Pressure Systems and Weather Fronts

Pressure SystemsLow pressure: an area where the

atmospheric pressure is lower than the surrounding areaAir rises then it cools and condensesWeather: cloudy and rainy

Pressure SystemsHigh pressure: an area where the

atmospheric pressure is higher than the surrounding areasAir is sinking Weather: light winds, dry, clear skies

High vs. Low pressure air movement LOW PRESSURE HIGH PRESSURE

Warm FrontWarm air mass moves into

a cold air massWeather: overcast or rain http://www.phschool.com/atschool/

phsciexp/active_art/weather_fronts/index.html

Cold FrontCold air mass gets pushed into warm air massWeather: Abrupt weather changes http://www.classzone.com/books/earth_science/terc/content/

visualizations/es2002/es2002page01.cfm?chapter_no=visualizatione

Occluded FrontsA warm air mass is caught

between 2 colder air masses

Weather: Severe storms

Stationary FrontWarm and cold air mass meet but neither has

greater force behind it to move the other mass

Weather: Fog, clouds, rain, snow

Severe WeatherThunderstorm: rain, hail, wind and lightning

Formation: rapidly rising air, warm or cold front

Lightning: small ice crystals that are positively charged collide with large ice crystals that are negatively charged

Tornado: a violently rotating column of air extending from a thunderstorm cloud

Severe WeatherCyclone: a tropical storm that is a low

pressure region surrounded by spiral thunderstorms that produces heavy rain and strong winds

Hurricane: a tropical cyclone that forms in the southern Atlantic, Caribbean Sea or the Gulf of Mexico

Severe WeatherBlizzard: a severe snow storm characterized

by strong winds and heavy snowfallDrought: an extended period of time when a

region does not receive rainfallFlash Flooding: rapid flooding caused by

heavy rainfall or rapid snow and ice melt

Severe WeatherEl Nino: The abnormal warming of the Pacific

OceanCauses: droughts in Asia, Flooding in Americas

La Nina: The abnormal cooling of the Pacific OceanCauses: flooding in Asia, Droughts in Americas

Severe WeatherMonsoon Wind: a change in the direction of

the wind due to abnormal heating of the surface of Earth

Monsoon Rain: a rainy season that can last for months caused by the change in wind direction