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