Transcript Y10Ge UA3.3 Storms Nov23_4PP

More Hazards
Tropical storms
Tropical storms have names in different
places
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Here is a hurricane
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Look at these to get the idea of how
they form
• http://www.ucar.edu/news/features/hurri
canes/inside_the_storm.html
• And
• http://news.bbc.co.uk/1/hi/sci/tech/4588
149.stm
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• Hurricanes all start over the sea where, for reasons
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that we do not fully understand, a patch of ocean has a
surface temperature of more than 260C.
This generally happens between 50 and 200 of latitude.
The hot air rises taking a lot of water vapour with it. As
the water vapour rises up it cools to form big cumulus
clouds. This creates very low pressure at sea level.
Wherever you have low pressure, air with higher
pressure tends to move in to replace it.
The winds that travel around the Earth (called the
Trade Winds) at this point are pulled in to fill the gap
left by the rising air. But due to the turning effect of
the earth, air does not move straight into a low pressure
zone but whirls in around and towards it – just like the
water going down the plug hole – for the same reason.
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• We have the hot air rising, the air coming in from
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outside and coming under the cloud in a spin, picking up
more water vapour and spiralling upwards as it warms.
This has 2 effects; the first is that the storm clouds
begin to be pulled into a spin by the incoming wind. The
second effect is that the spinning storm is pulled
outward – leaving a low pressure funnel at the centre.
Now way up high there is cold air which is under higher
pressure so this is sinks down into the centre – at the
bottom this begins to warm and gets pulled in to the
warm spinning stormy mass, and so more cold air follows
in after it.
As everything is spinning faster and faster the storm
begins to drift sideways because of the trade winds – in
a westerly direction and away from the equator. So in
the Northern Hemisphere this is NW.
What is it the Southern hemisphere?
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• Not only that but this huge bundle of energy depresses
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the sea level under it, so there is a backup ridge of
water all around it – this gives rise to surges both
before and after the hurricane has passed.
Provided they have available warm water and there is no
wind high in the atmosphere, they will gather speed as
they move.
So the hurricane brings surges and high winds and heavy
rain all together! This why they cause so many problems
to the countries they cross.
But once they meet landfall, the warmth from the warm
water is no longer available and so the winds quickly slow
down they pass over the coast. Also the very low
pressure at their centre begins to rise, as the air is not
ascending so fast. There will still be heavy rain clouds in
the system but the devastating damage of high winds in
excess of 120km per hour is less of the problem.
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This is typical of what happens
• Note the direction of
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spin of the hurricane –
this is in the northern
hemisphere.
Notice the variation in
wind speeds – this too
is typical.
Notice where the
storm surge has most
impact – why do you
think that is?
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So what is a category 1 Hurricanes like?
• 119-153 km winds
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internally.
Storm surge 1.2 – 1.5m
Minimal Damage on land
Broken tree branches.
Damage to trailers and
mobile homes.
Bent and broken signs.
Some small boats torn
away from their docks.
Photo of a damaged
McDonald's Restaurant
sign. Large pieces are
missing from both the
main sign section and
the golden arches
above.
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So what is a category 2 Hurricanes
like?
154–177 km winds internally.
Storm surge 1.8 – 2.4m
Moderate Damage
Heavy damage to trees; some
trees knocked down.
Major damage to trailers and
mobile homes.
Some damage to roofs,
windows, and doors.
Heavy damage to piers and
marinas.
Many small boats torn away
from their dock
Photo of an overturned
mobile home resting
against the trunks of
several damaged and
downed pine trees.
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So what is a category 3 Hurricanes
like?
178–209 km winds internally.
Storm surge 2.7–3.7m
Extensive Damage
Large trees knocked down.
Some mobile homes
destroyed.
Damage to roofs, windows,
doors, and small buildings.
Smaller buildings near the
shore destroyed.
Large buildings next to shore
damaged by waves.
Flooding near coast.
Photo showing a large
section of a beach-front
hotel that has lost its
foundation and totters
toward the sea.
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So what is a category 4 Hurricanes
like?
210–249 km winds internally.
Storm surge 4.0–5.5 m
Extreme Damage
All signs knocked down.
Severe damage to houses.
Mobile homes completely
destroyed.
Major damage to buildings
near shore.
Widespread flooding.
Major beach erosion.
Photo showing a residential
neighbourhood that has
been heavily damaged by
hurricane-spawned
tornados. Some houses are
completely demolished,
while sections of bare walls
remain standing where other
houses used to be. Debris
litters the yards and streets.
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So what is a category 5 Hurricanes like?
• >250km/hour km winds
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internally.
Storm surge > 5.5 m
Catastrophic Damage
Completely destroyed
roofs on many buildings.
Some buildings completely
destroyed.
Small buildings turned
over or blown away.
Very severe damage to all
buildings near the shore.
Two photos showing an apartment
building before and after it was
completely demolished by the
storm surge of Hurricane Camille.
The before picture shows three
buildings with a lawn, trees, and
parking lot. The after picture shows
only rubble where the building
stood and bare trees.
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What we have been talking about is the
effects of hurricanes, typhoons or
cyclones
• Let’s look at a category 1 storm:
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119-153 km winds internally.
Put these in the
Storm surge 1.2 – 1.5m
impacts box in any
Minimal Damage on land
order with a (L) or
(S) after each one
Broken tree branches.
Damage to trailers and mobile homes.
Bent and broken signs.
Some small boats torn away from their docks.
• These lead to some short term and maybe a few long
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term impacts on humans as a result of the storms.
What might the short term impacts be? Can you think of
any long term ones?
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What we have been talking about is the
effects of hurricanes, typhoons or
cyclones
• Let’s look at a category 2 storm:
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154–177 km winds internally.
Storm surge 1.8 – 2.4m
Moderate Damage
Heavy damage to trees; some trees knocked down.
Major damage to trailers and mobile homes.
Some damage to roofs, windows, and doors.
Heavy damage to piers and marinas.
Many small boats torn away from their dock
• These effects could lead to some more short term and
additional long term impacts on humans as a result of the
storms. What do you think?
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What we have been talking about is the
effects of hurricanes, typhoons or
cyclones
• Let’s look at a category 3 storm:

