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Snowsqualls and Other Joys


In January, Phil Chadwick read Dr. Richard Withington's "A Winter Islander" story and offered to write about the weather!  Phil knows weather.  In fact he is a senior member of the Canadian Government's Environment Canada. He graduated from Queen's University as a nuclear physicist and “Phil the Forecaster" has been a professional meteorologist since 1976.  We asked Phil to explain two important weather conditions that truly affect Thousand Islands winter living: Ice storms and the Lake Ontario snow belt.

Snowsqualls

I am a “weatherman” – actually a meteorologist and I have heard most of the jokes - and still enjoy them after 33 years. I am employed by Environment Canada as a severe weather meteorologist and you have probably heard some of the severe weather warnings I have issued for the Thousand Islands.

Snowsqualls are arguably the most important weather producer around the Great Lakes in the winter. In simple terms: never drive into a snowsquall if you can avoid it!  However, for those of you who must head to the Thousand Islands on Interstate 81, this is what often happens.

 

Cold Arctic air surging over the warm waters of the Great Lakes pick up heat and moisture to create conveyor belts of snow.

 

These snow conveyor belts are narrow bands of very unstable cumulus and towering cumulus clouds separated from one another by bands of relatively fair weather. Driving along Interstate 81 perpendicular to these bands, one drives through whiteout conditions with heavy, drifting and blowing snow into swaths of blue skies.  Travel is treacherous in the squalls where one can barely see the hood of your car. Lightning and thunder can accompany these snowsqualls especially those where the cloud tops reach up to 15 thousand feet or higher. These taller and more vigourous towering cumulus can create snow pellets and graupel which are thought to be requirements for the lightning process. Once lightning occurs, the towering cumulus graduate into cumulonimbus.

The snow with these Arctic outbreaks tends to have a low liquid to snow ratio as the flakes are formed in cold temperatures. The fluffy snow might only produce 1 part of water for 20 parts of snow when melted down. This low liquid to snow ratio is more than made up for by volume. Snowsqualls are directed onshore by the Arctic winds. If the winds do not shift, one area can receive the full deposit of snow from the conveyor. However, the winds can meander around distributing the same snow load to a broader area. Every case is unique.

The first snowsqualls of the season tend to be the most intense as the Great Lakes are still warm from a summer’s heating and fresh Arctic air sometimes makes southward surges early in winter. All of the Great Lakes get into the snowsquall game. The most active lakes have long axes parallel to the flow of Arctic winds. For Lake Ontario this means westerly winds and a snowsquall directed at Pulaski. If the land climbs rapidly from the lake shore, the snow is really squeezed from the snowsquall conveyor belt so that local terrain has a huge influence on just where the heaviest snow will fall.

The accompanying satellite and radar images are from December 8th, 2008.  This classic early season snowsquall event illustrates the main points mentioned. The long squall off Lake Ontario comes onshore all around Pulaski. The satellite image shows the entire snowsquall from space. There are also a lot of bright colours on the weather radar. (Typically bright means bad but I tell my Brother Jim to always consult an expert when looking at radar…)

Radar-Dec8-2008  Radar-Dec8-2008-StLawrence
The radar also shows how snowsqualls from Lake Huron and Georgian Bay can reach the north shore of the St Lawrence. Snowsqualls weaken with distance from their energy and moisture source so these squalls reaching Brockville are not too serious – just another beautiful day in the Thousand Islands.  The snowsquall is actually a continuous swath but the radar beam bends above the snow north of Lake Ontario so that radar can't see the entire snowsquall like the satellite can.

If the cold Arctic winds should shift to the southwest - 250 degrees to be precise, the snowsqualls come onshore between Kingston and Gananoque thus sparing Pulaski and Interstate 81 while closing down the 401.

Winter weather and snowsqualls are important! Drive safe and plan your activities around the weather.

And Other Joys - Freezing Rain

I worked throughout the last memorable freezing rain.  Do you remember the "Ice Storm of 1998". The warnings went out early and I didn’t get home for a couple of days. My own brother in Merrickville, Ontario, didn’t believe the forecast that 5 centimetres (2 inches) or more of ice, would accumulate on surfaces. Any amount of ice on roads is serious but 5 centimetres adding weight to structures is beyond the design of almost everything. No forecast could have prevented the freezing rain from happening but many might have saved themselves some anguish if they had bought backup supplies and a generator.

In Ontario, the St Lawrence and Ottawa Valleys are a focus for freezing precipitation – especially in mid and late winter. Low pressure areas approaching from the southwest collide with a cold Arctic outflow from a high pressure area parked over Quebec.

