Snows of the Maritimes


Shunpiking, March, 1996 Volume One, Number Two


Quick scroll on this page to...
snow flake '...Generation level...'
snow flake '...the synoptic low-pressure system...'
snow flake '...winds out of the northwest, chance of flurries...'
snow flake '...mean total annual snowfall...'
snow flake ...Road Weather Information Systems...'
snow flake Snows of the Maritimes: Factoids

THINK ABOUT BEING in a snowstorm for a moment. It can bring warmth and coziness to winter holidays, but cold fear when unexpected. Although composed of water, it blankets our forests in a cold sheet. And though nothing seems "as pure as the driven snow", the white stuff effectively traps pollution within its crystals and ferries it to the ground.

snow flakesSnowfall statistics do not help resolve these mixed messages. Does Halifax really get more snow in more seasons than Tuktuyuktuk? Also, how can people label a snowfall "the storm of the century" when we have only been keeping snowfall records for forty years?

These mysteries, however, do not seem to be burdening too many Nova Scotians. Sure, many of us try to listen to the morning radio forecast, and when there is a real snowstorm, the television news never fails to beam the familiar images of driving snow, creeping, ditched and crashed cars, and stumbling pedestrians. Yet aside from the odd raging blizzard each winter, our daily routine is not that much disturbed by snow.

But how much is snow simply a part of us which we do not often contemplate; an invisible, integral part of our lives which we do not acknowledge? Some reflection and research -- focussed by a sore back earned from shovelling the drive -- have helped shunpiking discover that snow affects us more than we know it.

But first of all, why does it fall? I called Michael Pancura, an Environment Canada forecaster who has been making a living from snowfalls, and other weather systems, for almost twenty years. Almost immediately after my first question I realised I was in for some work. Terms like "vapour pressure differential", "colloidal suspension" and "synoptic low-pressure system" had me begging for translations. Mr. Pancura, at the risk of simplifying two decades of experience, provided them.

'...Generation level...'

No surprises here. Snow is born in clouds where cold and moisture combine to make ice crystals. What is surprising is that other particles, like dust aerosols, sea salt crystals, or volcanic and industrial ash, are usually needed to act as a nucleus to spark this formation. "The chemical property of that particle will determine whether it will freeze," Mr. Pancura explains.

Because of this piggyback effect, snow is thought to be a significant culprit in bringing pollution to the ground. Scientists in Scandinavia are going so far as to view snow as an acid reservoir; a white blanket that stores its industrial contents until the spring thaw. Then, ecosystems receive an unnatural shock as snowmelt releases their contents in an intensively short period.

A catalyst for ice crystals, whether clean or dirty, is not always needed. When the cold is extreme such as when the air in the cloud tops reaches -35 or -40 degrees Celsius, crystallisation can occur spontaneously.

Remember, we are still very much up in the clouds. Just because the crystal has been generated does not necessarily mean snow. The crystal must first build up a critical mass before falling out of the cloud. Even then, the descent will play a large role in defining the precipitation.

Freezing rain, sleet, ice pellets, or rain are all possible depending on what wind and air masses prey upon the lonely crystal. If it is to become snow, it must continue to encounter low temperatures and moisture, gaining substance as water vapour freezes directly to its surface. Snow crystals result. When these meet up with fellow crystals, they become what are known as snowflakes.

'...the synoptic low-pressure system...'

The above story describing snow creation differs little if you are in the Nova Scotian Cobequids or the Peruvian Andes. What does change is the way snow is brought to the ground. This process of snowfall distinguishes our winters from those of our neighbours. It also shapes many of our deepest feelings towards snow: it is storm that we fear -- not so much the foot and a half of snow left over. Likewise, it is the gentle flurries we enjoy -- not usually the slush the next morning.

SnowandrainThe identity of Nova Scotia's snows, in this sense, is closely tied to the most intriguing, and violent, of our winter storms: our low-pressure systems.

"Every storm that goes by Nova Scotia has a moisture signature," Mr Pancura explains as he begins to describe this system of snowfall. This signature, he goes on, plays a tremendous role in whether we get snow, sleet or rain. The warm currents from the Gulf Stream, the chilly waters coming down from Greenland, or the dry surface of New Brunswick all feed a storm very different temperatures and levels of moisture.

Coldest Days oC DATE LOCATION
Newfoundland & Labrador -51.1 Feb, 17, 1973 Esker 2
New Brunswick -47.2 Feb. 1, 1955 Sisson Dam
Nova Scotia -41.1 Jan. 31, 1920 Upper Stewiacke
Prince Edward Island -37.2 Jan. 26, 1884 Kilmahmaig

Source: Canadian Geographic, December, 1991

The swirling low-pressure storms carrying these sometimes moisture-rich clouds often have colourful names that describe their origins. "Hatteras Lows", for example, are born in the moist air off the coast of Cape Hatteras in the Carolinas, and follow a north-easterly track up the American east coast. "Alberta Clippers", as the name suggests, form over the cold and dry prairies and come roaring over Ontario, Quebec and New Brunswick before slamming into us.

