Download Weather Systems

Weather Systems
Weather
• Weather: the current conditions of the atmosphere
• Included in a weather report: Air temperature, air
pressure, cloud type, wind speed and direction, the
amount and type of precipitation, moon phase
Weather
• Meteorology: the study of atmospheric changes
• Weather changes every day because the air is always
moving
• Weather also changes because the energy from the sun
is constantly being moved around after it reaches
earth’s surface
Weather
• Climate: the long term weather patterns of a certain area
• Climatology: the study of the climate and climate change
• Weather can change rapidly, climate changes slowly over
time
Pressure Systems
• Air wants to move from areas of high pressure to areas of
low pressure
• Low pressure system: the air has a lower pressure than the
surrounding air
Low Pressure Systems
• The air rises and the water vapor
condenses into clouds
• Low pressure systems bring:
cloudy weather and storms are
likely
High Pressure System
• High Pressure Systems: the air has a higher pressure than
the surrounding air
• Remember: Air always wants to move from a high
pressure to a low pressure!
High Pressure Systems
• As the air sinks, water
evaporates becoming water
vapor
• High pressure systems bring
good weather and clear skies
Pressure Systems
Low Pressure
Up and in
High Pressure
Down and out
Weather Fronts
• Weather front: an area where two air masses with
different temperatures and densities collide but do
not mix
• The collisions often cause storms and changing
weather
Warm Front
• Warm front: a warm air mass is pushed up and over a
cold air mass
• As a warm front approaches, the temperature and air
pressure drop
• Warm fronts move slowly and bring clouds and
rainstorms
Cold Fronts
• Cold Front: a cold air mass pushes a warm air mass up
• Cold fronts move fast and produce dramatic changes in
weather
Cold Fronts
• As the cold front passes, the winds become gusty, and
the temperature drops rapidly
• Cold fronts bring heavy rain, snow, hail, thunderstorms
and cooler weather
Stationary Fronts
• Stationary Front: when a warm air mass and a cold air
mass push against each other but neither one can
move the other
Stationary Front
• A stationary front may stay for days
over an area
• During a stationary front, weather is
cloudy and rain or snow often falls
Occluded Fronts
• Occluded Front: when a warm air mass and a cold air
mass push into each other and the cold air mass
overtakes the warm air mass
Occluded Front
• Occluded fronts form around low pressure systems
• Occluded fronts cause changes in temperature and
wind direction
Severe Weather
• Thunderstorms: rain, hail, wind and lightning
• Thunderstorms form when air rapidly rises in a low
pressure system
• https://www.youtube.com/watch?v=QVZExLO0MWA
Thunderstorms
• Lightning: small ice crystals that are positively charged
collide with ice crystals that are negatively charged
• Thunderstorms are measured on a scale of 1 to 5, 5 is
very severe
Severe Weather
• Hurricane: a storm with violent wind exceeding 74 mph
• Hurricanes are measured on a scale of category 1 to
category 5
• Category 5 is catastrophic
• http://www.cotf.edu/ete/modules/sevweath/swwhatare.h
tml
Severe Weather
• Tropical Storm: a hurricane that forms in a tropical area
• Cyclone: a tropical storm surrounded by thunderstorms
Severe Weather
• Tornado: a mobile, destructive vortex of violently rotating
winds
• Tornadoes are measured on a scale from F0 to F5, F5
tornadoes are the most destructive
• why tornadoes hate America
Severe Weather
• Blizzard: a severe snow storm with strong winds and
heavy snowfall
• Drought: an extended period of time when a region does
not get rain
Severe Weather
• Flash flood: rapid flooding caused by heavy rainfall or
rapid snow melt
• The ground is too frozen, too saturated or too dry to
soak up the water fast enough
Severe Weather
• Monsoon Wind: a change in the direction and strength of
the wind
• Monsoon rains: a rainy season that can last for weeks or
months
Severe Weather
• El Niño: the abnormal warming of Pacific ocean currents
• Causes droughts in Asia and flooding in the Americas
La Niña
• La Niña: the abnormal cooling of Pacific ocean currents
• Causes flooding in Asia and droughts in the Americas