1. 20.5 Forecasting Weather Objectives
Compare and contrast the different technologies used to gather weather data.
Analyze weather symbols, station models, and weather maps.
Describe how weather forecasts are made.

2. Introduction
Forecasting weather is a complex process that requires the cooperation of countries around the world
Gather weather information for their regions
Send this information too computer centers
Compile information and use it to create weather maps and forecasts
Local forecasters modify the forecasts to reflect local conditions

3. Gathering Data
Huge amounts of data are necessary for weather forecasting
Satellites
Instruments attached to balloons
Weather stations
Weather radar
Airplanes
Ships

4. Satellites Provide weather information about every spot on Earth
2 basic types of satellite images
Visible
Infrared

5. 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

6. 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

7. 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

8. 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

9. Radiosondes Instrument package attached to a balloon
Carries it up into the atmosphere
Transmits weather information to computers on the ground

10. 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

11. 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

12. Surface Observations (cont’d)
Most weather stations are at airports
Can easily retrieve data from commercial jets with automatic weather recorders

13. 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

14. 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

15. 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

16. Making a Surface Weather Map
Steps to make a surface map
Computer draws a map showing station models
Draws isobars every 4 millibars and identifies highs and lows
Forecasters draw in the fronts
A) 3 types of data from the station model to find fronts
Temperature
Wind direction
Dew point

17. Making a Surface Weather Map (cont’d)
Rules to locate fronts
Wind direction changes behind front
Temperature changes sharply across fronts
Dew point changes sharply across fronts

18. 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

19. Forecasting (cont’d) Models begin with observed current weather data
Temperature
Humidity
Wind at various levels of the atmosphere

20. 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

21. Forecasting (cont’d)
Different models may produce different predictions
Meteorologists decide which model to use as a basis for a forecast

22. 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

23. 20.5 Review
Kahoot
Exit Ticket
Activity
Forecasting weather