Von: joel carlinsky
Datum: 02/17/05 03:13:24
The Great Storm in South East England - October 1987
The pressure situation:
Midnight - 16th October 1987
An intense depression (960mb) situated over the north west coast of Cornwall is expected to move rapidly north east.....
Satellite sequence from Meteosat
14th to 17th October 1987
The great storm of October 1987 was the worst to affect the south east of England since 1703. After the storm had passed the landscape was changed - some 15 million trees were felled and whole forests decimated. Buildings suffered severe damage and ships were driven on to shore. 16 people died as a direct result of the storm damage. The storm developed rapidly - so much so that weather forecasters were unable to predict the track and ferocity of the storm. As it became apparent
that this was an abnormal condition, severe warnings were flashed to emergency services.
Date Time Event
11th October - High winds and heavy rain forecast for the end of the week
15th October 12:00 Depression expected to track along the English Channel, producing fresh to strong winds (Beaufort Force 5 to F7)
15th October 21:30 Warning of strong winds gusting to 50Km/hr given on TV weather forecast (Force 9 - 10)
16th October 00:30 Radio shipping weather forecast warnings of severe gale conditions for sea areas Thames, Dover, Wight, Portland
16th October 01:30 Police and fire services alert issued: Extreme wind conditions expected
16th October 05:30 Wind velocity of 94Km/hr recorded at Heathrow airport, in excess of 100Km/hr on the south coast: roads and railway lines blocked by fallen trees, substantial damage created
16th October 08:00 Centre of intense depression reaches the North Sea, tracking across Buckinghamshire, Cambridgeshire to the Wash. Strongest winds in the south easterly quadrant.
This severe storm originated as a small disturbance along a cold front in the Bay of Biscay (see satellite images). In this location there was only limited weather information available from passing ships and aircraft, current (1997) automatic weather buoys were not in position to transmit remote data. The satellite images show a fairly typical depression developing as warm air from Africa moves north to confront cold air from the Arctic air mass. Where the two air masses met, a frontal system developed,
with the warm air being forced to rise above the cold, creating a drop in air pressure. At about 18:00 on 15th October, the depression suddenly deepened giving a central pressure reading of 958 mb and with a very steep pressure gradient.
Why this occured is still uncertain, but could be the result of interaction between a strong jet stream (air from Hurricane Floyd moving up the east coast of the USA and across the Atlantic) and exceptional warming over the Bay of Biscay. As a result, large quantities of water vapour condensed to cloud providing an enormous release of latent heat energy, driving the winds
of the storm and deepening the central pressure. At this stage the storm was predicted to track along the English Channel.
However, the suddenly deeper depression veered north to track along the north coast of Cornwall and Devon, across central southern midlands to the Wash, catching the weather forecasters by surprise. The strongest winds were recorded in the south easterly quadrant of the storm, crossing the English side of the Channel and through Hampshire, Sussex, Surrey and Kent.
Fortunately, the stongest winds occured in the early hours of the morning when few people where about. Had it occured during a normal working day it is likely that the death toll of 16 would have been substantially higher. As it was, an estimated 15 million trees were uprooted including one third of the famous Kew Gardens in London. Roads and railways were blocked and most people found it impossible to travel to work the following day. A Sealink cross channel ferry was blown ashore at Folkestone.
Clearing up took much time and effort. Electricity supplies were gradually restored using crews brought in from the north of England that had escaped the severe damage. Some rural areas were still without mains power several
days later. Insurance claims reached an all time record amount - and prompted an increase in premiums in 1988!
Weather forecasters were heavily criticised after the event, TV weatherman Michael Fish came in for a large amount of criticism after he answered a viewers query, 'a lady has rung in to ask if there is going to be a hurricane tonight ...... there is not!" This comment came to represent the public's view of the failure to predict the storm. The reality is, of course, more complex. This was an exceptional event and there was a lack of real-time data that would have enabled the sudden drop in pressure and the changing track to have been observed. Michael Fish was quite correct - this was not a hurricane and one was not expected. It was a quite exceptional storm for the UK and many regarded it as a hurricane. But a true hurricane
has winds that are far stronger (120 to 160 mph) and brings far greater quantities of rain than fell during the passage of this storm. As a result of the criticism the Met. Office have improved their severe weather warnings and these are now much more readily and frequently distributed.
This was the 'one in 300 years' event that shook everyone - with far higher winds and destruction than had been recorded since 1709. But another severe storm swept across England on 25th January 1990 - just 27 months later!