Air Masses Fronts Cyclones/Anticyclones Weather Patterns Air Masses Fronts Cyclones/Anticyclones

Air Masses Huge body of air w/similar: Temperature Humidity pressure

Classifying Air Masses Temperature warm: tropical- form in tropics; low pressure cold: polar- form in polar regions; high pressure Humidity humid: maritime- form over oceans dry: continental- form over land in middle of continents

Four Major Air Masses Maritime Tropical Maritime Polar Warm, humid air masses Form over Gulf of Mexico & Atlantic Ocean- influence southeastern U.S. West- form over Pacific Ocean Maritime Polar Cool, humid air masses North Pacific & Atlantic Oceans Affect west coast more than east coast; Why?!

Four Major Air Masses http://www. classzone Continental Tropical Hot, dry air masses Form only in summer over Southwest & N. Mexico Cover smallest area in U.S. Continental Polar Cool, dry air masses Form over central & northern Canada & Alaska

Fronts As air masses move, they bump into each other & do not mix easily. Front- area where 2 air masses meet Often cause storms & changeable weather Type of front depends on characteristics of air masses & their movement

Cold Fronts Rapidly moving cold air mass runs into slower moving warm air mass Cold air slides under less dense warm air pushing warm air up Move quickly causing abrupt weather changes Clouds- cumulonimbus clouds, followed by altocumulus & clearing After front- cool & dry

Cold Front Before During After Winds S-SW Gusty/shifting W-NW Temperature Warm Sudden drop Steadily dropping Pressure Falling steadily Minimum, then sharp rise Rising steadily Clouds Ci, Cs, Cn Cn Cu Precipitation Short showers Heavy rains, possible, thstorms Showers; clearing

Warm Front Moving warm air mass collides with slowly moving cold air mass Warm air moves over cold air Humid warm air produces showers & light rain along front or scattered clouds if dry May be foggy or rainy for several days Clouds- cirrus, becoming cirrostratus; altostratus thickening & lowering becoming nimbostratus After front- warm & humid

Warm Front Before While After Winds S-SE Variable S-SW Temperature Cool-cold; warming Steady rise Warmer, then steady Pressure Falling Leveling off slight rise, then fall Clouds Ci, Cs, As, Ns, St, fog; occas.Cb in summer stratus-type clearing w/ scattered Sc; occas.Cb in summer Precipitation Lt.-mod. rain, snow, sleet, or drizzle Drizzle or none Usu. None, possl. lt. rain showers

Stationary Fronts Cold & warm air mass meet, but neither has force to move the other May produce rain, snow, fog, or clouds May bring clouds & precipitation for many days

Occluded Fronts Most complex weather situation Warm air mass caught between 2 cooler air masses Temperature near ground becomes cooler Warm air mass cut off or occluded May be cloudy, rainy, or snowy Clouds- warm sector: cumulus, stratocumulus

Cyclones Swirling center of low air pressure Counterclockwise spin of winds towards low pressure Associated w/storms & precipitation

Anticyclones High pressure centers of dry air Winds spiral outward from high pressure spinning clockwise Dry, clear weather

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