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Weather and Climate
Part 2 - Storms
CGF3M
Crescent School
“When rain and thunder and lightning rumbled
through the sky over ancient Greece, the people
believed that Zeus, the celestial god of weather,
was showing his anger with the mortals”
We all love warm sunny days, but we also must get
clouds, rain, wind, snow etc.
Storms (Precipitation) occurs when air is cooled.
Warm air rises, cools, condenses, forms clouds
and it precipitates.
The way in which air is cooled is the theme for this
slide show.
The question we should ask ourselves at this point
is “How does air cool?”
Air can be cooled in three ways:
1. If air travels over a mountain it must rise.
OROGRAPHIC PRECIPITAION.
2. Air in a localized area is heated to the point
that the air around it is cooler. This heated air
rises and is replaced by the cooler air.
CONVECTIONAL PRECIPITATION
3. A large mass of air (air mass - large body of
air that develops over a part of the earth’s
surface and contains similar characteristics of
temp. and precip.) collides with another air
mass. This collision forces one air mass to
rise above the other. The warmer air mass
always rises above the cooler one.
CYCLONIC PRECIPITAION OR MIDLATITUDE STORMS OR FRONTAL
Clouds
• Cirrus: high-altitude, wispy clouds associated with
warm fronts.
• Stratus: grey, poorly defined clouds associated with
frontal precipitation
• Nimbostratus: low altitude clouds associated with
frontal precipitation
• Cumulus: fluffy, white clouds associated with fair
weather
• Cumulonimbus: low-altitude, fluffy, grey, rain-bearing
clouds associated with thunderstorms.
Clouds are simply rising air!
CONVECTIONAL PRECIPITATION
06_32a.jpg
OROGRAPHIC PRECIPITATION
Orographic
Patterns
FRONTAL PRECIPITATION
07_10.JPG
Air Masses
• Bodies of air that develop over large areas of
the earth’s surface.
– Air must stay over source region for a long period
of time to take on characteristics of that region
– Air must be stable
• Front: leading edge of an air mass
• Eg. Cold Front or Warm Front
We
will
see
this
image
again.
S. Ontario
warm front
low pressure cell
cold front
07_07.JPG
07_11.JPG
Jet Stream
Powerful air currents in the stratosphere that
influence the movement of storms. The Jet
Stream flows from west to east (follows the
rotation of the earth). The Jet Stream pushes
the Westerlies in the same direction. All major
storms over Ontario will generally flow from
west to east. The Jet Stream also influences the
position of the air masses that effect the North
American continent.
07_11a.jpg
07_11b.jpg
07_11c.jpg
07_12.JPG
07_12a.jpg
07_12b.jpg
07_12c.jpg
07_12d.jpg
07_12e.jpg
07_12f.jpg
07_18.JPG
Air Masses affecting North America.
How does
the Jet
Stream
play a role
in this?
Lake Effect
Weather Forecasting
• Thermometers, rain gauges, barometers, wind
vanes, etc.
• Weather stations are linked by GTS - Global
Telecommunications System - supplies data
from sources such as balloons, radar, and
weather satellites.
Weather Forecasting
• Synoptic Charts/Weather Maps - plotted
information recorded at weather stations
– includes temperature, barometric pressure, wind
speed and direction, cloud cover, sky cover, dew
point.
• Isobars: lines connecting places of equal
atmospheric pressure.
• Front: leading edge of an air mass
Weather Forecasting
• Very popular with the media - 5 day forecast.
• A lot of Technology is used on TV to show the
weather.
• Why this importance over Weather
Forecasting?
Flash Corner:
Cyclonic Precipitation
Warm/Cold Front
THE END
GO TO THE THIRD AND FINAL
PART - VIOLENT STORMS