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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