Download The Frontenac Arch Biosphere, Near perfect Weather and Climate?

The Frontenac Arch Biosphere
Near perfect Weather and Climate?
By Phil Chadwick January 2012
Some believe that if you schedule holidays at the same time as the local meteorologist,
you are bound to have good weather. You can carry that a bit further to even influence
where you decide to live. The Frontenac Arch Biosphere (FAB) may be nearly perfect
and I will explain why.
The FAB doesn’t make it into the climatic record books of Canada. You might think that
it is bad thing not to hold weather records. Actually the reverse is true. The FAB
doesn’t get too hot, too cold, too wet, too dry or too stormy. To quote Goldilocks, the
weather and climate in the FAB is just about right. Remember that weather is what you
get while climate is what you expect. There will always be exceptions with any
generalization.
Here are some meteorological reasons to live and
play in the Frontenac Arch Biosphere.
Freezing rain frequency – much higher along the Ottawa River and the lower St
Lawrence River east of Gananoque.
Dangerous freezing rain episodes is actually lower in the FAB. The cold air at the
surface that is required for prolonged periods of freezing rain tends to get trapped in the
valleys of the Ottawa River and the lower St Lawrence River east of Gananoque. The
most dangerous freezing rain cases rely on a large, cold Arctic high parked over central
Quebec. This high directs cold and dry Arctic air across eastern Ontario.
The heavy, frigid air is tough to move and the air in the valleys is continually reinforced
with fresh cold air funneling up the river valleys. This frigid Arctic air in the valleys will be
the last to be dislodged. The cold air is quickly flushed from the terrain of the Frontenac
Arch Biosphere especially over southern sections along the St Lawrence west of
Gananoque. The exceptions are in the most extreme cold outflow cases like that of
January 1998 although areas north and especially east of the FAB still received much
more ice. The precipitation changes to rain when the cold air retreats to the east. As a
result the frequency and duration of freezing rain events in the FAB is about half that of
Ottawa, Perhaps the nation’s capital should be moved to Lyndhurst?
Snow squall frequency – nil off Georgian Bay and Lake Huron. Only with a 230
degree wind off Lake Ontario.
The FAB is almost immune to snow squall events which cause very dangerous
travelling conditions mainly due to extreme snow accumulations and near zero visibility
in whiteouts. The risk of snow squalls in the FAB is highest in the south and gradually
diminishes to the north.
Cold air blowing over the warm and open waters of the Great Lakes is the simplest
description of snow squall generation. The actual science is a lot more complicated to
explain the details of these severe weather systems but way beyond that which is
required to further explain why the FAB is a great place to live. Generally the cold Arctic
winds are those blowing from the north through to the west. With westerly winds, the
FAB is only downwind from Lake Huron and Georgian Bay. A lot of varied terrain and
300 km separates the FAB from the source of these westerly snow squalls. By the time
the westerly snow squalls reach the region they are so torn about by terrain that they
pose nil threat to either a significant snow accumulation or a reduction in visibility.
Disorganized flurries and light accumulations are all that the FAB can expect.
Less frequently cold Arctic air can come from the southwest across Lake Ontario
towards the FAB. Cold Arctic air approaching from the southwest can happen but it si
rare. A wind blowing from 250 degrees will direct these snow squalls down the St
Lawrence River Valley and touch the southern portions of the FAB. A 240 degree wind
will direct these squalls onshore near Kingston and a bit further north into the FAB. A
220 degree wind will take these squalls further north still. Once the winds back to 200
degrees there is no longer enough fetch across Lake Ontario to generate much a snow
squall so light flurries is the worst thing that can happen over the FAB. Once again the
further these squalls move from their source region, the weaker and more disorganized
they become.
Heavy Snowfalls and the FAB
The FAB is subject to heavy snows associated with Colorado type lows headed
northeastward from the Mississippi Valley. These systems can affect all of southern
Ontario. The exact path of these systems is critical and can change the weather that
actually arrives with them drastically. The following graphic gives the weather
associated with different areas of a typical Colorado low over southern Ontario.
