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Wind & Weather
Basics
March 2014
Weather is always changing !
• Constant movement of air
• Changes in moisture
Air Mass
• Large body of air that has the same properties
as the surface over which it develops.
–Cold, Hot
- Wet, Dry
• These air masses move across the U.S. &
collide with each other creating fronts ….
Types of Air Masses
Weather Maps
Tuesday & Wednesday
Isotherms
Isobars
http://www.aos.wisc.edu/~aalopez/aos101/wk
3/wk3Pcont.jpg
How does weather affect you?
• Directly
–
–
–
–
Rain – floods/drought
Snow – closes school
Ice – no power
Tornado – destructive
• Indirectly
– Drought – food prices go
up
– Freeze in South – fruit is
destroyed
– Cold Weather – oil & gas
prices go up
What determines what the weather
will be today?
• Air pressure
• Wind
• Temperature
• Humidity
Wave Cyclones
• Low pressure areas
• Start to rotate
counterclockwise
• Bad weather
• Thunderstorms & rain
•
Air Pressure
• Low Pressure
• Few molecules in the
air
• “sucks in” bad
weather
Hurricanes = Tropical cyclones
• Also known as typhoons
• Speeds in excess of 120
km/hr
•
Thunderstorms
Tornadoes
Anticyclones
• High pressure areas
• Dry/clear weather
• Droughts
"High pressure is good; sunny weather
occurs when the pressure is high. Skies are
blue, winds are light and it never rains
when the barometer soars."
Air Pressure
• High Pressure
Lots of molecules in
the air
“pushes away” the bad
weather
Complete Venn Diagram for High &
Low Pressure Systems
03/22/2001 - Updated 02:02 PM ET
Source: USA TODAY research by Chad Palmer, Graphic by John He
03/22/2001 - Updated 02:36 PM ET
Source: USA TODAY research by Chad Palmer, Graphic by John Herne
Occluded Fronts
2 cold air mass meet
Pushing up the warm air that is
blocked in-between.
03/22/2001 - Updated 02:29 PM ET
Stationary Front
Each Front causes precipitation
Along each front warm air is pushed
upward, cooled in the atmosphere,
and becomes saturated
Types of Fronts
Start here on Wednesday
Weather Instruments & forecasts
Anemometer Measures wind speed
Wind
• Comes from North
=> Cold
• Comes from South
=> Warm
Fast or Slow ???
Weather Radar = Doppler Radar
Measuring air pressure with a
barometer
Humidity
Hot air can hold more
water vapor
Cold air is drier
& causes static
electricity in winter
Measured with a
psychrometer,
hygrometer, or a
Relative Humidity
• The amount of water
vapor in the air
compared to how
much it could hold.
ex.) 50%, 20%
• Saturated means
100%
• Measured with a
psychrometer.
Radiosonde =
package of weather
instruments
Climate: predictable weather patterns