weather, with a wide variety of talks, most of which are accessible to those who don't have a formal meteorological background.  It starts at 1 PM on Friday, March 1 and ends Saturday around 3 PM.  We have a very nice banquet at Talaris Conference Center in Seattle, with a special speaker (Susan Joslyn, a UW psychology professor who specializes in how weather information is communicated.)   More information is found here.   You need to register if you would like to go!

 Now the coming weather...

The upper level ridge that has been over or just east of us has faded and strong flow from the west is now headed towards are region.  To illustrate, here is the  upper level (500 hPa, roughly 18,000 ft) flow (solid lines are the heights of the 500 hPa pressure surface) for Friday morning.  Winds are nearly parallel to the lines and are stronger when the lines are closer together.  A series of disturbances is lined up to move into our region.

In concert with the approaching disturbances, this strong incoming flow (also known as the jet stream) will be bringing a current of high amounts of moisture, moisture that was injected northward over the western Pacific.  Here is the forecast moisture distribution on Friday morning.  Red indicates high values.

Expect plenty of rain and snow.  Here are the total precipitation and snowfall for the 72 hr beginning Wed. morning at 4 AM.  2-5 inches on the western slopes over most the windward (western) slopes of the coastal and Cascade Mountains.   Yes...not a record atmospheric river...but a good soaker.

Temperatures will be cool enough that a lot of this precipitation will be snow in the mountains.  We are talking about 2-3 feet of snow, particularly above roughly 3500 ft.

And winds?  Expect strong winds over the eastern Pacific and Northwest Washington on Friday as a strong low moves to our north.  (see map of sustained winds below).  30 kts plus sustained winds along and off the coast. Considerably stronger gusts.

And you like waves?  With a strong weather system on Friday and powerful NW winds behind, there will be substantial waves on the ocean beaches (see graphic valid Saturday morning).  Yellow indicate waves of 8-9 meters, 25-30 ft.   Good wave watching on Saturday afternoon at Westport.

So enjoy the active weather...nothing that will cause a lot of damage, but enough to remain us that Northwest weather can be fun.

Radar, Wind, and Snow

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The front has gone by, the winds have lessened, and heavy snow is falling on the western slopes of the Cascades.    But first, let me answer a frequently asked question:  what is the persistent echo seen just offshore of Hoquiam in many images from the Langley Hill radar? (see below).   This pattern is seen persistently in the lower radar scans and looks like a half circle.    The answer: the lower portion of the radar beam is hitting the surface and reflecting back to the radar, which is located a few miles northwest of Hoquiam.   Such a phenomenon is known as ocean or sea clutter.   The image below is from the half-degree elevation angle scan of the Langley radar, which means the center of the beam is a half-degree above the horizontal.  The width of the beam is roughly 1 degree, so the lower portion of the beam skims the surface in the vicinity of the radar.
Some of you might ask, doesn't the radar also hit the ground and terrain?  Why don't we see a return there as well?  The answer is that you would except for the fact the radar has ground clutter suppression software that subtracts that out.   Land and mountains stay put and so the radar can be trained to ignore returns from them. Not so easy with an ocean surface with waves and swell.  We knew we would get some sea clutter with the new radar, but it is a small price to pay for the capability to see farther out into the Pacific.  In fact, due to the intercession of Senator Cantwell, our radar has the capability to scan lower than any other NWS radar in the country:  .15 degrees.  Yes, more ground clutter, but more offshore range.

Let's compare the radar imagery at .15, .5, and 1.5 degree elevation angles this morning (7:02 AM).  First .15 degrees....lots of sea clutter, but you can see the shallow convective showers way offshore.



.5 degrees--the range pulls in a bit.

1.5 degrees:  no sea clutter, but the horizontal range is much less.

With taller targets, the .15 degree elevation angle can see 300 km offshore or more.

This radar image also shows weak convective showers over the ocean in the cold, unstable air and substantial enhancement of the precipitation as the air is forced to rise by Olympics and coastal mountains.

Finally, the winds.   The vigorous cold front and the strong northwesterlies than followed produced some strong winds over the region--but nothing truly damaging or exciting.  Here are the max winds (mph)during the past 24 hr.  Gusts above 50 mph in and downwind of the Strait and some 40s over the Sound.  Notice how quickly the winds weakened over land.


 And yes, snow.  This kind of cool, unstable, northwest flow pattern is great for snow:  expect snow totals of 1-2 feet above 3500 feet.  The mountains needed some fresh snow.   Skiers will be happy.

