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20.5Forecasting Weather
Objectives1) Compare and contrast the different
technologies used to gather weather data.
2) Analyze weather symbols, station models, and weather maps.
3) Describe how weather forecasts are made.
Introduction Forecasting weather is a
complex process that requires the cooperation of countries around the world
1) Gather weather information for their regions
2) Send this information too computer centers
3) Compile information and use it to create weather maps and forecasts
4) Local forecasters modify the forecasts to reflect local conditions
Gathering Data
Huge amounts of data are necessary for weather forecasting
Satellites Instruments attached to
balloons Weather stations Weather radar Airplanes Ships
Satellites
Provide weather information about every spot on Earth
2 basic types of satellite images
Visible Infrared
Visible Satellite Images
Uses light to create images
Black-and-white picture of Earth
White = sunlight reflected off clouds or snow cover
Brighter the white = thicker the clouds
Gray = land Black = water
Visible Satellite Images (cont’d)
Can Estimate wind speed
and direction Track storms Estimate the stage and
severity of hurricanes Aren’t available at
night
Infrared Satellite Imagery
Uses temperature to create pictures
Can be taken day or night
Bright areas represent cold temperatures
Darker areas are warmer
Represent lower clouds Lack or clouds
Infrared Satellite Imagery (cont’d)
Temperatures of cloud tops to determine how tall the clouds are
Taller the cumulus clouds = more severe the thunderstorms produced
Estimate wind speed and direction at different altitudes
Provide images of water vapor in the air
Determine temperature and humidity at different altitudes
Radiosondes Instrument package
attached to a balloon
Carries it up into the atmosphere
Transmits weather information to computers on the ground
Radiosondes (cont’d)
Measure the temperature, pressure, and humidity of air at different altitudes
Estimate air stability and the likelihood that cumulus clouds and thunderstorms will develop
Maps show the shape and intensity of the jet stream Important in determining the movement of air masses and
storms
Surface Observations
Only by analyzing data from weather stations can meteorologists diagnose
Where in a storm it is Raining Snowing Where fronts and lows
are located
Surface Observations (cont’d)
Most weather stations are at airports
Can easily retrieve data from commercial jets with automatic weather recorders
Surface Observations (cont’d)
Information on conditions over the oceans comes from ships and from automated stations on moored buoys
Weather stations typically report conditions every hour
Temperature Dew point Barometric pressure Wind speed and direction Visibility Precipitation Height of clouds Amount of cloud cover
Station Model
Station model: Includes information on temperature, dew point, weather conditions, wind speed and direction, barometric pressure, and cloud cover
Can be read by the meteorologists of any country
Making a Surface Weather Map
Essential tools that give weather forecasters the “big picture” of current weather conditions
Made every 3 hours by the National Center for Environmental Prediction (NCEP)
Silver Spring, Maryland
Making a Surface Weather Map
Steps to make a surface map1) Computer draws a map
showing station models2) Draws isobars every 4
millibars and identifies highs and lows
3) Forecasters draw in the fronts
A) 3 types of data from the station model to find fronts
1) Temperature2) Wind direction3) Dew point
Making a Surface Weather Map (cont’d)
Rules to locate fronts1) Wind direction changes
behind front2) Temperature changes
sharply across fronts3) Dew point changes
sharply across fronts
Forecasting Modern-day weather
forecasts Based on computer
weather models Large computer programs
containing mathematical equations designed to simulate atmospheric processes
Many different models are used to make forecasts
Some are used to predict the weather up to 2 days in advance Run 4 times per day
Provide info up to 10 days in advance
Forecasting (cont’d) Models begin with observed current weather data
Temperature Humidity Wind at various levels of the atmosphere
Forecasting (cont’d)
Transfer data into mathematical equations and predict future state of the atmosphere
Temperatures Winds Sea-level pressure Precipitation Configurations of the jet
stream
Forecasting (cont’d)
Different models may produce different predictions
Meteorologists decide which model to use as a basis for a forecast
Forecasting (cont’d)
Subtle factors not included in the models can have a large impact on the weather Urbanization
Plays a large role in the intensity of heat waves Local effects
Too subtle for models to predict Forecasters use their knowledge of local weather patterns to modify the predictions they
receive from models
20.5 Review
Kahoot Exit Ticket Activity
Forecasting weather