Understanding weather
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Understanding Weather. Weather and Water Cycle. Weather – condition of the atmosphere (mixture of gases) at a certain time and place Mainly affected by amount of water in the air. Humidity. As water evaporates from lakes, oceans, and plants it becomes water vapor.

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Weather and water cycle
Weather and Water Cycle

  • Weather – condition of the atmosphere (mixture of gases) at a certain time and place

  • Mainly affected by amount of water in the air


  • As water evaporates from lakes, oceans, and plants it becomes water vapor.

  • Humidity – amount of water vapor in air

  • When temp increases so does amount of air’s ability to hold water vapor

Relative humidity
Relative Humidity

  • Amount of water vapor in the air compared with the maximum amount of water vapor that the air can hold at a certain temperature

  • Given as a percentage

  • When air is able to hold all of the water it can at a given temp., it is called saturated (100% relative humidity)

Dew point
Dew Point

  • Dew point is the temperature at which a gas condenses (changing state) into a liquid.

  • At dew point, air is saturated


  • A collection of small water droplets or ice crystals suspended in air, which forms when the air is cooled and condensation occurs

  • Clouds are classified by form and altitude

Types of clouds
Types of Clouds

  • Cumulous – fair weather

  • Stratus – layered, block out sun

  • Cirrus – thin, feathery

  • Nimbus – produce precipitation

  • Cumulonimbus = thunderstorms

  • Nimbostratus = light to heavy rain


Types include:

  • Rain – most common… interesting fact: before a water drop can fall as rain, it must become about 100x its original size

  • Sleet – rain fallws through layer of freezing air

  • Snow – when water vapor changes directly to a solid when temps are super cold

  • Hail – updrafts of raindrops freeze, water recoats it, updraft, repeat….

Air mass
Air Mass

  • Large body of air where temperature and moisture content are constant throughout

  • Maritime (Wet)

  • Continental (Dry)

  • Polar (Cold)

  • Tropical (Warm)


  • Air masses have different densities

  • they don’t mix

  • Warm air rises etc.

  • When two air masses meet it is called a Front

  • Types include: Cold, Warm, Occluded, Stationary

Cold front
Cold Front

  • Where cold air moves under warm air (Less Dense) and pushes warm air up

  • Move quickly

  • Bring Thunderstorms, Heavy rain, and snow

  • Usually cool weather follows

Warm front
Warm Front

  • Where warm air moves over cold, denser air

  • Warm air gradually replaces cold air

  • Bring drizzly rain and are followed by clear and warm weather


  • Small intense weather systems that produce:

  • Strong winds

  • Heavy rain

  • Lightening

  • Thunder

Lightening and thunder
Lightening and Thunder

  • Lightning - electric discharge that occurs between a positively charged area and a negatively charged area

  • Can happen between two clouds, Earth and a cloud, or even between two parts of the same cloud.

  • When lightening strikes, energy is released.

  • This energy is transferred to air and causes the air to expand rapidly sending out sound waves… Thunder is result


  • Only occur in 1% of all thunderstorms

  • Tornado – small, spinning column of air that has high wind speeds and low central pressure

  • Starts out as a funnel cloud that pokes through the bottom of a cumulonimbus cloud

  • Becomes tornado when it makes contact with ground


  • Large rotating tropical weather system that has wind speeds of at least 120km/h

  • Most powerful storms

  • Synonym – typhoon or cyclones

  • Mostly occur between 5 and 20 latitudes