Download Pressure Systems and Fronts

Pressure Systems
 Low pressure: an area where the atmospheric pressure
is lower than the surrounding area
 Air rises then it cools and condenses
 Weather: cloudy and rainy
Pressure Systems
 High pressure: an area where the atmospheric pressure
is higher than the surrounding areas
 Air is sinking
 Weather: light winds, dry, clear skies
High vs. Low pressure air movement
LOW PRESSURE
HIGH PRESSURE
Warm
Front
 Warm air mass moves into a cold
air mass
 Weather: overcast or rain
 http://www.phschool.com/atschool/phsciexp/act
ive_art/weather_fronts/index.html
Cold Front
Cold air mass gets pushed into warm air mass
 Weather: Abrupt weather changes
 http://www.classzone.com/books/earth_science/terc/content/visualizatio
ns/es2002/es2002page01.cfm?chapter_no=visualizatione
Occluded Fronts
A warm air mass is caught
between 2 colder air masses
Weather: Severe storms
Stationary Front
 Warm and cold air mass meet but neither has greater
force behind it to move the other mass
 Weather: Fog, clouds, rain, snow
Severe Weather
 Thunderstorm: 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 Weather
 Cyclone: 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 Weather
 Blizzard: a severe snow storm characterized by strong
winds and heavy snowfall
 Drought: an extended period of time when a region
does not receive rainfall
 Flash Flooding: rapid flooding caused by heavy rainfall
or rapid snow and ice melt
Severe Weather
 El Nino: The abnormal warming of the Pacific Ocean
 Causes: droughts in Asia, Flooding in Americas
 La Nina: The abnormal cooling of the Pacific Ocean
 Causes: flooding in Asia, Droughts in Americas
Severe Weather
 Monsoon 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