The following graphic shows that over the long term the FAB gets .5 days per years with
a big snowfall exceeding 25 cm. Another way to look at this is that the FAB might get a
big snowfall once every couple of years on average.
The following graphic depicts mean annual precipitation and the snowbelt areas.
The data confirms the orientation of the snow squalls over the southern portion of the
FAB. It also reveals a general decrease in annual precipitation from the south to the
north. Once again the climate in the FAB is almost perfect - neither too wet or too dry.
Severe Convection
In Ontario the probability of thunderstorms decreases from the south to the north. The
average annual lightning map displays this dramatically. In the FAB the probability of
lightning is much less than that experienced in southwestern Ontario but there is almost
no north to south decrease in lightning. This is a result of Lake Ontario. In summer the
comparatively cool waters of Lake Ontario create chilly onshore breezes that collide
with the prevailing winds. This collision of winds sets up lines of convergence which
help to steer thunderstorms. In eastern Ontario these convergence lines run close to or
just south of Highway 7. The orientation of these lines of enhanced thunderstorm
activity can be seen in the lightning map. As a result there is no south to north
decrease in lightning activity in the FAB.
However the convection that follow this Lake Ontario convergence line has a higher
probability of reaching severe limits. These dangerous storms typically follow the
Highway 7 corridor toward Ottawa. The most severe storms tend to steer to the right as
they move. These “supercell” type thunderstorms are severe and explain why even the
FAB sometimes receive damaging thunderstorms. Thankfully, the right moving
supercell thunderstorms that can tear right along the Frontenac Arch are an infrequent
and rare type of thunderstorm. These supercell thunderstorms are responsible for the
more damaging tornadoes. The accompanying figure illustrates that the probability of
F1 or stronger tornadoes is minimal along the St Lawrence portion of the FAB but
increase toward Highway 7. Now you know why.
The FAB is not too cold. The following graphic illustrates the moderating warming
influence of Lake Ontario and the St Lawrence River on the FAB. This moderating
warming effect diminishes to the north but only slightly due to the weaker but still
significant moderating effects of the Rideau River and canal system.
The FAB is not too hot. The following graphic illustrates the moderating cooling
influence of Lake Ontario and the St Lawrence River on the FAB. This cooling
moderating effect diminishes remarkably to the north. The moderating effects of the
Rideau River and canal system to keep the temperatures lower are not nearly as
significant during the warm seasons. Ottawa gets almost as many hot days as Toronto.
The FAB is not too windy. The following map reveals that the strongest wind gusts are
typically along the shores of the Great Lakes or in areas of exposed, flat terrain. The
rugged Canadian Shield of the FAB tends to keep the wind gusts lower.
The FAB is not too foggy. Fog is not typically an issue – possibly because the arch is
that much more removed from the pollution of southwestern Ontario and the
neighbouring United States. Fog may all look the same to the casual observer but it
comes in many different flavours from different causes and effects. Advection…
radiational… precipitation… Arctic sea smoke. Fog is not a big issue in the FAB.
And then there is the landscape… from the Thousand Islands to the inland lakes
connecting to the Rideau waterway. There is everything from the big water of the St
Lawrence to the quiet of the back ponds. All of these scenes are accessible by trail and
canoe. One just needs the time…
About Phil Chadwick
Trained as a nuclear physicist, Phil found a career in meteorology with Environment
Canada in 1976. Phil specializes in severe weather conditions and has been the
meteorologist behind the "scenes" in some very major weather stories. Currently Phil is
training meteorologists and completing some research work.
Phil is an occasional writer for Harrowsmith and other nature oriented magazines.
Weather stories and art, both from a realistic perspective, get into print as often as
possible! Phil also does presentations on a wide range of topics from the weather to
art, climate change and land stewardship.
Phil is also interested in the birds and the bees. As a beekeeper (apiarist), he keeps up
to 10 colonies on the family farm.
Phil's artworks are depictions of personal experiences. They hang in many private and
corporate collections around the globe. Several magazines and calendars have used
his work.
http://philtheforecaster.blogspot.com
Sources: The “Weather of Ontario” book published by Lone Pine Publishing by Phil
Chadwick and Bill Hume. All maps are from Environment Canada