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Weather Forecasting
Science 10
Weather
• Humans have long been interested in weather
forecasting, the process of predicting future
weather based on ongoing observations of
atmospheric conditions.
• Even before we had the technology of weather
instruments, humans were forecasting weather
based on the behavior of plants and animals,
characteristics of the Sun and moon, and cloud
formations. We often refer to these as weather
folklore
Measuring Weather Data
• Meteorologists measure the components of
weather using a variety of instruments and
observation systems.
Weather Component
Instrument
Units
Temperature
Thermometer
°C
Wind speed
Anemometer
Km/h
Wind direction
Wind vane
Humidity
Hygrometer
Compass direction
(NW)
%
Air pressure
Barometer
kPa
Precipitation
Rain gauge or meter
stick
mm and cm
Humidex
• Humidity can drastically affect temperatures or
what we refer to as “feels like” temperature.
Environment Canada created what is known as the
humidex scale.
• It takes into account the temperature along with
the humidity and tells us how we will feel on a hot
day when the humidity is high.
• For example, on a day where it is 30°C and the
humidity is 95%, the “feels like” temperature will
be 47°C. This is because the humidity in the air
prevents the sweat on our skin from evaporating
and we cannot cool down.
Beaufort Wind Scale
• Before anemometers,
humans used what is
known as the Beaufort
wind scale to describe and
determine wind speed.
• It is a scale from 0-12 that
describes wind based on
the behavior of the ocean
and objects on land. See
Table 2.1 on page 53 in
your text to explore the
descriptions on the scale.
Weather Observation Systems
• Along with weather instruments,
meteorologists also use weather observations
systems to collect weather data. They are
collectively known as remote sensing
technology (RST) because they can collect
data without being in physical contact with
the object being observed. These include
weather balloons, weather radar and
weather satellites.
Weather Balloons
• Meteorologists send
weather balloons
containing a radiosonde
into the atmosphere to
collect weather data.
• It can collect data on
temperature, atmospheric
pressure, humidity, along
with wind speed and
direction.
• Eventually the balloon will
burst and the radiosonde
will parachute back to
Earth.
Weather Radar
• This is a very important
form of remote sensing
technology. It sends out
radio waves that reflect
off objects in the
atmosphere and its main
function is to detect
precipitation and storms.
• The higher the amounts
of precipitation present
in the clouds, the greater
the amount of reflection.
Weather Radar
• Special radar technology
known as Doppler radar
can determine the
direction and speed of
weather systems, which
allow us to predict the
behavior of approaching
storms.
• To see the image created
by radar, go to page 55 in
your textbook and look at
figure 2.16.
Weather Satellites
• This remote sensing technology has been launched
into orbit around the Earth and they monitor the
behavior of the atmosphere and help us predict and
understand the development and movement of
weather systems (i.e., fronts, high pressure & low
pressure systems).
• They use technology such as infrared and visible
light sensors and can determine cloud height and
the difference between types of precipitation.
• We currently use two types of weather satellites,
Geostationary and Polar Operating Environmental
Satellites.
Geostationary Operating
Environmental Satellites
• GOES orbit the Earth
about 36000 km above
the equator, travels at
the same speed as the
Earth rotates and
therefore monitors a
fixed location.
Polar Operating Environmental
Satellites
• POES orbit the Earth 14
times per day collecting
data from the entire
globe. POES collect
data that allow us to
track various weather
systems.
Forecasting the Weather
• Meteorologists can use collected weather data
to make short-range forecasts (48hrs) and
long-range forecasts (3-7 days). Short range is
based on what is known as persistence
forecasting. In other words, the assumption
that current weather patterns will continue for
a few hours. Meteorologists also use
nowcasting, which uses data from RST and
forecasts weather for up to 6 hours.
Weather Symbols
• When data is recorded and forecasts are being
made, meteorologists use a variety of weather
symbols, which are displayed on maps to indicate
weather conditions. Refer to page 63 in your text to
explore some common weather map symbols.
• Due to the fact that weather maps show current
conditions, they can be used for short term
forecasting. They can look for patterns and trends
and make predictions on how the atmosphere will
behave. They watch for systems meeting one
another, locations of weather fronts, speed and
direction of systems and all this combines to make
a weather forecast.
Long-range Forecasting
• Long-range weather forecasting is much more
difficult and relies on statistical analysis of
past weather data and computer models of
atmospheric circulation and behavior.
• These forecast are often unreliable because
the computers are making assumptions about
how the atmosphere will behave but it is one
of the most unpredictable systems on earth!
Importance and Limitations of
Weather Forecasting
• Weather forecasting is very important to help
people prepare for a variety of weather
conditions, some of which can be hazardous to
our health, others that can cause unsafe driving
conditions, and some that can cause major
property damage.
• A forecast helps us to make choices daily based
on weather conditions. It can be as simple as
what clothing to wear or as complicated as
stocking up on food and supplies to prepare for
extreme weather.
Importance and Limitations of
Weather Forecasting
• Weather forecasting can
help us prevent loss of
life, property damage
and even helps us
prevent weather
related illnesses such a
hyperthermia.
Effects of Weather on Agriculture
• There are many, many ways that weather can
affect agriculture. It can be a very dry or
overly wet season, and early or late frost or a
heavy hailstorm that destroys crops meant for
human consumption. Animals may not
survive overly cold or hot seasons. Accurate
predictions of weather can help farmers
prepare for these impacts and time their
planting, protection and harvesting of crops.
Effects of Weather on Marine
Industries
• Fishermen and offshore oil workers risk injury
and death out on the ocean daily, due largely
in part to weather. Good and reliable weather
forecasting is needed to help them make key
decisions about when to go out on the ocean
and when they need to come ashore.
Effects of Weather on the Forestry
Industry
• Almost half of the 9000 forest fires each year
in Canada are started by lightning strikes.
Accurate weather forecasting can help us
prepare for the possibility of forest fires and
prevent millions of dollars in damage , not to
mention the cost to ecosystems, wildlife and
the atmosphere will all the excess carbon
dioxide that is released.
Effects of Weather on Transportation
• Weather forecasts are essential to help people
prepare for travel, whether it is on roads, over
the water or in the air. Bad driving conditions
cost us over $1 billion in damage each year to
vehicles and infrastructure. Many flights are
cancelled or delayed due to weather
conditions in an attempt to eliminate risk to
flight crews and passengers.
Limitations of Forecasting
• The need and importance of weather forecasting is
obvious, however we are still limited in what we can
predict. We have minimal control over weather and
ultimately the atmosphere is too unpredictable to
ever know with 100% accuracy what is going to
happen.
• The good news is that with our improved technology,
our current 5-day predictions are as accurate as our
2 day predictions were 20 years ago.