December
looms on the late November horizon, leaving us wondering how it will treat us
this year. Will it be cruel or will it be kind? It has been both in recent
years.
Last
December was a brute. It was slightly warmer than average but it snowed 27 of
31 days in Haliburton County. Snowfall totalled 134 centimetres, more than
twice the average for December.
The
year before that - 2015 - was extremely kind. It snowed on only 12 of the 31
December days, and measurable snow was recorded on the ground on only seven
days because average temperatures were well above normal.
There
is some evidence that this December will not be so gentle.
Expect "a wild ride from start to
finish,” the Weather Network said in its Canadian winter forecast released
this week. There will be changeable weather patterns featuring extended periods
of “high impact weather.”
“High impact weather” is not defined but I
translate it to mean rain and freezing rain one week, monster snowfalls the
next, then a couple of days of bone shattering cold. A truly genuine mix of
miserable winter weather.
Ontario, says The Weather Network, can expect
above average snowfall and near normal temperatures.
That
forecast follows early predictions by the Canadian Farmer’s Almanac. It
predicts much ice, cold and snow for Ontario this winter. Snowfall will be
above normal and cold below normal with some places going as low as minus 40
Celsius.
The
Almanac says it has 80 to 85 per cent accuracy in its forecasts, except in El
Nino years of which 2018 is not one.
Environment
Canada, which hedges its bets in statistical gobbledygook and scientific
language, appears to be forecasting colder than average temperatures and above
average snowfall.
Generally,
this year’s winter forecasts have been hedged and as varied as a pot luck
dinner menu. The reason is that forecasters are uncertain how water
temperatures on the Great Lakes will affect Ontario’s winter.
Lake
Huron temperatures were below average during an unusually wet and cool summer. That
changed quickly, however, with a sunny, warm autumn. Lake Huron’s surface
temperature was close to 22 Celsius in late October and has remained above
normal.
Warm
surface water on Lake Huron can bring lake-effect snow to Muskoka and
Haliburton. Cold, dry air picks up heat and moisture when it passes over the
warm lake surface, creating bands of lake-effect snow.
The
warmer the water and the colder the air, the more intense the lake-effect snow
bands become.
December
is an ideal month for lake-effect snow storms because the lake surface is still
warm relative to the colder air passing over them. Extremely cold weather
freezes the water, obscuring the moisture and heat and making it difficult for
lake-effect snow to develop.
Lake-effect
snow bands are long and narrow, averaging six kilometres in width and
stretching 50 to 400 kilometres in length.
Wind speed often determines how far a lake-effect
snow band stretches. Weak winds usually see the snow falling along Lake Huron’s
shorelines and into western Muskoka. Strong winds can bring it into Haliburton
County.
The good news is that when winds are exceptionally
strong they pass over the lake’s surface too quickly for snow bands to form.
No matter what the weather gives us this December,
one thing is certain: Lake-effect snowstorms are going to be an increasing
factor in our winter lives.
Annual average ice cover on the Great Lakes has
declined 71 per cent in the last 40 years, says the Great Lakes Integrated
Sciences and Assessments Centre (GLISA) based in Michigan. Total annual
precipitation increased in the Great Lakes region by 11 per cent during the
same period.
The centre also says average temperatures in the
Great Lakes region have increased two degrees Fahrenheit (1.1C) since 1900.
For anyone who wants to compare this December’s
weather as it moves along, here are some statistical averages:
The average high December for Haliburton County is
minus 1.5 Celsius. The average low minus 12.5C. The record high for December was
14.5 C recorded on Dec. 5, 2001. The record low was minus 38.5 recorded
December 27, 1993. The average December snowfall is 59 centimetres.
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