Great Storm of 1987 - Development

Development

Four or five days before the storm struck, forecasters had predicted bad weather on the following Thursday or Friday, 15–16 October. By midweek, 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 which 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 0140 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.

It is now clear that for sea areas, warnings of severe weather were both timely and adequate, although forecasts for land areas 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 wind. By the time most people went to bed, exceptionally strong winds had not 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 (130 km/h; 81 mph) 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.