Download air mass and front notes

What happens when air
masses meet?
What is an air mass?
Large volume of air with uniform
temperature and humidity readings
Gets its characteristics from where it forms
Continental: forms over land (dry)
Maritime: forms over water (moist)
Tropical: forms near equator (warm)
Polar: forms nearer poles (cold)
Continental Air Masses
Polar (cP)
Tropical (cT)
Maritime Air Masses
Tropical (mT)
Polar (mP)
What happens when different
air masses meet?
Boundary between two
different air masses is a:
FRONT
Types of Fronts
Cold Front
Warm Front
Stationary Front
Occluded Front
What happens in a cold front?
Cold air moves into warmer air
Cold Front
Cold air moves in, replaces warm air
Cold air is more dense than warm air
Cold air pushes warm air up
Tall clouds form (cumulus and
cumulonimbus)
Clouds are right along the front
Precipitation is brief, but heavy
(thunderstorms)
Band of precipitation 75 miles around front
(about 50 miles ahead and 25 miles
behind)
75 miles
Air pressure is lowest at front
After front passes: colder air mass
temperature drops
skies clear
pressure increases
Cold fronts move faster than warm fronts
(about 30 mph)
Weather map symbol
Warm air moving into cold
Predictions?
Warm air moving in
What happens with a warm
front?
Warm air mass advances and
replaces cold air mass
Warm air is less dense than cold
Warm air rides above the colder
air
Warm Front
Clouds start to form 1000 miles
ahead of the front
Cirrus clouds develop, followed
by lower level stratus clouds
Belt of precipitation is about 300
miles wide (starting 100-400 miles
ahead of the front)
1000 miles
Rain (precipitation) is gentle, but
may last for a long period (several
hours or days)
Weather changes slowly (front
moves about 20 mph)
Warmer air finally replaces the
colder air
As the front passes:
Temperature
increases
Skies clear
Pressure
increases
Weather map symbol
Fronts – boundary that separates
2 air masses with different
temperatures
Clouds: altostratus
Warm front
Cold Front
HINT: sudden burst of intense rain over a small area
Cold Front
HINT: this is a squall line
Cold front
Stratus clouds:
warm front
Clouds on Monday
Clouds on Tuesday
Warm front
Another squall line: COLD FRONT
Robin Brueckner 2004
HINT: low gray clouds, long period of light snow
WARM FRONT!!!!!!!!
Cold Front
Cold front
Sharp break between air masses
Stationary Front
Stationary Front
A stationary front occurs when the air masses
on either side of the front are not moving
toward each other.
Stationary Front
Neither air mass pushes into the
other
Generally causes unsettled conditions
–Rain, clouds, etc…
Flooding may occur if front does not
pass
OCCLUDED FRONT
Warm air mass gets caught between 2
colder air masses and is forced aloft
Formation of an Occluded Front
Occluded Front
A cold air mass catches up to another
cold air mass
Warm air is ‘squeezed’ out in the
middle
Causes precipitation
Important Vocabulary
Air mass
– (cT, cP, mT, mP, cA)
Front
Warm front
Cold front
Occluded front
Stationary front
High and counterclockwise into the
Low
Fronts are low pressure – lousy
weather
After the front passes – happy
weather
Weather in a High
Clockwise
Rotation
Bright, Clear
Happy Weather
Hurricanes – counterclockwise low
pressure systems (lousy weather)