Atmosphere – a layer of gases surrounding the planet, such as Earth
Blizzard – A sever winter storm with large amounts of falling or blowing snow creating
low visibility. Winds must exceed a certain amount and visibility must be a certain
distance to be called a blizzard.
Coriolis Effect – Deflection of a moving object because of Earth’s rotation. Deflection to
the right in the northern and left in southern hemisphere.
Drought – extended period of unusually low precipitation producing shortage of water
for people animals and plants
Dust Storm – Storm that transports large amounts of airborne silt and clay. Visibility at
eye level drops significantly
FScale – Series of values from F0 to F5 that describes the intensity of a tornado.
Developed by Theodore Fujita.
Heat Index – Numerical value that describes a persons perception of air temperature by
taking into account relative humidity.
Ice Storm – A period of freezing rain during which thick layers of ice accumulate on
Lightning – Natural high voltage electrical discharge between a cloud and the ground.
Relative Humidity – Ratio of the amount of water vapour in air to hypothetical amount
that would saturate the air at a given temperature and pressure.
Tornado – A violently rotating funnelshaped column of air extending downward from a
severe thunderstorm to the ground.
Troposphere – Lower most layer of the atmosphere. Characerized by a decrease in
temperature with altitude.
Wind Chill – Additional cooling affect that wind has on humans in cold weather.
Wind Sheer – a sudden change in direction or speed of wind in a short distance.
Watch – An alert issued by a meteorological agency that weather conditions are
favourable for sever weather such as tornadoes. Front – boundary between cool and warm air masses.
Cold Front – forms when cool air moves into a mass of warm air. Opposite for a warm
Stationary Front – boundary that does not move much.
• Storm usually develops when a fast moving cold front comes into contact with a
slow moving warm front. Cold overtakes the warm front and com