Transcript L5 UK Stormsx

UK Storms
Aims:
To complete a detailed case
study on The Great Storm in the
UK in 1987.
Storms that Hit the UK are Temperate Storms
1) Temperate storms occur in temperate climates – these are climates that are found
at mid-latitudes, 30-60° north or south of the Equator.
2) They range form mild (e.g. rain showers and 15-30 km/h winds) to severe (e.g.
thunderstorms and 120 km/h winds). They can bring strong winds, rain, hail, sleet or
snow.
3) They generally cause less damage than tropical storms. Typical impacts include road
closures, power cuts and damage to trees. Occasionally temperate storms can be very
severe, with winds strong enough to damage buildings.
4) Temperate storms are caused by depressions:
• Depressions often form over the sea in autumn when the water is warm –
warm surface water leads to warm, moist air which rises. When this
warm air meets the polar front it rises rapidly above the cold polar air
creating an area of low pressure, along with condensation and heavy rain.
• A steep pressure gradient between the two air masses drives strong
winds, which spiral around the depression.
• Steep temperature gradients in a depression affect the storm’s
strength – a strong temperature gradient means there is also a stronger
pressure gradient (warm air has lower atmospheric pressure than cold
air) which drives strong winds.
The Great Storm Hit the UK in 1987
On the night of the 15th October 1987 the UK and France were hit by a severe
temperate storm…
4) On the 15th October, pressure in the centre
The Storm was Caused by a Depression
of the depression fell from 970 mb at
with Rapidly Falling Air Pressure
midday to 953 mb at midnight (much lower
than the average air pressure in the UK –
1) The depression began over the Bay of Biscay
1013 mb).
(north of Spain and west of France) as south
5) The storm hit the south coast of Cornwall
westerly winds carrying warm, wet air from the
and Devon shortly after midnight, moved
North Atlantic met north easterly winds
across the Midlands, and reached the
carrying cold air from the Pole.
Humber Estuary on the east coast at around
2) The depression deepened rapidly due to
5.30 am on the 16th October.
unusually warm sea surface temperatures in the
6) The South East suffered especially severe
Bay of Biscay and a steep temperature gradient
winds between 3 and 6 am, with gusts up to
between the two air masses. Low atmospheric
196 km/h at Gorleston in Norfolk. The
pressure in the core of the depression led to the
highest hourly mean wind speed was
development of very strong winds.
recorded at Shoreham-by-Sea, where winds
3) The polar front jet stream was located further
of 136 km/h blew for 20 minutes
south than normal, so the depression formed
continuously.
over northern France and southern England,
7) After 6 am the depression began to weaken
rather than to the north of Scotland.
and moved over the North Sea.
Impacts included Deaths, Infrastructure Damage and Economic Costs
SOCIAL IMPACTS
• 18 people died in England, and another 4 in France.
• Power and telephone lines were knocked down (mostly by falling trees). 150000
homes lost their telephone connection, and several hundred thousand people had
no electricity for more than 24 hours.
• Some historical buildings were damaged or destroyed, e.g. Shanklin pier on the
Isle of Wight was destroyed by waves.
ECONOMIC IMPACTS
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Over 1 million buildings were damaged. Insurance claims totalled £1.4 billion.
Transport was disrupted as fallen trees blocked roads and railways.
Gatwick airport closed because it had lost power.
Thousands of boats were wrecked. MV Hengist, a cross channel ferry, was
beached.
ENVIRONMENTAL IMPACTS
• About 15 million trees were blown down.
• Some areas lost 97% of their trees, causing a loss of woodland habitat.
Responses included Clean Up Operations and Improved Forecasting
1) During the storm emergency authorities (e.g. fire, police, ambulance, and coastguard) dealt with huge
numbers of emergency calls – four months’ worth of calls in one night.
2) After the storm a massive recovery and clean up operation began:
• Phone companies and electricity boards worked round the clock repairing and replacing equipment until
phone lines and power were restored.
• Highways agencies began clearing roads, and railway companies cleared railways.
• Forestry workers began collecting the fallen trees in forests (around 4 million m3 of timber needed
recovering). It took hundreds of workers over two years to collect and store all the timber.
• The Forestry Commission established the Forest Windblow Action Committee to help woodland owners
recover fallen trees and offer advice on replanting.
3. The Met Office were criticised for how they forecast the storm and issued warnings:
• Severe storm warnings were only issued about three hours before the storm hit.
• The Ministry of Defence were only warned that military assistance might be needed to help deal with
the impacts of the storm at around 1 am on 16th October.
4. There was an inquiry, and changes were made:
• More observations of weather systems are now made by ships, aircraft and satellites.
• Improved computer models are now used to forecast weather.
• The government established a national severe weather warning service to improve the way severe
weather warnings are made and issued.
Exam Question
Describe the impacts of, and responses to, one
temperate storm that you have studied.
(10 marks)