Download Weather Fronts

Weather Fronts
Part 2
Mrs. Nagrone
Objectives
• You will have the understanding of how air
masses and the collision of air masses cause
weather conditions.
• You will also be able to identify which air
masses, global wind belts, and types of
fronts usually control weather in the US.
Air Masses
• Air pressure is the weight
of air pressing down on an
area.
• A change in air pressure
usually means a change in
weather.
• When a new system
arrives it will have a
different amount of air
pressure.
Wind Belts
• Polar Easterlies:Cold wind from
the east.
• Prevailing Westerlies: Blowing
from west to east.
• Northeast Trade Winds: Winds
from Europe to N. America.
• Southeast Trade Winds: Blow
from SE to NW.
• Prevailing Westerlies:Cause the
weather in Africa and S.
America.
• Polar Easterlies:Move polar air
toward the equator to keep
temp. in balance.
Fronts
• The border between two
air masses that collide is
called a front.
• The masses usually do not
mix but rather the faster
pushes out the slower.
• The warmer air will
always be pushed up over
the denser, cooler air.
• There are four types of
fronts.
Warm Front
• When a warm mass moves
into an area of cooler air
the boundary that forms is
called a warm front.
• Warm air rises and cool air
is lower.
• High cirrus clouds usually
precede a warm front.
• They are followed by
lower clouds causing
precipitation.
Cold Front
• The leading edge of a cold
air mass causes a cold
front as it collides with
warm air.
• Cold fronts travel quicker
than warm and are more
extreme.
• The cold dense air pushes
under the warm moist air
causing condensing.
• Usually heavy
precipitation is evident.
Stationary Fronts
• When the boundary
between two fronts does
not move it is called a
stationary front.
• Air masses mix and clouds
form on both sides of the
front.
• When a warm front or
cold front stalls it is called
a stationary front.
Occluded Front
• This front is what happens
when a cold front
overtakes a warm front.
• The cold mass pushes all
the way under the warm
mass until it reaches the
cold mass ahead of the
warm mass.
• The warm mass is trapped
above the cooler air.
• Precipitation flows light
and steady in this front.
Water Cycle and Weather
• The heat from the sun
generates the energy
needed for the water
cycle.
• Heat is needed for
evaporation and
condensation to occur.
• Water from oceans, lakes
and rivers provides what
we need for precipitation
to “recycle”.
Summary
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Air masses that pass over an area control its weather.
A front is where two air masses collide.
Warm fronts bring steady rain and cloudy skies.
Cold fronts move quickly with strong storms.
Fronts that stay in place are called stationary fronts.
When a cold front overtakes a warm front an occluded
front forms.
• The water cycle provides the moisture needed to form
clouds and precipitation.