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Story from the Seattle Times from January 28th, 1991
Titled "A Storm To Remember"
Memories of the Dec. 18th snowstorm are still vivid for most of us- spinning wheelsand bashed fenders, traffic gridlock and abandoned cars, bone-chilling cold.
Well, Seattle's weather forecasters also have unhappy memories. Most of Seattle's snowstorms are erratic and hard to predict. But Dec. 18th was in a class by itself and finally turned into a three-part nightmare. You'll recall the snow was expectedto be riding a push of cold arctic air from Canada. But snow began falling that morning in Seattle's north end before the arctic front had even crossed the U.S.-Canada boarder. At 2PM with the front barely at Bellingham, the snow began falling heavily between Boeing Field, in Seattle's south end, and Everett.
And finally at 6PM as expected, the arctic front pushed past Seattle, dropping a few more inches of snow. But by that time, the damage had been done. The city and areas north and east were smothered with as much as a foot of snow, and many of us were stuck far from home.
"If we could have forecast exactly when the snow was going to start, it would have spared thousands of people anguish that night" Said Brad Colman of the National Weather Service's Seattle forecast office.
Unlike most of us who are no more prepared for snow now then we were before Dec 18th, the weather service's Seattle office is developing a major program with the University of Washington to upgrade local forecasting with a special emphasis on snow. It's the nation's first such program between the weather service and the University.
"Snow is the most difficult forecasting problem" said Clifford Mass of the UW's atmospheric-sciences department. "We are doing something we never do otherwise, and that is forecasting the amount of precipitation.
"the rest of the year we forecast temperatures and the probability of rain, but we never try to tell you how many hundredths of and inch are going to fall."
Colman added "We try to hold off on estimating the amount of snow because we just don't have the skill. But as soon as snow is in the forecast, the phone begins to ring. How much? How much?"
Mass' students checked the records for snowstorms that behaved like the one on Dec 18th. They found only one in the past 40 years.
"Dec 18th was very unusual, "Mass Said. "The trouble is, a significant number of our snowstorms are very unusual. That's why we're putting so much effort into snow forecasting. "We realize it's the biggest problem we have right now."
Still, significant improvements in snow forecasting is probably years away, awaiting better monitoring equiptment and bigger computers.
The National Weather Service's forecasting center produces computer simulations of the hemisphere's weather, updated every six hours with information from satellites, weather balloons, ground stations, ships at sea and aircraft. But the weather service's main computers, among the fastest in the world, are loaded to capacity. Resolution- the smallest features the computer can see-is about 50 miles.
The computer can't see most thunderstorms. It doesn't even know about the Olympic Mountains, which often shield Seattle from ocean rainstorms but which can also set up a zone north of Seattle where converging winds can dump rain-or snow as happened early on Dec 18th.
And of course, discussions go on as to what happened on Dec 18th. Long-Range forecasts days before had seen the arctic front coming. The arrival of most such fronts produce 1-3" of snow. Then the skies clear and the temp drops. That what forecasters were expecting this time.
But snow began falling along the King-Snohomish co. line early that morning. It was the convergance zone at work. Westerly winds off the ocean were bing diverted by the Olympic mountains, some pushing though the Chehalis River Valley and then turning north over Puget Sound, and blowing through the strait of Juan de Fuca and turning South into the sound.
Were they converged between Seattle and Everett, the moist air pushed higher, cooled then produced snow. "Were were still expecting the arctic front in the evening. The snow farecast was timed for that"
But 4 miles above Seattle something was happening that was going to throw off the forecast, embarrass forecasters and cause a world of misery for working people who were hoping to get home before the snow began to fall.
An upper-level low pressure area moved over Seattle. The low pressure unloaded weight from a column of air above Seattle. Barometers at Stampede pass in the cascades, at Sea-Tac airport and at Forks near the coast all registered sharp drop in air pressure. In effect it created a "hole" that surrounding air rushed to fill in.
"Wind at Sea Tac jumped from SW 10 to SW 25 in just over an hour" Colman said. "The same thing was happening in the Strait"
The moist air rushing in from both directions colided over Seattle rose and began to produce snow.
" It was very difficult to predict, and it snowed like the dickens" Colman said.
Oh and looking at the TV guide section of the paper, this was the rundown for primetime.................
Unsolved mysterys
Major Dad
Cheers
A current affair
Bob Newhart
Murphy Brown
To say the least, winter had announced its return in a dramatic way!
