Transcript Forecasting the Weather

• Sun = Energy driving weather
• Equator = warm; Poles = cold
 why?
• Daytime: air over land warmer than
over water; reverse at night  why?
• Convection currents  explain!
large bodies of air classified by
* temperature (warm/cold)
* amount of water vapor (wet/dry)
Characteristics of air masses are
the same as those of the area
over which it forms.
4
Wet &
Cold
Can you describe
the air masses on
the map that
affect weather in
the United
States?
Dry &
Cold
2
Dry &
Warm
6
Wet &
Warm
5
1
Wet &
Warm
3
Dry &
Warm
• Leading edge of
an air mass
• 4 kinds of
fronts:
– Cold front
– Warm front
– Stationary front
– Occluded front
front
boundary
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Cold Front: mass of cold air moving into
area of warmer air
Warm Front: mass of warm air moving into
area of cooler air
Stationary Front: masses of cold & warm
air meet from opposite directions and stop
moving
Occluded Front: mass of cold air overtakes
mass of warm air moving in same direction


mass of cold air moving into area of warmer air
cold air forces warm air up & over the cold air;
often creating storms
Image courtesy of
PhysicalGeogrpahy.net


mass of warm air moving into area of
cooler air
As front enters, rain showers, then light
rain, then clearing and warmer
Image courtesy of
PhysicalGeogrpahy.net
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air masses are not moving against each other
forms when a cold front or warm front stops moving
may stay put for days
often cloudy with rain or snow

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forms when a cold air mass overtakes a warm front
Light to moderate rain before and during
Clearing and cooler after
Image courtesy of the
University of Illinois
WW2210.
Jet Stream – is a band
of fast moving air in
the stratosphere.
Formed where
Westerly winds meet
the Easterly winds
Jet Stream Video 1
You are planning
to travel to
Alabama in 2
days. The high
temperature
there for today
is 68º F.
Use the map to help you predict whether the
temperature in Alabama will increase, decrease, or stay
the same. Explain why you think so.
Weather Fronts
18
There is a cold front approaching. The
temperatures will probably be cooler
behind the front.
19
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Of course, meteorologists
(weather forecasters) use
much more data than fronts
and air masses to help them
forecast the weather more
accurately. But any forecast
is just a prediction of what
might happen. Even with the
best data, weather forecasts
can be wrong.
Temperature
Thermometers
Wind Speed
Wind Direction
Wind vanes
Anemometer
Humidity & Dew Point
Precipitation
Psychrometer
Rain Gauges
Air Pressure
Barometers