Transcript air masses & fronts

AIR MASSES & FRONTS
Air masses can travel away from the regions where they form.
They move with the global pattern of winds. In most of the
United States, air masses generally move from west to east. They
may move along with the jet stream in more complex and
changing patterns.
Air Masses
• A large body of air with similar temperature
and moisture.
• Air masses form over large bodies of water or
land masses and are named by where they
form…over land-continental or over watermaritime and also named for where they
originate from-near the tropic-tropical and
from near the poles-polar
Description of air masses:
– Continental polar (cP)- cool (cold) and dry;
high pressure
• Continental arctic-(cA) type of continental polar mass that is very
cold & dry-forms over the arctic circle
– Continental tropical (cT)- warm (hot) and
dry; usually high pressure
– Maritime polar (mP)- humid (wet) and cold;
unstable-typically low pressure
– Maritime tropical (mT)- humid (wet) and
warm; unstable-low pressure
Interactive Air Mass Link
• http://www.usatoday.com/weather/tg/wams
orce/wamsorce.htm
FRONTS
• The boundaries between two air masses; the
leading edge of an air mass
• Different types of weather are brought about
or left behind after the different fronts-warm,
cold, stationary, or occluded
Cold Fronts
• A cold air mass is replacing a warm air mass.
• Shown on a weather map by a blue line with
triangles pointing the direction in which the
cool air (front) is moving.
• Low air pressure is found along the leading
edge of a cold front which is why there is a
chance of thunderstorms or severe weather
when they pass through.
• High air pressure is associated with cold fronts
which means sunny and fair weather.
Weather Map
Warm Fronts
• A warm air mass replacing a cold (cooler) air
mass.
• Shown on a weather map by a red line with
half circles pointing the direction in which the
warm air (front) is moving.
• Low pressure is associated with warm fronts
which means cloudy, overcast, drizzly, and
possibly rainy weather.
Weather Map
Comparing Warm and Cold Fronts
• Cold fronts move faster than warm fronts. (denser
air=more momentum and force)
• The weather activity in a cold front is often violent and
happens directly at the front.
• Cold fronts have sudden gusty winds high in the air
creating turbulence .
• Cold fronts bring beautiful weather while warm fronts
can bring dreary weather.
• The weather activity in a warm front generally happens
before the front passes through an area. Steady rain or
drizzle may fall for a long period of time.
• In a warm front the cloud formation is very low often
creating situations of poor visibility.
Occluded Front
•When a warm front is trapped by (between)
two cold fronts.
•Shown on a weather map by a purple line with
alternating triangles and half circles pointing
the direction the front is moving.
Stationary Front
• A front that is not moving or is moving very
slowly.
• Shown on a weather map with alternating red
semicircles pointing away from the warm air
and blue triangles pointing away from the
cold air.
• Stationary fronts can cause many days of
unchanged weather conditions-usually cloudy,
rainy, dreary weather.
Weather Map
For current weather map….
• http://www.weather.com/maps/maptype/curr
entweatherusnational/uscurrentweather_larg
e.html
Practice & Assess
• Practice: Air Masses Over North America
Worksheet
• Assessment: Air Masses Practice Quiz
• http://www.quia.com/quiz/278988.html?AP_r
and=2099466504