Forecasting the Weather

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Forecasting the Weather

• Pgs. 54 - 57

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Whats it like outside?

• At some point you have probably gone outside
  wearing clothes that did not prepare you
  properly.
• Weather affects what you wear and possibly the
  places you go.
• A weather forecast is a prediction of weather
  conditions over the next 3 to 5 days.
• Meteorologists predict the weather after
  observing and collecting data on current weather
  conditions.

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Weather Forecasting Technology

• To predict the weather, we need to measure air
  pressure, humidity, precipitation, temperature,
  wind speed and wind direction.
• To measure these atmospheric conditions we need
  to use special equipment.
• For humidity, we use a psychrometer and for
  precipitation we use a rain gauge.

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Measuring Air Temperature

• To measure air temperature we use a thermometer.
• A standard thermometer uses a liquid sealed in a
  narrow glass tube.
• When the temperature increases or decreases so
  does the liquid in the tube.
• Temperature can be measured in degrees Celsius or
  Fahrenheit.

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Measuring Air Pressure

• A barometer is an instrument used to measure air
  pressure.
• An accurate type of barometer is a mercurial
  barometer that uses a glass tube sealed at one
  end.
• Mercury is the liquid used.
• Air pressure moves the liquid
• as pressure changes.

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Measuring Wind Direction

• Wind direction can be measured using a windsock
  or wind vane.
• A windsock is a cone-shaped bag open at both
  ends.
• The wide end is open to the direction the wind is
  coming from.
• A wind vane is a shaped like an arrow with a
  large tail and is attached to a pole.
• The arrow points into the wind.

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Measuring Wind Speed

• Wind speed is measured by an anemometer.
• It consists of three or four cups connected by
  spokes to a pole.
• The wind pushes on the hollow sides of the cups,
  causing them to rotate on the pole.
• The motion causes an electrical current that is
  measured and displays a speed.

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Measuring Weather in the Upper Atmosphere

• In order to study the weather in the upper
  atmosphere, you need to collect data from higher
  altitudes.
• To do this you can use a weather balloon, radar
  or satellites.
• Weather balloons carry equipment and measure up
  to 30 km above the Earth.

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Radar and Weather Satellites

• Radar is used to find the location, movement, and
  intensity of precipitation.
• The type of precipitation can also be detected.
• Weather satellites are orbiting the Earth and can
  provide the images of swirling clouds you can see
  on television weather reports.
• They measure wind speed, humidity and temperature
  at different altitudes.

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Weather Maps

• In the U.S., there are two major sources used to
  collect and analyze weather data National
  Weather Service (NWS) and the National Oceanic
  and Atmospheric Administration (NOAA).
• They produce weather maps based on information
  from over 1000 weather stations.
• On the maps, each station is represented with a
  station model with symbols describing its data.

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Pressure

• Weather maps include lines called isobars.
• These are lines that connect areas of equal
  pressure.
• Areas they encircle are marked on maps as either
  High or Low Pressure.

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