The path these lurching swirls take, always spinning counter-clockwise on the TV satellite images and moving from the eastern American states or New Brunswick towards Newfoundland, is crucial in determining whether your neighbourhood will get rain -- or snow.

"If the track [of the storm centre] is west of us, most areas in Nova Scotia will have rain. If it is south of us, everyone -- usually everyone -- will get snow."

Have the mysteries of snowfall suddenly been solved? Can we turn the weather reporter's voice off and predict snowfall from the images? Unfortunately no: the complexities remain.

"It's not easy -- if it were easy we would never be wrong," Mr. Pancura emphasises, as he launches into a host of other variables which make low-pressure weather systems hard to predict.

Some generalisations do help. Take a case where the centre of one of these systems slides over the Gulf of St. Lawrence in December. Cape Bretoners had better have their snow tires on: the warm, heavy clouds that have scooped up moisture from the still ice-free Gulf waters are about to be driven across the cold highlands. They will be pushed up -- and have their watery contents frozen and unceremoniously dumped. Possibly, if the wind is driving so strongly that there is a white-out... the storm will become a blizzard.

Take another example, this time on the Atlantic side. If a "Hatteras Low" swings by off our coast we will all be more likely to get drenched in rain. Why the difference? The reason for our special treatment is simple: the swirling clouds in their push up the eastern coast of North America have picked up balmy Gulf Stream wetness. The counter-clockwise direction of the wind brings this wetness in from the Atlantic, across the flat country of southwest Nova Scotia. The topography required for a snowfall is missing -- the clouds stay low, remain relatively warm, and consequently rain.

'...winds out of the northwest, chance of flurries...'

Our winters can also bring snow without the low-pressure violence of storms.

Serene, gentle flurries, for example, are usually from a completely different family of storms than a low-pressure system. Here, the province might be described by "a cloud dome or uniform air mass." These can be huge: picture the area of Quebec and raise the ceiling ten miles high and you have a typical one. The boundaries of these cloud domes might be tormented as different masses of air collide, creating high and low pressure systems -- but within it there is consistency and stability in the weather.

Here precipitation is caused by some old reliable climatic features of the region. Winter northwesterly winds, for example, keep blowing as long as the planet keeps on turning. Although the violence of blizzards may be absent, the land's topography and air's moisture content are usually constant. the winds blowing air moistened by the Gulf of St. Lawrence up and over cold high country provides that ideal snowfall that is actually pleasant to be under.

So storms and "domes" provide two different vehicles for the same precipitation; yet another example of snow's many faces. And as any scientist will point out, this is a brief treatment. After all, storm physics includes high-altitude jet streams, upper-level troughs, anticyclones, up-drafts and mesoclimates. However, as this is a story on snow, and not just storms, it is time to ground the article on the question: when and where do they land in our province?

'...mean total annual snowfall...'

The Cobequid Mountains and the Cape Breton Highlands each regularly receives 10 to 14 feet of snow -- a depth that buries some houses -- each year: far and away the most in the province. These regions also own the heaviest seasonal snowfall records: Cheticamp and Copper Lake received well over 18 feet of snow in 1964-65 and 1971-72 respectively.

When defining the snowiest zones, however, scientists like to use more cautious 30-year averages. the reason is simple: extremes do not always tell a meaningful story. Rainy Yarmouth, for instance, received 69 cm on a single day in 1885. Yet Yarmouth County consistently gets less snow than higher elevations: usually only about four or five feet in a whole season.

One of the reasons for this is topography: Yarmouth, Shelburne and Queen's County are not known for their relief -- an important ingredient needed for snow. Relief drives moist air up into the cold heights of the sky. By doing just that, the Highlands and the Cobequids ensure heavy snowfalls because all the conditions for snow generation are present.

It is microclimates like these that can set up some surprising comparisons such as that of Tuktuyuktuk and "snowy" Halifax. While Tuktuyuktuk gets comparatively little snow, little of it melts away. Our perceptions of who gets the most snow is greatly influenced by this. These facts remind us that snow generation requires moisture, as much as it requires Arctic-like temperatures.

These differences exist within Nova Scotia too. Why do some Nova Scotian communities consistently get 10 feet more than others?

The northern shore of Nova Scotia, for example, is subject to the effect of the annual freezing of the shallow Northumberland Strait. This denies the moisture necessary for plentiful snowfall as well as the moderating temperature influences water bodies give to the rest of Nova Scotia.

These variations in temperature, while welcome breaks from the chilly weather experienced elsewhere on the continent, also wreak havoc. Combined with snow, driving conditions can become deadly. Our roads, bridges, and structures expand, shrink and crumble. And it seems we have no choice but to respond with absurdly expensive measures to deal with these nuisances.

...Road Weather Information Systems...'


Our example illustrates this problem. A provincial report has estimated that Nova Scotian highways, due to fluctuating temperatures and frequent storms, receive an average of 20 tonnes of salt each kilometre. Unfortunately for the roadside homeowners who rely on well-water, road safety remains the priority and will so as long as we are a society dependent on motorised wheels.

