Suppression and Dissipation of Weak Tornadoes in Metropolitan Areas: A Case Study of Greater London

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  • 1 Geography Section, Oxford Polytechnic, Oxford, England
  • | 2 Tornado and Storm Research Organisation, Cockhill House, Trowbridge, England
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Abstract

Examination of the distribution of property-damaging tornadoes which have occurred in and around Greater London since 1830 reveals that the inner parts of the metropolis have experienced relatively few tornadoes during the past 150 years compared with the outer areas of the metropolis and the surrounding countryside. The authors suggest that urban factors such as the increased surface roughness of the urban fabric and the urban heat island suppress the formation of tornadoes from some storms which would otherwise have produced tornadoes and to cause the dissipation of some tornadoes already formed outside the urban area when they reach the outer suburbs. These effects appear to be restricted to tornadoes of weak intensity because the small-scale influence of urban areas may be negligible for a large-scale synoptic and meteorological situation producing moderate or severe tornadoes, as evident during the 3 April 1974 tornado outbreak in the United States.

Abstract

Examination of the distribution of property-damaging tornadoes which have occurred in and around Greater London since 1830 reveals that the inner parts of the metropolis have experienced relatively few tornadoes during the past 150 years compared with the outer areas of the metropolis and the surrounding countryside. The authors suggest that urban factors such as the increased surface roughness of the urban fabric and the urban heat island suppress the formation of tornadoes from some storms which would otherwise have produced tornadoes and to cause the dissipation of some tornadoes already formed outside the urban area when they reach the outer suburbs. These effects appear to be restricted to tornadoes of weak intensity because the small-scale influence of urban areas may be negligible for a large-scale synoptic and meteorological situation producing moderate or severe tornadoes, as evident during the 3 April 1974 tornado outbreak in the United States.

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