Nicholas Betts

Storm-force Winds of February 1994 Black Out Ulster

Within the lasi three to four decades, it has become progressively clear that, largely as a result of the pace of technological innovation, humanity is no longer restricted lo the entirely passive role with respect (o the atmosphere that characterised the life of past humankind. At the same time, it has become equally clear that the relationships between climate and society have inevitably developed in a highly complex way. Nevertheless, humanity is still subject to the age-old. natural variations of the atmosphere. Advances in weather forecasting have accomplished a great deal in the prediction of severe storms, but. despite the investment of much capital and research effort, the impact of atmospheric hazards shows that the sophisticated economic and social fabric of the modern world is very dependent on climatic and meteorological conditions. Such a viewpoint is exemplified by a recent meteorological event, whereby on 3 February 1994 an active depression tracked northward across western Ireland causing widespread damage, including the worst power failure experienced in Northern Ireland since World War Two. Meanwhile, in the Atlantic Ocean some 400km south-west of Cork, the 26,000 tonnes Maltese registered Christinaki sank with the loss of 27 lives in seas with wave heights in excess of 15m. The synoptic event and its impact upon the island of Ireland, with special reference to Northern Ireland is outlined in this paper. Consideration is also given to the frequency in winter of severe storm episodes, and the apparent inadequate dissemination of information and advice to the general public on such occasions.

The North Antrim Flood of October 1990

The frontal depression of the 27–28 October 1990 was responsible for remarkable rainfall intensities and record floods in northeast Ireland. The synoptic event is described, and the dynamic and orographic influences responsible for the highly localized nature of the mesoscale precipitation signatures outlined. Intense precipitation had its most dramatic impact in Ballycastle and Cushendall. where flooding was widespread. Extreme precipitation was the causal factor, but the event draws attention to perceived changes of flow regimes and landuse in the upper catchments of rivers in North Antrim. A need exists to closely monitor the hydrological characteristics of these catchments in order to calibrate more precisely the flood hazard in this part of northeast Ireland.

AN INDEX OF SUMMERS IN NORTHERN IRELAND

A summer index is presented for Northern Ireland, 1881–1983 to complement those previously published for England and Wales, Scotland, and Ireland as a whole. These sets of indices are compared in discussing the regional variation of summer character within the British Isles. Attempts to identify periodicities of summers of particular character are critically assessed. Markov Chain analysis is applied to the quint sequence of summers in each of the four series, to determine any interdependence between summers. On a year to year basis, results reveal a number of quint summer sequences occurring to be greater, or less, than the random expectations, but overall, no significant single-step first-order Markov memory potential exists. Nor by extending the time interval between events do the four sets of indices reveal statistically significant first-order Markov potential. Markovian analysis shows the complexity of the sequential occurrence of summer character and emphasises the dubious viability of using summer indices for predictive purposes, as has often occurred.