The
Great Storm of 1987 |
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In southern England, 15 million
trees were lost, among them many valuable specimens.
Trees blocked roads and railways, and brought down electricity
and telephone lines. Hundreds of thousands of homes in
England remained without power for over 24 hours.
Falling trees and masonry damaged or destroyed buildings
and cars. Numerous small boats were wrecked or blown
away. A ship capsized at Dover, and a Channel ferry
was driven ashore near Folkestone.
The storm killed 18 people in England and at least
four more in France. The death toll might have been
far greater had the storm struck in the daytime.
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Fig 1: Storm Damaged Trees
(photo © K Herrington)
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Four or five days before the storm struck, forecasters predicted
severe weather on the following Thursday or Friday. By mid-week,
however, guidance from weather prediction models was somewhat equivocal.
Instead of stormy weather over a considerable part of the UK, the
models suggested that severe weather would reach no farther north
than the English Channel and coastal parts of southern England.
During the afternoon of 15 October, winds were very light over
most parts of the UK. The pressure gradient was slack. A depression
was drifting slowly northwards over the North Sea off eastern Scotland.
A col lay over England, Wales and Ireland. Over the Bay of Biscay,
a depression was developing.
The first gale warnings for sea areas in the English Channel were
issued at 0630 UTC on 15 October and were followed, four hours
later, by warnings of severe gales.
At 1200 UTC on 15 October, the depression that originated in the
Bay of Biscay was centred near 46° N, 9° W and its depth was 970
mb. By 1800 UTC, it had moved north-east to about 47° N, 6° W,
and deepened to 964 mb.
At 2235 UTC, winds of Force 10 were forecast. By midnight, the
depression was over the western English Channel, and its central
pressure was 953 mb. At 0135 on 16 October, warnings of Force 11
were issued. The depression now moved rapidly north-east, filling
a little as it did, reaching the Humber estuary at about 0530 UTC,
by which time its central pressure was 959 mb. Dramatic increases
in temperature were associated with the passage of the storm's
warm front.
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Fig
2: Maximum gusts (knots)
during the 1987 storm |
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It's clear that for sea areas, warnings of severe weather were
both timely and adequate. Forecasts for land areas, however, left
much to be desired.
During the evening of 15 October, radio and TV forecasts mentioned
strong winds but indicated that heavy rain would be the main feature,
rather than strong wind. By the time most people went to bed, exceptionally
strong winds hadn't been mentioned in national radio and TV weather
broadcasts.
Warnings of severe weather had been issued, however, to various
agencies and emergency authorities, including the London Fire Brigade.
Perhaps the most important warning was issued by the Met Office
to the Ministry of Defence at 0135 UTC, 16 October. It warned that
the anticipated consequences of the storm were such that civil
authorities might need to call on assistance from the military.
In south-east England, where the greatest damage occurred, gusts
of 70 knots or more were recorded continually for three or four
consecutive hours.
During this time, the wind veered from southerly to south-westerly.
To the north-west of this region, there were two maxima in gust
speeds, separated by a period of lower wind speeds. During the
first period, the wind direction was southerly. During the latter,
it was south-westerly. Damage patterns in south-east England suggested
that whirlwinds accompanied the storm. Local variations in the
nature and extent of destruction were considerable.
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How the storm measured up |
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Comparisons of the October 1987 storm with previous severe storms
were inevitable. Even the oldest residents of the worst affected
areas couldn't recall winds so strong, or destruction on so great
a scale.
- The highest wind speed reported was an estimated 119 knots
(61 m/s) in a gust soon after midnight at Quimper coastguard
station on the coast of Brittany (48° 02' N 4° 44' W)
- The highest measured wind speed was a gust of 117 knots (60
m/s) at 0030 UTC at Pointe du Roc (48° 51' N 1° 37' W) near Granville,
Normandy
- The strongest gust over the UK was 106 knots at 0424 UTC at
Gorleston, Norfolk
- A gust of almost 100 knots occurred at Shoreham on the Sussex
coast at 0310 UTC, and gusts of more than 90 knots were recorded
at several other coastal locations
- Even well inland, gusts exceeded 80 knots: 82 knots was recorded
at London Weather Centre at 0250 UTC, and 86 knots at Gatwick
Airport at 0430 UTC (the authorities closed the airport)
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Fig 3a: Once-in-50-year
gust speed (metres/sec) over open level country. Data up
to 1971. |
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Fig 3b: Once-in-50-year
hourly mean wind speed (metres/sec) over open level country.
Data up to 1971. |
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TV weather presenter Michael Fish will long be remembered for
telling viewers, the evening before the storm struck, that there
would be no hurricane. But he was unfortunate. Fish was referring
to a tropical cyclone over the western part of the North Atlantic
Ocean that day. This storm, he said, would not reach the British
Isles - and it didn't.
