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 on 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.
How the Storm Compared
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
- 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)
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.
Once Every 200 Years
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
Temperature & Pressure
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.
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
Journalists, looking for a sensational story, accused the Met Office of failing to forecast the storm correctly. 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 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.
