24.6 Predicting the Weather
Moonlight reflecting
off ice crystals in
cirrostratus clouds
can cause a halo to
appear around the
moon.
Such a halo often
indicates that
precipitation is on
the way.
24.6 Predicting the Weather
Weather Forecasting
What technologies help meteorologists
predict the weather?
Meteorologists are scientists who study
weather.
Meteorologists use many technologies to
help predict the weather, including Doppler
radar, automated weather stations, weather
satellites, and high-speed computers.
24.6 Predicting the Weather
Weather Forecasting
Doppler Radar
Doppler radar is a technology based on use of the
Doppler effect.
• Doppler radar bounces radio waves off particles of
precipitation and measures the frequency of the
returning waves.
• The speed of the storm can be calculated from how
much the frequency changes, so meteorologists can
track the paths of thunderstorms and potential
tornadoes.
24.6 Predicting the Weather
Weather Forecasting
Weather Stations and Satellites
Automated weather stations gather information
without a human observer being present.
A typical weather station includes sensors that
measure temperature, precipitation, and wind
speed and direction.
The information collected is transmitted as radio
signals to a weather center.
24.6 Predicting the Weather
Weather Forecasting
These scientists are
setting up an automatic
weather station on an
island in the Bigourdan
Fjord, Antarctica.
24.6 Predicting the Weather
Weather Forecasting
Weather satellites orbit Earth to collect
information about weather, including cloud
cover, humidity, temperature, and wind speed.
Meteorologists combine data from various
weather stations and satellites to form a
comprehensive view of a region’s weather.
24.6 Predicting the Weather
Tracking the Weather
Meteorologists track weather data closely to
help produce accurate short-term forecasts
and to understand longer-term variations in
weather. The table provides the actual daily
average temperature and daily precipitation
for Minneapolis and St. Paul, Minnesota, for a
seven-day period. Use the table and your
knowledge of weather to answer the
questions.
24.6 Predicting the Weather
Tracking the Weather
1. Using Tables On which day was the average
daily temperature highest? On which day was it
lowest?
Answer:
24.6 Predicting the Weather
Tracking the Weather
1. Using Tables On which day was the average
daily temperature highest? On which day was it
lowest?
Answer: Day 3 and Day 4; Day 7
24.6 Predicting the Weather
Tracking the Weather
2. Calculating The average daily temperature on
Day 7 was 11°C below normal. What is the normal
temperature for that date?
Answer:
24.6 Predicting the Weather
Tracking the Weather
2. Calculating The average daily temperature on
Day 7 was 11°C below normal. What is the normal
temperature for that date?
Answer: –2°C
24.6 Predicting the Weather
Tracking the Weather
3. Using Tables What were the maximum and
minimum average daily temperatures over the
week? What was the temperature range?
Answer:
24.6 Predicting the Weather
Tracking the Weather
3. Using Tables What were the maximum and
minimum average daily temperatures over the
week? What was the temperature range?
Answer: Maximum was –4°C; minimum was –13°C;
range was 9°C.
24.6 Predicting the Weather
Tracking the Weather
4. Inferring What was the total precipitation over the
seven days? What was the likely form of this
precipitation?
(Hint: Recall that the freezing point of water is 0°C.)
Answer:
24.6 Predicting the Weather
Tracking the Weather
4. Inferring What was the total precipitation over the
seven days? What was the likely form of this
precipitation?
(Hint: Recall that the freezing point of water is 0°C.)
Answer: 34 cm; snow
24.6 Predicting the Weather
Tracking the Weather
5. Predicting What type of front most likely passed through
the region on Day 6 or Day 7? Predict the weather conditions
that followed.
Answer:
24.6 Predicting the Weather
Tracking the Weather
5. Predicting What type of front most likely passed through
the region on Day 6 or Day 7? Predict the weather conditions
that followed.
Answer: A cold front passed through, as seen from the heavy
snow on Day 6 and the significant drop in temperature on
Day 7. Cold temperatures and clear skies follow cold fronts.
24.6 Predicting the Weather
Tracking the Weather
6. Making Generalizations Suppose you were visiting
Minneapolis during this period. Describe how the weather
changed during your visit.
Answer:
24.6 Predicting the Weather
Tracking the Weather
6. Making Generalizations Suppose you were visiting
Minneapolis during this period. Describe how the weather
changed during your visit.
Answer: A week of chilly weather, with temperatures
becoming even colder on Day 7. Two days of heavy snow
and light snow on three other days.
24.6 Predicting the Weather
Weather Forecasting
High-Speed Computers
High-speed computers help meteorologists
compile and analyze the tremendous amount of
weather data collected every day. With these data,
scientists make forecasts.
• Most forecasts can be quite accurate from 12 hours
to 3 days.
• Meteorologists can also accurately forecast the
movement of large weather systems over a period of
3 to 7 days.
• Predicting beyond a week is extremely difficult.
24.6 Predicting the Weather
Weather Forecasting
Meteorologists use computers to help
forecast the weather.
24.6 Predicting the Weather
Weather Maps
How do meteorologists show information on
weather maps?
Weather maps typically show predicted
temperatures and include sun or cloud
symbols to indicate cloud cover. They have
drawings of rain or snow to show areas of
precipitation.
24.6 Predicting the Weather
Weather Maps
To help analyze weather data, meteorologists
make maps that show weather patterns of
different regions and symbols for the different
kinds of fronts and areas of high and low
pressure.
24.6 Predicting the Weather
Weather Maps
A comprehensive weather map typically
includes information about weather systems
and fronts.
• Isotherms are lines that connect points of equal
air temperature.
• An isobar is a line that connects points of equal
air pressure.
24.6 Predicting the Weather
Weather Maps
The isobars on this weather map encircle the
centers of low-pressure and high-pressure
systems.
24.6 Predicting the Weather
Assessment Questions
1. Which technology is used to measure the motion
of storms?
a.
b.
c.
d.
Doppler radar
automated weather stations
computers
barometer
24.6 Predicting the Weather
Assessment Questions
1. Which technology is used to measure the motion
of storms?
a.
b.
c.
d.
Doppler radar
automated weather stations
computers
barometer
ANS: A