16. We sought evidence from the Meteorological
Office on the severity of the storm. This revealed that recorded
mean wind speeds at stations across Northern Ireland ranged from
Gale Force 8 to Violent Storm Force 11.
Higher wind speeds will undoubtedly have occurred in some locations.
At Aldergrove, new records were set for both gust speeds and storm
duration. Severe Gale Force 9 criteria were met for five consecutive
hours and Gale Force 8 criteria for 10 consecutive hours.
This was the most severe "wind event" there, on both
grounds, since records began in 1928.
17. The storm also affected considerable areas
of the Republic of Ireland, southern Scotland and northern and
north western England in particular. Hurricane force mean wind
speeds were recorded at Malin Head, County Donegal, and gusts
of 109 mph were recorded there and 107 mph at Belmullet, County
the public electricity supplier in the Republic of Ireland, described
the storm as "the worst to hit the north of the country for
over 35 years."
Scottish Power reported
gusts in excess of 105 mph. Yorkshire Electricity, less severely
affected than areas to the north, commented
that maximum windspeeds over the period 26 to 28 December were
materially higher than had been forecast.
vitably, comparisons have been drawn with the severity of the Christmas Eve 1997 storm. The Meteorological Office reported that this storm was both less severe and of shorter duration, lasting some two to three hours, than the 1998 storm.
19. We also asked the Meteorological Office
for its assessment of t
he statistical frequency with which such storms as the Boxing Day storm could be expected in Northern Ireland.
On the assumption that such storms are independent events, its
judgement was that, in any year, the statistical probability of
such a storm recurring at Aldergrove in that year is less than
one in a hundred. The Meteorological Office did stress, though,
that this is a statistical average; there is no guarantee that
such an event would not repeat next year. Equally, it might be
200 years, or more, before there is a recurrence. By contrast,
the return period of a storm, at Aldergrove, of the intensity
d duration of the 1997 storm there is estimated to lie in the five to eight year range.
20. In view of concerns about the possible impact
of global warming on the climate, we subsequently sought the views
of the Meteorological Office on the possibility that such storms
might become more frequent as a result of global warming. It would
appear that there are natural variations in storminess around
the British Isles, occurring over periods of decades to centuries,
and that it is indeed possible that the greenhouse effect may
influence storminess in the future, causing an increase in the
and severity of storms.
However, little is known as to how the two factors might interact,
so the extent to which historical extrapolation is relevant to
predicting future trends is uncertain.
15 Appendix 23, p. 104. Back
16 Appendix 23, p. 104. Back
17 Appendix 23, p. 104. Back
18 Electricity Supply Board Back
19 Appendix 19, p. 83. Back
20 Appendix 16, p.82. Back
21 Appendix 11, p. 75. Back
22 Appendix 30, p. 113. Back
23 For information on the severity of the weather conditions in Great Britain, see OFFER report, paras. 2.1 to 2.6. Back
24 Appendix 30, p. 113. It should be noted, though, that the two storms principally affected different parts of Northern Ireland: the 1997 storm had greatest effect in the south east parts of Northern Ireland. Back
25 Appendix 30, p. 114. Back