Weather Patterns 24.5

Air Masses

Fronts

Storms

Air Mass

• A large body of air with uniform Properties

–Temp—Moisture—Altitude

• Can cover large portions of continent

What Influences Air Masses?

• Influenced by region

–Ex. Gulf of Mexico = Moist hot weather

–Ex. NW Canada = Cold dry weather

What Influences Air Masses?• Where does it form:

–Over water = moisture

–Over land = dry–Latitude = polar =

cold –Latitude = tropical /

equator = warm

Fronts• Boundary between two air masses

• Air masses move because the Jet stream pushes air masses

•Cold Front:when a cold air mass moves over a warm air mass

Warm Front:• when a warm-air mass over

takes a cold dry air mass

Fronts• Stationary Front: when two fronts

overrun each other and it

stays… – no

movement

Front• Occluded Front: when a warm

front is caught between two cold fronts/masses

Low and High pressure systems• Cyclones have a center of low air

pressure. They circulate counterclockwise. –They are associated with clouds,

precipitation and storms.• Anticyclones have a swirling center

of high air pressure–They are associated with clear skies

and calm conditions

Storms• Thunderstorm includes thunder and lightening

–Form when air rises in a cumulonimbus cloud

• Tornado is an intense windstorm in a rotating column of air that touches the ground

Hurricane is a large tropical cyclone with at least 74 mph winds

Hurricane Katrina – Aug. 2005

Predicting weather

24-6

Weather Forecasting• Meteorologists are scientists who

study weather• Doppler Radar uses Doppler effect to

bounce waves off of precipitation in the atmosphere.

• Weather stations use instruments to gather weather information.

• Computers compile and analyze weather data to help predict forecasts

Weather Maps• They show predicted temps and indicate cloud

cover, precipitation and fronts• Isotherm is a line on a map that connect points

of equal temperatures• Isobar isa line thatconnects points of equal air pressure