Download Weather Lesson Seven

Weather Lesson Seven
Air Masses and Fronts
AIR MASSES
• Large bodies of air in the troposphere with
similar temperature, moisture and pressure
characteristics.
• Forms over large areas called source
regions.
• Air mass stays over an area for a while to
pick up characteristics of that region.
AIR MASS SOURCE REGIONS
1. POLAR (P) - cool air from the north
(Canada or Arctic).
2. TROPICAL (T) - warm air from the
south.
3. CONTINENTAL (c) - air mass formed
over land - DRY.
4. MARITIME (m) - air mass formed over
water - MOIST.
m
c
P
cT - dry and warm
cP - dry and cold
mT - moist and warm
mP - moist and cold
T
mP
cA
mP
cP
cT
mT
mT
FRONTS
• The boundary between two air mass.
• Little mixing of air occurs at fronts.
• Unstableness of fronts is the cause of
precipitation.
• 4 types of fronts and they are . . .
COLD FRONT
• The boundary between an advancing air
mass pushing a warmer air mass.
• Underlying cold air pushes warm up and
over like a plow.
• A fast moving front.
• Symbol used on maps is
WARM FRONT
• The boundary between an advancing warm
air mass on a retreating wedge of a cold air
mass.
• Warm air rises up and over as its advances
because it is less dense.
• A slow moving front.
• Symbol used on maps is
OCCLUDED FRONT
• Occurs when a cold front overtakes a warm
front and pushes the warm air between them
up off the ground.
• Symbol used on maps is
STATIONARY FRONT
• Boundary between two adjacent air masses
of different characteristics remaining in
approximately the same position.
• Symbol used on maps is
Symbols point in the direction the air mass is moving.
WAVE CYCLONE
• The typical pattern of storms (or low
pressure systems) as they travel across the
United States.
• Storms have a low pressure center with a
wedge of a cold front and a warm front
extending from the center.
L
STORM TRACKS
• Low pressure storms generally track (move)
to the east (or northeast) across the United
States.
• Due to the wind belt in which the United
States is located.
WEATHER PREDICTION
• Weather prediction is based on probability.
• A few days predictions are more accurate
and reliable than long term predictions.
• Computer analysis and satellite images have
improved forecasting in recent years.