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.

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

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 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

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

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