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178–209 km winds internally.
Storm surge 2.7–3.7m
Extensive Damage
Large trees knocked down.
Some mobile homes destroyed.
Damage to roofs, windows, doors, and small buildings.
Smaller buildings near the shore destroyed.
Large buildings next to shore damaged by waves.
Flooding near coast.
• These effects could lead to some more short term and
additional long term impacts on humans as a result of the
storms. What do you think?
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What we have been talking about is the
effects of hurricanes, typhoons or
cyclones
• Let’s look at a category 4 storm:


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
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210–249 km winds internally.
Storm surge 4.0–5.5 m
Extreme Damage
All signs knocked down.
Severe damage to houses.
Mobile homes completely destroyed.
Major damage to buildings near shore.
Widespread flooding.
Major beach erosion.
• These effects could lead to some more short term and
additional long term impacts on humans as a result of the
storms. What do you think?
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What we have been talking about is the
effects of hurricanes, typhoons or
cyclones
• Let’s look at a category 5 storm:



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>250km/hour km winds internally.
Storm surge > 5.5 m
Catastrophic Damage
Completely destroyed roofs on many buildings.
Some buildings completely destroyed.
Small buildings turned over or blown away.
Very severe damage to all buildings near the shore.
• These effects could lead to some more short
term and additional long term impacts on humans
as a result of the storms. What do you think?
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So now have looked at some of the
possible impacts
• Same hurricane –
different places?
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Same natural forces affect different
areas in a variety of ways
• Now, we are going to think about how
those impacts vary between LICs and
HICs.
• For homework you are going to find out
about the impact of a couple of recent
hurricanes – one from an LIC and one from
an HIC to see if our ideas support what
really happens.
• To the whiteboard for the ideas we
collected.
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