Transcript Extreme Weather

Weather
Extreme Weather
Summary
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Thunderstorms
Tornadoes
Floods
Droughts
Hurricanes, Typhoons & Tropical
Cyclones
 Blizzards
Thunderstorms
 Has lightning, thunder, heavy rain and
sometimes hail
 Need two conditions:
 Moisture to form clouds and precipitation
 Strong lifting of air to make clouds that reach
high in the atmosphere.
Thunderstorms Cont’d
 Low temperature at high altitude creates
a large temperature difference with the
warm air that is lower.
 The warm air rises quickly because of
this temperature difference.
 Water vapour rises and hits the cold air
where it condenses making clouds.
 Once the clouds are heavy enough rain
falls in the downdrafts.
Thunderstorms cont’d
 Thunderstorm clouds can reach higher
than airplanes travel so pilots must
maneuver around them.
 As the thunderstorm reaches its end the
flow of air becomes mostly downward.
Tornadoes
 Because of their extremely high winds
tornadoes can cause more damage in a
short time than any other storm on Earth.
 Tornadoes are a severe component of a
thunderstorm.
 It is very difficult to predict their path or
even exactly where they are going to
occur.
Tornadoes cont’d
 Fast rising air in a thunderstorm
sometimes begins to spin forming a
funnel of air and moisture.
 Rising air is replaced by cooler air which
increases rotation.
 The funnel cloud produces a pressure
difference that can pick objects up.
 Wind speed can be as high as 500 km/h.
Floods
 Excess of water when the land can’t soak
up any more water.
 Can’t happen in Antarctica. Why not?
 Two types of floods:
 Flash
 Broadside
Flash Floods
 Little or no warning.
 Can happen in cities if the water can’t
drain fast enough.
 Happens more when mountain valleys or
gorges can’t accommodate spring rain
and melting snow.
 Can also occur when a dam bursts or
overflows
Broadside Floods
 Can cover large areas of land for months.
 Can be predicted days or weeks before.
 Causes:
 Rivers flood from mountain snow melting.
 Winter of heavy snowfall followed by rainy
spring.
 More rain than normal so soil becomes
saturated.
 Tropical storms bring lots of rain.
Droughts
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No precipitation for a long time.
Can cause wildfires.
Can last for long periods of time.
Sometimes places flood from lots of rain
at one time and then have a drought
later.
Hurricanes, Typhoons and
Tropical Cyclones
 Same type of storm just located in different
places of the world.
 Has to be near the equator where the water
surface temperature is high enough (about 27ºC)
 Happen when cyclones become large enough.
 If wind speed is 63km/h its called a tropical
storm; if wind speed is 119km/h its called a
hurricane.
 Typhoons and tropical cyclones can be worse
than hurricanes.
 Hurricane: western Atlantic Ocean,
Caribbean Sea, Gulf of Mexico or eastern
Pacific Ocean
 Typhoon: northwestern Pacific Ocean or
China Sea
 Tropical Cyclone: Australia area or Indian
Ocean
Hurricane Development
 Warm air above warm water rises quickly
carrying moisture with it.
 As this air reaches higher altitude the
water vapour condenses releasing heat
and increasing speed of rising air.
 Rising air creates a low pressure area
that cool dry air moves into.
 Cool air at the top also swirls outward
and back down to be warmed again.
Hurricanes cont’d
 The core of the hurricane is called the
eye.
 The eye is the low pressure area that is
calm with clear skies.
 Hurricanes can carry lots of rainfall inland
creating floods and destruction.
Blizzards
 Severe snow storm with strong winds
and low temperatures.
 Winds must exceed 55km/h and visibility
must be less than 0.5km.
 Blizzards develop similarly to
thunderstorms but with snow because of
the cold temperatures.
 What are some dangers of blizzards?