Wind & WeatherBasics

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/wk3/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 PressureLots 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 Fronts2 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