Transcript Predicting Weather

Before you decide to do outdoor activities, it is important
that you know what kind of weather it will be. If you look out
and the sky is sunny without any clouds, you might predict,
or be able to tell beforehand, what the weather will be like
for the next hour. However, just a look in the sky won’t tell
you what is in store for the next few days.
Meteorologists are the people who study weather. They
predict what the weather will be like for the next few days.
Before they can predict they have to collect information.
We have learned how to measure temperature, air pressure,
precipitation, wind speed and direction, and humidity. Meteorologists collect this same information from many places, not just
one. They know that the weather in other places influences the
weather where we are.
Many meteorologists get this information from the National
Weather Service. This is a government agency that has weather
stations collecting information from all over the U.S.
Weather balloons, radar, and satellites are three tools that
collect information. Weather balloons collect information from
high in the air.
Radar sends radio waves into the air. They bounce
off of rain and snow. Radar is used to find where precipitation
is and where it is moving.
Satellites high above the earth’s air collect and send
information about the weather all over the world.
Meteorologists need information about air masses to
predict weather. An air mass is a large amount of air that has
the same temperature and humidity. It can be warm or cold.
It can have a large amount of water vapor or a small amount.
Air masses are so large that two or three different air masses
can cover most of the U.S.
Meteorologists also need information about fronts to predict
the weather. A front is the line where two air masses meet.
The air masses do not mix together but stay separate.
A cold air mass often causes thunderstorms. Clouds from a warm
air mass often cause a steady rain.
Meteorologists use information about the weather to predict
what the weather is going to be like. This prediction is called
a forecast.
One way they predict weather is to look at the weather in
the west. Air masses that cause weather usually move from
west to east.
Meteorologists know the kinds of weather that often happen
with certain air pressures, air masses, and fronts. High pressure
areas often have fair weather. Low pressure areas often have
clouds and precipitation.
A warm air mass that comes from over the Gulf of
Mexico might bring hot, humid weather on a summer day.
A cold air mass from over Canada might bring cooler
weather. Thunderstorms and snowstorms often happen
at a cold front. Steady rain or snow often happen at a
warm front.
Meteorologists study the direction air masses are moving.
They study where high pressure areas and low pressure areas
are moving. They try to predict what air mass, front, and air
pressure are moving into your area. Then they predict what
the temperature, chance of precipitation, and wind might
be.