FORECASTING

THEWEATHER

FORECASTING

THEWEATHER

• Sun = Energy driving weather• Equator = warm; Poles = cold

why?• Daytime: air over land warmer than

over water; reverse at night why?• Convection currents explain!

Key Atmospheric Concepts

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.

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.

Air Masses

Can you describe the air masses on

the map that affect weather in

the United States?

Can you describe the air masses on

the map that affect weather in

the United States?

5

4

1

3

2

Wet & Warm

Wet & Warm

Dry & Warm

Dry & Cold

Wet & Cold

Air Masses

6Dry & Warm

• Leading edge of an air mass

• 4 kinds of fronts:– Cold front– Warm front– Stationary front– Occluded front

front boundary

Frontal Boundaries

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

Weather Terms/Symbols

Cold FrontCold Front 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

Warm Front 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

Stationary FrontsStationary Fronts 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

Occluded FrontsOccluded Fronts 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

.

Locate the types of frontsLocate the types of fronts

Cold FrontsCold Fronts

Warm FrontWarm Front

Stationary FrontStationary Front

Occluded FrontOccluded Front

Jet Stream – is a band of fast moving air in

the stratosphere.

Formed where Westerly winds meet the Easterly winds

Jet Stream Video 1

Weather Fronts 18

Be a Weather ForecasterBe a Weather Forecaster

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.

19

Be a Weather Forecaster

There is a cold front approaching. The temperatures will probably be cooler behind the front.

There is a cold front approaching. The temperatures will probably be cooler behind the front.

Be a Weather Forecaster 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.

Meteorological ToolsTemperature Wind Direction Wind Speed

Precipitation

Humidity & Dew Point

Thermometers Wind vanes

Air Pressure

Rain Gauges

Anemometer

Psychrometer

Barometers