Reminder:  if any of you want to attend the Northwest Weather Workshop on March 1-2 (next weekend) in Seattle, you can get more information and register here.

Inauguration -- today's near-miss, and some history

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Today's inauguration ceremonies for President Obama will take place under fairly nice conditions for this time of year.

Temperatures reached 60 degrees Sunday in Washington, and although it'll be quite a bit cooler today, the weather still will be better than what you'd expect in the nation's capital for Jan. 21.

If the ceremony were taking place eight hours later, or 24 hours later, it would be a lot different -- and not nearly so nice.

And in looking at history, you get even more appreciation for today's mild conditions. Some past U.S. Presidents have been inaugurated in horrible conditions.

For the official swearing-in ceremony at noon today, the forecast is for partly sunny skies and temperatures in the mid 40s. The average high for Jan. 21 in Washington is 43 degrees, and the temperatures might reach the upper 40s during Monday afternoon's inaugural parade.

A strong cold front, accompanied by a weak low pressure system, will cross the Mid-Atlantic later Monday. Snow could break out by late afternoon, temperatures definitely will be tumbling. All this will be accompanied by a stiff northwest breeze.  It's possible that an inch of snow could accumulate this evening.

Tuesday's high temperatures in Washington won't get out of the 20s, so it's a good thing the calendar has placed the inauguration today.

But as I said earlier, it could be worse.

The National Weather Service's office in Baltimore-Washington has produced a nice feature article, complete with photos, on the history of weather for the inauguration.

Anyone of my era probably remembers the inauguration of John F. Kennedy in 1961. The event already was historic, because Kennedy came into office as part of a new era in politics, as a fresh political face. He also came into office a day after an 8-inch snowstorm buried Washington.

Old video of the swearing-in ceremonies and subsequent parade make it look as if the inauguration took place in Duluth, not D.C.

Some other interesting tidbits from history ...

First, you'll remember that until Franklin D. Roosevelt's second inauguration in 1937, the event took place March 4.  In 1909, William Howard Taft's events were moved indoors because of an early-March snowstorm, with 10 inches of the white stuff. Winds knocked down trees and power poles.

A cold rain fell in 1841, when William Henry Harrison was sworn in. He caught pneumonia and died a month later.

In 1937, for the first Jan. 20 inauguration, a nor'easter moved up the East Coast. Temperatures were in the mid 30s, and more than 1 3/4 inches of rain fell in Washington. FDR insisted on riding in the inaugural parade in an open car.

Ronald Reagan's two inaugurations made history -- in different ways. In 1981, it was 55 degrees when he took the oath of office at noon. That's the warmest ever for a Jan. 20-21 inauguration.

But four years later, at his second inaugural, the parade was canceled in the wake of the worst arctic outbreak in the eastern United States in decades.  That was the outbreak that produced a low temperature of minus-5 degrees in Charlotte.  It was 7 degrees at noon that day in Washington, with wind chills of 20 to 25 degrees below zero.

Check out the Weather Service's article here http://www.erh.noaa.gov/lwx/Historic_Events/Inauguration/Inauguration.html

Farmers' Almanac not shutting down

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We interrupt coverage of Friday's potential winter storm system with some really important news.

The editor of the Farmers' Almanac said Wednesday morning that the annual publication, which is 196 years old, will continue to be printed.

That was in some doubt after an announcement earlier this week that the manufacturing facilities at the almanac's headquarters in Lewiston, Maine, will be shutting down. That closure will eliminate about 75 jobs.

Peter Geiger, the Farmers' Almanac editor, says the issues that have been printed at the Maine plant since 1955 had been used for promotional purposes. Geiger, the parent company of the Farmers' Almanac, produced a variety of promotional materials at the plant, Peter Geiger said.

But the Farmers' Almanac that you see on shelves in grocery stores, magazine racks and book stores was printed at another plant, in Wisconsin.

The Farmers' Almanac remains interesting reading. It is loaded with facts -- some obscure, some of real-life value.  It also contains a number of other articles, but its noteworthy appeal is meteorology.

The almanac, of course, contains weather forecasts that are produced far in advance -- more than a year in advance, for some months. The authors say their predictions are based on a number of scientific principles, and considering the inconsistencies of computer models used by the National Weather Service and other meteorologists, it's sometimes tough to criticize the Farmers' Almanac methods.

Geiger says the almanac is "much more than just a physical product. It's a way of life, a belief that you can live life more simply, naturally, and in harmony with the world around you."

By the way, the almanac's forecast for the next few days in Charlotte is "mild with showers."  Oh, well ... you can't get them all right.