Unit 4Unit 4WeatherWeather

Lesson 3Lesson 3How is Weather How is Weather

Predicted?Predicted?

Measuring WeatherMeasuring Weather The study of weather The study of weather

is meteorology.is meteorology. Meteorologists are Meteorologists are

people who study people who study weather.weather.

Weather instruments, Weather instruments, wind direction, and wind direction, and clouds can help make clouds can help make weather predictions.weather predictions.

ThermometerThermometer

Measures air Measures air temperaturetemperature

Air cools down Air cools down during the day or during the day or warms up at night → warms up at night → rain may fall soon.rain may fall soon.

BarometerBarometer

Measures air Measures air pressure pressure

Also called Also called barometric pressurebarometric pressure

Change in air Change in air pressure →change in pressure →change in weatherweather

AnemometerAnemometer

Measures wind Measures wind speedspeed

Change in wind Change in wind speed → change in speed → change in weatherweather

HygrometerHygrometer

Measures humidityMeasures humidity Increased humidity Increased humidity

→ about to rain→ about to rain

Air MassesAir Masses

Air moves in an air Air moves in an air mass, a large body of mass, a large body of air that has the same air that has the same temperature and temperature and humidity throughout.humidity throughout.

Air masses may be Air masses may be warm or cold and warm or cold and humid or dry.humid or dry.

Four Kinds of Air Masses that Affect Four Kinds of Air Masses that Affect

Weather in the United StatesWeather in the United States

Continental polar (cP) – cool, dry weatherContinental polar (cP) – cool, dry weather Continental tropical (cT) – hot, dry weatherContinental tropical (cT) – hot, dry weather Maritime polar (mP) – cold, humid weatherMaritime polar (mP) – cold, humid weather Maritime tropical (mT) – warm, humid weatherMaritime tropical (mT) – warm, humid weather

Warm FrontWarm Front

Forms where a warm Forms where a warm air mass moves over air mass moves over a cold air mass.a cold air mass.

As this happens, As this happens,

stratus clouds form. stratus clouds form. They produce rain or They produce rain or

snow that can last for snow that can last for hours.hours.

After a warm front After a warm front passes through an passes through an area, the weather is area, the weather is warmer and more warmer and more humid.humid.

Cold FrontCold Front

After a cold front After a cold front passes through an area, passes through an area, the weather is cooler the weather is cooler and drier.and drier.

Forms where a cold air Forms where a cold air mass moves under a mass moves under a warm air mass.warm air mass.

The warm air is pushed The warm air is pushed up and cooled. up and cooled.

This fast cooling and This fast cooling and condensation causes condensation causes heavy rains, heavy rains, thunderstorms, or thunderstorms, or snow.snow.

Cold fronts move Cold fronts move quickly, so these quickly, so these storms do not last long.storms do not last long.

Weather MapsWeather Maps

Weather maps Weather maps use symbols to use symbols to show the show the weather. weather.

A weather map A weather map can also give can also give information about information about temperature.temperature.

Weather SymbolsWeather Symbols

Forecasting WeatherForecasting Weather

Meteorologists make weather forecasts based on Meteorologists make weather forecasts based on data from weather stations, weather satellites and data from weather stations, weather satellites and special weather instruments. special weather instruments.

Variables that Affect Variables that Affect Weather ForecastsWeather Forecasts

Wind direction – Wind direction – Example: weather Example: weather blowing from the north blowing from the north will soon reach your areawill soon reach your area

Air pressure – Air pressure –

low-pressure: stormy low-pressure: stormy weather; weather;

high-pressure: fair weatherhigh-pressure: fair weather

Videos on WeatherVideos on Weather

How to Predict WeatherHow to Predict Weatherhttp://www.youtube.com/watch?v=YxH1xiNirhAhttp://www.youtube.com/watch?v=YxH1xiNirhA

FrontsFrontshttp://www.youtube.com/watch?v=vPC5i6w3yDI&feature=relatedhttp://www.youtube.com/watch?v=vPC5i6w3yDI&feature=related

Weather for Kids part 1 (15:00)Weather for Kids part 1 (15:00)http://www.youtube.com/watch?v=v1-Khi9i3UU&feature=relatedhttp://www.youtube.com/watch?v=v1-Khi9i3UU&feature=related

Weather for Kids part 2 (12:09)Weather for Kids part 2 (12:09)http://www.youtube.com/watch?v=IbRln1GIOdA&feature=relatedhttp://www.youtube.com/watch?v=IbRln1GIOdA&feature=related