This dilemma also demonstrates why the study surrounding snow's complex signals is serious business. And while we are not vulnerable to avalanches as they are in western North America, east coast snowstorms can be just as tragic. Witness the greatest ocean tragedy in Canadian history -- the capsize of the Ocean Ranger oil rig in February 1982 which killed 84 people. A snowstorm was involved, along with corporate negligence. The dreaded "bomb" to be precise: a low-pressure system which deepens dramatically over the span of 12 hours.

snowmapWhen storms kill mariners, disrupt fisheries, slow down commerce, and isolate our car-dependent communities they reveal the crucial importance not only of forecasting, but also our reactions to the forecast. How do we prepare for storms? Which roads are salted? How many rescue helicopters are on stand-by?

These questions are relevant from the household level to the Coast Guard. What emerges from them is perennial. The salt, shovel, and emergency candle are as cultural to us as they are practical. We are bred with these pillars of snow safety all around us. Winter weather is part of our politics too: political columnist Don Braid once described Canada as "the confederation of crummy climates."

Despite the indivisible connections between our weather and our culture, however, snow still retains many sides which we ignore. It would help us all if we understood more about the forces that deliver snowflakes to our home. We live in communities which can have very diverse microclimates and snow patterns. Naturally we react to snowfalls in our individual ways because of that. Self-examining how snow shapes our winter routines is useful to understanding what sets us apart from our neighbours -- whether they are down the coast a few miles, or across the continent.

Clearly, there is something very personal about exploring our experience with snow. The complex meteorology might elude us, but our joyful -- and distressful -- reactions to the white stuff are clear, immediate and inevitable. They remind us that the many faces of snow do not merely shape our day -- they help make us who we are. Think about that the next time you are in a snowstorm.

Snows of the Maritimes: Factoids

Moncton -- "one Doug high"

And what about that snow magnet called Moncton at the head of the Bay of Fundy? In 1991, a single storm dumped 163 cm on what happens to be the snowiest town in the maritimes. Doug Mercer, a PhD student at Dalhousie University with the Atmospheric Science Group remembers it well; the amount of snow matched his height exactly, prompting his friends to describe the depth as "one Doug high."

St. John's... and Paris

Newfoundland is subject to more extremes than the Maritimes. Perched on the continent's eastern tip, St. John's sits at the intersection of immense weather-generating systems, and is home to a fascinating array of weather. Its variability and moist, temperate salt air are what you would expect from a marine climate, but it is not entirely marine. Air masses from eastern North America sweep over the city, bringing contrasts in weather.

Despite their ferocious reputation, winters are comparatively mild. Its average temperature enables it to boast, with Victoria and Vancouver, one of the mildest winters and the greatest variety of trees and shrubs anywhere in Canada. Two or three times a year, an Atlantic storm dumps an enormous snowfall and buffets St. John's with strong winds. January-February 1987 were the snowiest winters in recent memory, made worse by the scant thawing between snowstorms. In total, more than twice as much snow fell as
normal -- almost eight feet. In general, though, nature aids by melting the snow. Freezing rain, known locally as "silver thaw", is another major weather hazard of winter and early spring. St. John's is at the same latitude as Paris ... if only in the springtime. (source: Canadian Geographic, July/August 1992)

Cost-benefit

$80 million is spent every season in Nova Scotia on snow removal. Despite that, insurance companies pay out between $300-$400 million from weather-related automobile accidents each year. How much do we pay to the insurance companies? Although that figure includes fog and rain-related incidents, it remains a testimony to the expense, and danger, of snow on our roads.

Snow industry

Aside from meteorologists, it involves hydrologists, geographers and climatologists delving into problems of chemistry, statistics and mapping. The reason for the concern is simple. Accurate snow knowledge saves dollars, helps protect our environment and is crucial to saving lives. Snow is also the backbone of a recreational industry supported by skiers, snowboarders, sledders, etc.

Politics and natural disaster

The threat of winter disaster fuels political fights every season. Issues as varied as EH-101 helicopters (useful for winter rescue operations) and the diversion of highway funds from improving Wentworth's "Death Valley" stretch of highway (so-called because of the danger posed for motorists during the winter) are both examples. Both debates connected to the public's safety in winter, and both involved millions of public dollars. Snow may also be somewhat ominous: in July 1949, the year Newfoundland joined
Confederation, it snowed.

Snow and Rain

Water that falls from a cloud is called "precipitation" and may take the form of rain, drizzle, hail, sleet or snow. Whether it falls as one or the other, depends on conditions inside the cloud and the temperature of the air outside it. The height at which water freezes as it condenses out of a cloud is called the "freezing level." The ice crystals grow rapidly into snowflakes as water droplets freeze onto them. If the freezing level is below 1,000 ft., the ice crystals will not have time to melt before reaching the ground and will fall as snow.

If the base of a stratus cloud is low enough, small droplets of rain may fall as a fine drizzle. Dry snow may fall as a afine drizzle. Dry snow falls when the ground temperature is cold, but if snow falls from a cloud into air that is just above freezing, some of it will melt. The resulting mixture of snow and rain is called "sleet."


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Copyright New Media Services Inc. 2004. The views expressed herein are the writers' own and do not necessarily reflect those of shunpiking magazine or New Media Publications.