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Predicting the Weather
What’s the Weather?
• Look at the weather report in the newspaper. What conditions are predicted for today? Temperature, precipitation and wind speed.
• Write down the actual weather conditions right now. Does the weather report match what you observe? What is the same? What is different?
Weather Sayings
• Based on long-term observations—sailors, pilots, farmers..etc
• Evening red and morning gray will send the traveler on his way; evening gray and morning red will bring down rain upon his head
• Red sky in the morning, sailors take warning; red sky at night, sailor’s delight.
• Why does red sky in the morning mean bad weather?
• Recall—storms move from west to east
• Clouds in the west may indicate an advancing low-pressure area, bringing stormy weather
• If the clouds are high in the west, the rising sun turns these clouds red—the reverse is true at sunset
Weather Forecasting
• 1st step = collect data, either from simple, direct observations or through the use of instruments
• Example: If a barometer shows that air pressure is falling, you can expect a change in the weather—indicates an approaching low pressure area, possibly bringing snow or rain
Making Simple Observations
• Weather signs in the sky
• Cumulus clouds often form on warm afternoons when warm air is rising
– If they grow larger and taller, they become cumulonimbus, which may produce a thunderstorm
• Cirrus clouds high in the sky, a warm front may be approaching
Interpreting Complex Data
• Meteorologists are able to interpret information from a variety of sources, including local weather observers, instruments carried by balloons, satellites, and weather stations around the world.
• Meteorologists use maps, charts, and computers to analyze weather data and to prepare weather forecasts
• Radar is used to track areas of rain or snow and to locate severe weather
• Most information comes from the National Weather Service
– They use balloons, satellites, radar, and surface instruments to gather weather data
Weather Technology
• Techniques for predicting weather have changed dramatically in recent years
• Short-range forecasts—forecast for up to five days—are now fairly reliable
• Meteorologists can also make somewhat accurate long range predictions
• Technological improvements in gathering weather data and using computers have improved the accuracy of weather forecasts
Weather Balloons
• Carry instruments high into the troposphere and lower stratosphere
• Measure temperature, air pressure, and humidity
Weather Satellites
• Orbit Earth in the exosphere
• Makes images of Earth’s surface, clouds, storms, and snow cover
• Data on temperature, humidity, solar radiation, wind speed and wind direction, and provide images of clouds and storm systems
Modeling Weather Satellites
• Geostationary satellites orbits Earth from west to east—remain above the same spot on Earth’s surface
• 35,800 km
• Polar satellites orbit Earth from north to south—fly over the poles twice each day
• 850 km
Automated Weather Stations
• Surface locations for temperature, air pressure, relative humidity, rainfall, and wind speed and direction
• NWS has established a network of over 1,700 sites
Computer Forecasts
• Gather large amounts of information including temperature, humidity, air pressure, wind…etc.
• Processes quickly to help make predictions
• Works through thousands of calculations using equations from weather models
• New data comes in—the computer will revise