Download P4 – Severe Weather Phenomena

W4 – Severe Weather
Temperature
 Is
a measure of the heat (energy) of an
environment
Precipitation
 Any
form of water includes
Rain,
snow, sleet, hail, and fog
Atmospheric Pressure
 The
pressure exerted on the surface of
earth as a result of gravity pulling on the
air column above it
Humidity
A
measure of the amount of water
vapour in the air
Wind Speed and Direction
 Air
moving from an area of high
pressure to low pressure
Sky Cover
 The
types of clouds present in the sky
Air Masses
A
large region of atmosphere where
the temperature, density, and
humidity are the same to the
properties of the land beneath it
Form over tropical or polar regions
High Pressure System
 When
an air mass cools over a cold
region on land
 Air loses energy, the particles in air
move slower, they can be closer to one
another thus they produce dense air.
 The denser air sinks, as it sinks it
warmer and capable of holding more
water vapour making it dryer.
Low Pressure System
 When
air mass travels over warm land
 The air mass warms, it expands and
rises, the rising air mass cools
 The air may condense, producing
clouds or precipitation
 At the Earth`s surface the atmospheric
pressure decreases so air flows toward
the low pressure area.
Fronts
 The
edge or boundary of an air mass
Cold Front
 When
cold, dense air displaces warm air, it
forces the warm air, which is less sense, up
along a steep slope
Warm Front
 Advancing
warm air displaces cold air along
a warm front, which develops a gradual
boundary slope
Stationary Front
 When
two air masses meet but neither
advances, the boundary between them
stalls.
 The
resulting stationary front often occurs
between air masses that have small
temperature and pressure differences.
Occluded Front (blocked or obstructed)
 Sometimes
a cold air mass moves so fast
that it overtakes a warm front, forcing the
warm air up.
 As
the warm is lifted, the advancing cold
air mass collides with the cold air mass in
front of the warm front.