This combination as depicted is typically responsible for “passing” bouts of freezing rain across the rest of southern Ontario but several hours of freezing rain over the St Lawrence and Ottawa Valleys. Cold Arctic air funneling down the St Lawrence River or trapped in the Ottawa Valley typically extends the freezing rain from the hour or less experienced elsewhere to several hours.

The extreme occurrences of eastern Ontario freezing rain occurs when the upper jet stream flow is “split”. The northern branch of the jet stream continues eastward across northern Ontario and Quebec supporting the cold Arctic high. A southern branch of the jet stream completes a big loop around a nearly stationary low pressure area parked southwest of Ontario. The associated front is also nearly stationary sprawled along the lower great lakes. This combination occurs infrequently, but when it does, freezing rain can last many hours if not days in eastern Ontario.

There are two essential components to a freezing rain event. A strong flow of moisture typically from the Gulf of Mexico is turned into snow in the upper levels of the atmosphere and the storm. This snow falls into an above freezing layer of atmosphere aloft. The warm air melts the snow into rain drops completing the first main prerequisite for freezing rain. The cold northeasterly Arctic outflow from the high pressure area provides the freezing temperatures to supercool the rain drops below freezing.

At temperatures between zero and around minus 5 Celsius, the small particles in the air that ice crystals prefer to form on, are not “switched on” to making ice crystals and snow flakes. The rain drops cool below freezing but do not readily turn into ice. If the depth of the below freezing air is sufficiently thick and/or the air is colder than minus 5 Celsius, the rain drops will freeze into ice and are appropriately called ice pellets. Otherwise, the results are drops of supercooled water that freeze almost instantly on impact with a surface. The glaze of frozen rain is treacherous on roads in even the slightest accumulation.

Extended periods of freezing rain require a delicate balance between the two main components. The heat energy required to melt the snow flakes into rain in the warm layer aloft must be replaced by the warm southerly flow. Simultaneously the cooling energy required to supercool the rain drops in the below freezing layer adjacent to the surface must be constantly replaced by the Arctic outflow. Without the cold Arctic outflow, the freezing rain will change over to rain. Without the warm southerly flow aloft, the above freezing layer aloft is gradually cooled and the snow never melts into rain and the snow reaches the ground unmelted – as snow.

If these components are in a dangerous balance in the atmosphere as they were in 1998, the freezing rain can persist for long periods of time causing impacts that have huge societal impacts and are more severe than any tornado that I have forecast.

For those living along both sides of the the St Lawrence River, a winter forecast of rain or freezing rain must be taken seriously. If your surface winds should back (turn counterclockwise from east to northeast), the cold Arctic air is resupplying the cold layer at the surface. If your winds should veer more to the southeast, the cold outflow is weakening and the freezing rain is apt to change to rain. The wind is strongly funneled along the St Lawrence so freezing rain can continue with the cold northeasterly wind even after it has ended further inland. The northeasterly winds will continue until the low pressure area has shifted to the east of your location so be prepared for more than your share of freezing rain.

Freezing rain storms like this have happened in the past and they will happen again. The trees and forests are still recovering, now, more than a decade after the last big ice storm.

By "Phil the Forecaster" Chadwick
http://PhiltheForecaster.com

COMET Liaison Meteorologist,
Boulder, Colorado : Downsview, Ontario

Phil the forecaster, is well known as a meteorologist, but he is also an accomplished artist. "Weather and Art" - I combine my two passions and do presentations about the weather that can be deduced in famous Canadian art. I call this 'CSI' - Creative Scene Investigation. I am doing a presentation in February 3rd at the Museum in Brockville called 'Tom Thomson was a Weatherman'. He was and I can prove it."

 

His artworks are depictions of personal experiences. They hang in many private and corporate collections. (One of these is Gallery Streetsville in Mississauga, Ontario). Several magazines and calendars have used his work. Phil is also an occasional writer for Harrowsmith and other nature oriented magazines. Weather stories and art, both from a impressionistic but realistic perspective, get into print as often as possible!  He has just completed a book: The Weather of Ontario, which is scheduled for print in 2009.

Posted in: Nature
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Susie Smith
Comment by: Susie Smith
Left at: 8:28 AM Sunday, February 15, 2009
Jan Brabant wrote to TI Life today saying: "Thanks to Snow Squalls we have some of the best Snow Kiting In the East up on the Tug Hill just south of Clayton." Jan sent some photographs but we can't post them in our comment section. I suggest you link to Jan's T.I. Adventures website to see them and do continue to enjoy the snow and other joys!
Susan W. Smith
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