Transcript Forecasting the weather

Forecasting the weather
Weather: The state of the atmosphere at a
specific time and place.
Meteorologist: scientists who study the
atmosphere
Weather forecasts are issued:
– to save lives
– reduce property damage
– reduce crop damage
– to let the general public know what to expect
How far ahead can meteorologists
accurately predict the weather?
• 0-12 hrs: pretty accurate except for
unpredictable local storms.
• 12-48 hrs: are able to predict which areas
will be hit by severe storms.
• 3-5 days: big events or storms can be
predicted (hurricanes, floods).
• 6-10 days: can give an average temp for a
period of time.
How do they do it?
• Meteorologists look at:
– Existing weather conditions over a large area.
– Current data gathered from:
• Satellite images
• Weather stations
• Weather balloons
– This data includes:
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Three important
factors that shape
the weather in a
given region are:
— temperature
Atmospheric pressure
— pressure
Wind direction and speed
— water
Temperature of the air
Humidity, clouds, and precipitation
Making a weather map
• The basic tool of a weather forecaster is the
WEATHER MAP.
• The weather map shows the:
– distribution patterns of atmospheric pressure
– wind
– temperature and humidity
at the different levels of
the atmosphere.
Low and High Pressure Systems
• When a cold front moves into
a region and warm air is
forced upward, an area of low
pressure is created near
Earth’s surface.
• A center of high pressure
tends to be found where a
stable cold air mass has
settled in a region.
Remember: Wind is a horizontal movement of air from
a area of high pressure to an area of low pressure.
Isobars
• Curved lines that indicate areas of equal air
pressure.
• Indicate wind speed and wind direction
Iso = equal bar = pressure
Closely spaced lines=
high change in pressure +
high wind speed.
Widely spaced lines=
slow change in pressure +
low wind speed.
High pressure system
(depicted by an "H")
Low pressure system
(depicted by an "L”
Wind
• Winds are identified as the direction FROM
which they come.
From which direction is
the wind coming
according to this wind feather?
Weather Symbols
fog
haze
,
rain
snow
* slight rain
thunderstorm
drizzle
lightning
showers
.
ice or snow
pellets
cloud development
not observed
no clouds
about 60%
about 10%
about 75%
about 25%
about 80%
about 40%
completely
overcast
about 50%
sky
obscured