Transcript Regional Weather

Regional Weather
Thermals
• Thermals are a rising current of warm air
caused by convection – it is also known as
an updraft.
• The sun heats up the land and the air just
above the land heats up and rises. This
rising, warm air is our thermal.
• Balloonists and gliders depend on thermals
to help give them lift.
Sea Breezes
• Wind can be caused by the land near a
large body of water heating up and creating
thermals.
• The air over the land rises and when it rises,
the air over the water moves in to take its
place.
• The air in the thermals cools and drops
down to take the place of the air that moved
in from over the water.
Sea Breeze Formation
Land Breezes
• Land breezes are the reverse of sea
breezes. They occur later in the day as the
temperature is dropping.
• The land cools much quicker than the water
(which stays warmer longer).
• The air above the warmer water rises as
thermals and is replaced by cool land air.
• The warm air then cools and replaces the air
that was once over the land.
Land Breeze Formation
Lake-Effect Snow
• Lake-effect snow occurs during the winter when a
wind sweeps across a large body of water that has
retained some heat from the warmer weather
earlier in the year.
• The wind picks up some moisture from the lake
and carries it up over the land.
• The land is much colder than the lake so the
moisture cools and condenses and falls as
precipitation (snow).
• Much of the snowfall experienced by the Durham
Area is the result of Lake-effect snow.
Lake-Effect Snow Formation
Chinook Winds
• Chinook winds are seen in Western Canada
and are caused by the mountains and
“orographic lifting”.
• The orographic clouds form by moisture
condensing as it rises up the mountain. This
condensation releases heat that stays in the
air and travels down the other side of the
mountain and out over the prairies as a dry,
warm air mass.
Chinook Wind Formation
Precipitation & Humidity
Precipitation
• Precipitation is any water that reaches the
ground in either a liquid or solid form.
• The type of precipitation that falls depends on the
temperature on the ground and in the atmosphere.
• Types of precipitation may include…
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Drizzle
Rain
Freezing Rain
Snow
Ice Pellets (Sleet)
Hail
Humidity
• Humidity is the measure of the amount of water in the
atmosphere.
• Low humidity means that the evaporation of sweat from our
body can take place easily because there is a lot of room in
the air for it.
• A high humidity means that sweat sticks to us because the
air already has a lot of moisture in it and there is no room
for extra moisture from us.
• Relative humidity is a measure of the moisture in the air
against the maximum amount of moisture the air could
actually hold at a given temperature. It measured as a
percent.
FIN