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WEATHER:
TOPIC 7
What is an air mass?
• An air mass is a large body of air in the
troposphere with similar characteristics of
pressure, moisture and temperature
How are air masses characterized?
• Air masses are characterized by the
regions in which they form over.
– cA- Continental Arctic
– cP- Continental polar
– cT- Continental Tropic
– mP- Maritime Polar
– mT- Maritime tropical
What are the characteristics of a
low pressure?
•The characteristics of a low pressure, also
called cyclones are:
-Lowest pressure at the center
-Winds blow toward the center
-Winds circulate counterclockwise
-Usually associated with stormy
weather & heavy cloud cover
What are the characteristics of a
high pressure?
• The characteristics of a high pressure,
also called anticyclones are:
– Highest pressure at the center
– Winds blow away from the center
– Winds circulate clockwise
– Usually associated with calm and
clear weather
What is a front?
A front is a boundary or interface between
two different air masses.
What are the different types of fronts?
• Different types of clouds are:
– Cold front- boundary between advancing cold air mass and
a warm air mass. The cold air pushes the warm air up like a
wedge.
– A warm front- boundary between advancing warm air mass
and a cold air mass. The warm air mass is forced to rise as it
advances
– An occluded front- boundary between a cold air mass, warm
air mass and a another cold air mass is sandwiches
between two air mass. (A sandwich)
– A stationary front- when 2 different air masses remain in the
same position
What is a storm? What are the
different types of storms?
• A storm is a violent or severe disturbance of
the atmosphere that usually creates
dangerous and destructive conditions
• Different types of storms include mid-latitude
cyclones, hurricanes, thunderstorms and
blizzards.
What is a mid-latitude cyclone or
cyclonic storm?
• A mid-latitude cyclone is a result from a
low pressure system.
• These storms bring precipitation to the mid
latitudes.
What is a hurricane and what are
its characteristics?
• A hurricane is a low pressure system in the tropics
in which winds blow at 74 mph or more
• They have rotating bands of precipitation, with a
cloudless “eye” at the center.
• They are rated on a Safir-Simpson scale (which
measure how much damage the storm causes).
What is a thunderstorm and what
are the characteristics?
• A thunderstorm is a heavy rainstorm
accompanied by thunder and lightening.
• Thunderstorms often form from uplifting of warm
air. The clouds associated with thunderstorms
are cumulonimbus clouds.
• They have 3 stages:
• Developing stage
• Mature stage
• Dissipating stage
What is a tornado?
• A tornado is a rapidly rotating extremely low
pressure funnel that hangs down from thunderstorm
clouds
• Most tornadoes only last a few minutes.
• 318 mph is the fastest recorded surface winds.
• Most damage is actually caused by flying objects
• Tornadoes are measured on a Enhanced Fajita
Scale (EF1, EF2, EF3, EF4….)
What is a blizzard?
• A blizzard is a storm with winds 35 mph or
greater associated with considerable
amounts of snow.