Extreme Weather Complete Revision Guide (with case studies)

I have made this revision booklet for the Edexcel extreme weather section of the geographical investigations paper

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Extreme Weather Revision Booklet
Extreme Weather Watch
Extreme weather is weather that's unusually severe or that
occurs in an area where it's unexpected.
There are many types of extreme weather temperate storms,
tornadoes tropical cyclones, heatwaves, droughts,
blizzards and ice storms.
Temperate storms are caused by depressions
Temperate storms are weather systems with strong winds and
heavy rainfall. They're caused by extreme low pressure
systems called depressions. This is how one forms:
1. Warm air constantly moves out of tropical areas, towards the
poles. A warm front is the leading edge of a warm air mass.
2. Cold air move out of the polar regions, towards the tropics. A
cold front is the leading edge of a cold air mass.
3. Where the air masses meet (in the temperate zone) the warm
air heading towards the poles rises above the cold air heading
towards the tropics (because warm air is less dense than cool
4. The rising warm air means there is less air at ground level, so
atmospheric pressure is reduced (measured with a Barmometer)
5. Strong winds blow into this low pressure area in a spiral fashion.
6. The direction of these winds combined with the fact that cold
fronts move more quickly than warm fronts leads to the cold
front catching up the warm front
7. When this happens the warm air behind the warm front is
undercut by the incoming cold front and is lifted away from the
ground entirely. It now sits above the cold air this is an occluded
front. The warm air rises into the upper atmosphere and the
depression dissipates.

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Depressions have many hazards such as:
Floods from continuous rain
Gales from high winds (storms)
Blizzards from snow
Storm surges at coast
Anticyclones are areas of high pressure. They bring calm
weather and may last from a few days to weeks (bringing hot
sunny weather to the UK for example). Because the air is
subsiding (sinking) there is little change of precipitation as the air
warms as it descends. Isobars are widely spaces and the air
circulates in a clockwise direction.…read more

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What's Behind UK Weather
Traditional View: When air from the Atlantic moves over
England, it meets with cooler denser air, which means it rises,
condenses and forms precipitation. At other times, continental air
is producing high pressure anticyclones, which bring stable
Modern Insight: The Polar jet stream (10 km in the air)
determine the pattern of high and low surface pressure.
Meteorologists suggest the conditions oscillate between two
Blocked Phase: Westerlies are blocked by anticyclonic
systems over Europe ('Blocking Highs').…read more

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Tornados and Supercell Storms
A tornado is a violently rotating column of air (vortex). They come from the
cloud and make contact with the ground. The majority only make landfall for
a very short amount of time and cause little damage.
They have the power to lift 20 tonne rail carts. They move at 62 mph, but
have been recorded at moving up to 70 mph.…read more

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With regards to the distribution of tornados, there is no pattern of
number, damage etc (no correlation with climate change)
Tornados tend to occur during the late afternoon and into the
evening, because the sun has been heating the ground all day.…read more

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Hurricanes and Tropical Storms
A hurricane is a tropical storm with sustained wind speeds in excess of 120
km/h which originates in the tropics
The Inter Tropical Convergence Zone (ITCZ) is a zone of low pressure near
the equator. This migrates seasonally, creating conditions that favour hurricane
formation and monsoon winds.
They affect over 80% of the Earth's landmass.…read more

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It was the most costliest and fifth most deadliest hurricane in US history.
It was the 6th strongest Atlantic hurricane recorded.
Hurricane Katrina formed over the Bahamas on August 23 2005, and crossed
southern Florida as a moderate category 1 hurricane, causing some deaths and
flooding before strengthening rapidly in the gulf of Mexico. The storm weakened
before making landfall as a category 3 storm on the morning of monday 29th
August in southeast Louisiana.…read more

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Super Typhoon Bopha December 2012
It was the strongest tropical cyclone to ever hit the Philippines
south island of Mindanao, making landfall as a category 5 super
typhoon with winds exceeding 160 mph, making landfall on the
3rd of December 2012
Affected over 213,000 people.
More than 179,000 people in evacuation shelters
A death tole of over 1,000 people, with over 800 still
missing (mainly fishermen)
$1.…read more

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Blizzards and Ice Storms
A snowstorm become a blizzard when wind speeds exceed 35 mph (wind
speeds measured with a digital anemometer) Temperatures in these conditions
can drop to 12 degrees and visibility is poor.
Ice storms occur when a rain bearing warm front arrives in a area of cold
dense air, and the rain freezes as soon as it lands.
Storm surge is the combined effect of strong winds and low barometric
pressure causing waves to 'pile up' against coasts.…read more


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