It's worthwhile to consider whether or not the storm was, in any
sense, a hurricane - the description applied to it by so many people.
In the Beaufort scale of wind force, Hurricane Force (Force 12)
is defined as a wind of 64 knots or more, sustained over a period
of at least 10 minutes. Gusts, which are comparatively short-lived
(but cause much of the destruction) are not taken into account.
By this definition, Hurricane Force winds occurred locally but
were not widespread.
A 10-minute mean wind speed of 70 knots (an average over 10 minutes)
was recorded at Lee on Solent in Hampshire, and an hourly-mean
speed of 68 knots at Gorleston. The highest hourly-mean speed recorded
in the UK was 75 knots, at the Royal Sovereign Lighthouse. Winds
reached Force 11 (56-63 knots) in many coastal regions of south-east
England. Inland, however, their strength was considerably less.
At the London Weather Centre, for example, the mean wind speed
did not exceed 44 knots (Force 9). At Gatwick Airport, it never
exceeded 34 knots (Force 8).
The Great Storm of 1987 did not originate in the Tropics and was
not, by any definition, a hurricane - but it was certainly exceptional.
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South-east of a line extending from Southampton through north
London to Great Yarmouth, gust speeds and mean wind speeds were
as great as those which can be expected to recur, on average, no
more frequently than once in 200 years. So, comparison with the
great storm of 1703 was justified. The storm of 1987 was remarkable
for its ferocity, and affected much the same area of the UK as
its 1703 counterpart.
Northern Scotland is considerably closer to the main storm tracks
of the Atlantic than south-east England, so storms as severe as
October 1987 can be expected far more frequently than once in 200
years. Over the Hebrides, Orkney and Shetland, winds as strong
as those which blew across south-east England in October 1987 can
be expected once every 30 to 40 years.
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Fig
4: Example of station
temperature graph changes |
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The 1987 storm was also remarkable for the temperature changes
that accompanied it. In a five-hour period, increases of more than
6 °C per hour were recorded at many places south of a line from
Dorset to Norfolk.
Especially rapid and large was the increase at South Farnborough
in Hampshire, where the temperature rose from 8.5 °C to 17.6 °C
in 20 minutes. The return frequency for a temperature increase
this rapid is, like the return frequency for the wind strengths
that occurred in the storm, about once in 200 years. Across southern
England, rapid increases in temperature were followed by sharp
decreases.
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Fig
5: Example of station
temperature changes |
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Ahead of the storm, barometric pressure had fallen rapidly, but
neither the magnitude of the fall nor the rate of decrease was
remarkable. The subsequent rise in pressure was, however, exceptional.
Over much of southern England, increases of more than 8 mb per
hour were recorded, with the most rapid at Hurn in Hampshire, where
pressure rose 12.2 mb in one hour.
The greatest rise over three hours occurred at the Portland Royal
Naval Air Station in Dorset, where, between 0300 and 0600 UTC,
the rise was 25.5 mb. This was, by some margin, the greatest change
in pressure - either upwards or downwards - ever recorded in three
hours anywhere in the British Isles. At many places in southern
England, the pressure rose more than 20 mb in three hours. The
return period for such an occurrence is, again, roughly once in
200 years.
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Fig
6: Surface pressure, wind
flow and fronts, 0000 to 0600 |
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Journalists, looking for a sensational story, accused the Met
Office of failing to forecast the storm correctly. Repeatedly,
they returned to the statement by Michael Fish that there would
be no hurricane - which there hadn't been. And it mattered not
that Met Office forecasters had, for several days, been warning
of severe weather. The Met Office had performed no worse than any
of its European counterparts when faced with this exceptional weather
event.
However, good was to come of this situation. Based on the findings
of an internal Met Office enquiry, scrutinised by two independent
assessors, various improvements were made. For example, observational
coverage of the atmosphere over the ocean to the south and west
of the UK was improved by increasing the quality and quantity of
observations from ships, aircraft, buoys and satellites, while
refinements were made to the computer models used in forecasting.
In an ideal world, storms like 1703 and 1987 will never take us
by surprise. In the real world, however, we must remember that
caprices of the atmosphere may occur at any time.
We must remember, too, that the mathematical models used in numerical
weather forecasting, though remarkably successful, can never fully
represent the complexity of the real atmosphere. And complete observational
coverage of the atmosphere over the oceans west and south of the
British Isles will probably never be achieved.
Extreme weather events, as the storm of 1987 showed, will always
be very difficult to forecast.
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Knowledge and understanding of places
- Location of places and environments studied; places and environments
in the news
Breadth of study
- Causes and effects of a hazard and human responses to it
- Basics of weather and climate
- Management of environments (if something is included about
the ways authorities approached the task of clearing fallen and
damaged trees in woodlands and parks, and about the lessons learned
about dealing with fallen/damaged trees)
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