Transcript Notes/Science 10/May/May 7th, 2012

Science 10
Mr. Jean
May 7th, 2012
The plan:
• Video clip of the day
• Predicting the perfect snow day
– Types of storms
– Timing
– Public Opinion
• Powerful Planet – Atmosphere
– (Last 30 minutes)
Types of storms:
•
•
•
•
Nor’Easter
The Blizzard
Alberta Clipper
The Snow day.
The Nor’easter
What is a Nor’easter?
• Nor'easter (also northeaster; see below)
is a type of macro-scale storm along the
East Coast of the United States and
Atlantic Canada, so named because the
storm travels to the northeast from the
south and the winds come from the
northeast.
• The storm has characteristics very similar
to a hurricane.
• Most nor'easters start
from a low-pressure
system that forms in the
south, most often the Gulf
of Mexico, and are drawn
across to the Northeast
by the Jet Stream.
– Tracks Northeast and
heads up along East Coast
past the mid-Atlantic and
New England coastal
states.
• The counterclockwise flow
around a low-pressure
system brings the warm
moist oceanic air over
land. The warm moist air
meets cold air carried
southward by the trough.
– The low enhances the
surrounding pressure
gradient, which acts to
spiral the very different air
masses toward each other
at an even faster rate.
– The greater the
temperature differences
between the two air masses
the greater the turbulence
and instability, and the
more severe the storm can
become.
Conditions most favourable for a
snow day.
• Nor’Easter
– Significantly cold temperature.
– High wind speeds
– Start time around midnight
– Continues into the day without decreasing in
intensity until mid-day.
– Probability: 75-90% for a snow day.
The Blizzard:
• A blizzard is a
severe snowstorm
characterized by
strong winds.
The Blizzard:
• By definition, the difference between blizzard
and a snowstorm is the strength of the wind.
• To be a blizzard, a snow storm must have
sustained winds gusts that are greater than or
equal to 56 km/h with blowing or drifting snow
which reduces visibility to 400 meters or less
• Must last for a prolonged period of time —
typically three hours or more
The Blizzard:
• Blizzards can bring near-whiteout
conditions, and can paralyze regions for
days at a time.
• A significant range of snowfall can occur.
Generally a typical East Coast Blizzard will
have 20-45cm of snow associated with it.
Conditions most favourable for a
snow day.
• Blizzard:
– Significantly cold temperature.
– Occurrence during commute
– Significant snow fall associated with Blizzard.
– Probability: 90-95% for a snow day.
Iran Blizzard of 1972
• The Iran Blizzard of February 1972 resulted in
the deaths of approximately 4,000 people. A
week-long period of low temperatures and winter
storms, lasting from February 3 to February 9,
1972, dumped more than ten feet of snow
across rural areas in northwestern, central and
southern Iran.
• Southern Iran sustained as much as 26 feet of
snow, burying at least 4,000 villagers.
The Alberta Clipper
The Alberta Clipper:
• An Alberta clipper is a fast moving low
pressure area which generally affects the central
and Atlantic provinces of Canada and parts of
the Upper Midwest, Great Lakes and east coast
regions of the United States.
• Most clippers occur between December and
February, but can also occur occasionally in the
month of November.
How it’s formed:
• Originates when warm, moist winds from the
Pacific Ocean come into contact with the
mountains in the provinces of British Columbia
and then Alberta.
• Travels off of the mountains, then develops into
a storm over the Canadian prairies when it
becomes entangled with the cold air mass that
normally occupies the region in winter.
• The storm then slides southward and gets
caught up in the jet stream, sending the storm
barrelling into central and eastern areas of North
America.
Properties of an Alberta Clipper:
• The clippers, when reaching the Atlantic
seaboard can cause a weather 'bomb' by
trapping the Atlantic coast’s moisture close
to shore.
• This results in larger snowfall amounts
which can approach 6"-12" or more.
Conditions most favourable for a
snow day.
• Alberta Clipper:
– Storm must begin between 10pm and 2am.
– Weather “Bomb” must develop to ensure large
snowfall.
– With temperature below zero this storm
pattern can cause a snow day.
– Strong winds.
– Only a 50 to 80% probability of snow day if
those conditions are met.
Big Time Snow!
Links to snowfall:
• http://www.thegreenchildren.org/tgcf/found
ationpress/tag/snow/
BBC – The Atmosphere