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WEATHER. By: Mrs. Nicholson. How Clouds Form. How Clouds Form. The sun heats the ground. The warm ground heats the air above. Water evaporates from oceans, rivers, the ground or wherever water is. Warm air rises carrying water vapor with it.

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By mrs nicholson l.jpg


By: Mrs. Nicholson

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How Clouds Form

  • The sun heats the ground.

    The warm ground heats the air above.

  • Water evaporates from oceans, rivers, the ground or wherever water is.

  • Warm air rises carrying water vapor with it.

  • When the air cools, the water vapor becomes water droplets.

  • A cloud is made by these tiny drops of water.

    Water in the form of a gas is water vapor.

    Evaporate means to change from a liquid state to a gas.

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Cloud Cover in the Sky

  • CLEAR- no clouds, less than 10%

  • SCATTERED- clouds cover 10-50%

  • BROKEN- clouds cover 50-90%

  • OVERCAST- clouds cover over 90%

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The word cirrus comes from the Latin word for a tuft or curl of hair.

Cirrus clouds are very wispy and feathery looking.

Cirrus clouds are composed of ice crystals and are so thin that sunlight can pass right through them.

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The word stratus comes from the Latin word that means "to spread out."

Stratus clouds are horizontal, layered clouds that stretch out across the sky like a blanket. Sometimes a layer of warm, moist air passes over a layer of cool air. Stratus clouds often form at the boundary where these layers meet.

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The word cumulus comes from the Latin word for a heap or a pile.

Cumulus clouds are puffy in appearance. They look like large cotton balls.

Cumulus clouds usually form when warm, moist air is forced upward. As this air rises, it is cooled. If it is cooled below its dew - point temperature, condensation will occur.

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  • An air mass is a large amount of air that has the same temperature and humidity.

  • An air mass can be hundreds or thousands of miles across.

  • As air masses move, they can bring certain weather conditions with them.

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  • When two air masses of different temperatures or humidities bump into each other, a weather front forms.


    boundary between two air masses

  • Warm Front

  • Cold Front

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  • Cold air pushes under a Warm air mass.

  • The warm air rises and cools.

  • If there is enough moisture, clouds may form and rain/snow may fall.

  • When really cold and dry air pushes into very warm/moist air, violent thunderstorms may form.

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  • Warm air pushes over a cold air mass. (which is lighter than cold air)

  • The gradual uplift cools the warm moist air and often produces clouds and rain, drizzle or snow.

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  • Air Pressure is the amount of air that presses or pushes on anything.

  • Air moves from a high pressure to an area of low pressure. This moving air is called wind.

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  • Warm air rising causes a low pressure area.

  • There is less pressure because the air is lighter.

  • Low pressure areas often have weather that is cloudy with precipitation.

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  • Cool air sinks because it is heavier than warm air.

  • It pushes on the earth’s surface with more pressure.

  • High pressure usually indicates clear or fair weather.

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Measure Weather

  • To measure weather, there are different instruments that can be used.

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An anemometer is an instrument used to measure wind speed.

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A barometer is an instrument used to measure air pressure.

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A hygrometer is a weather instrument used to measure air humidity.

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Rain Gauge

A rain gauge is an instrument used to measure the amount of precipitation.

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A thermometer is an instrument used to measure temperature.

Temperature is measured in Fahrenheit or Celsius degrees.

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Wind Vane

A wind vane is an instrument used to measure wind direction.

More Information on Weather Instruments

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  • Any form of water particles that fall from clouds and reach the ground.




    Freezing Rain


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Blizzard-Violent Winter Storm

  • Lasting at least 3 hours

  • Freezing temperatures

  • Strong winds of 35 mph or more

  • With blowing snow

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  • Warm core tropical cyclone

  • Maximum surface wind of 74 mph or greater

  • Winds blow in a large spiral around a relatively calm center of extremely low pressure known as the eye.

  • Around the rim of the eye, winds may gust to more than 200 mph.

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Tornadothe most violent weather phenomena


A violently rotating storm of small diameter;

It is produced in a very severe thunderstorm

Appears as a funnel cloud extending from the base of a Cumulonimbus to the ground.

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  • a huge wave

  • caused by undersea earthquakes, volcanic eruptions