This paper is concerned with an aspect of extensive city fires which is nowadays usually associated with war time conditions, namely the fire storm. The best known examples, perhaps, are those which occurred in fires initiated by heavy bombing raids on German cities during World War II, especially Hamburg in July 1943, which resulted in heavy loss of life, although there are reports of fire storms in many great historic fires including, for example, the Great Fire of Konigsberg in 1764. The term "fire storm" is often used subjectively by people who have experienced the conditions occurring in one, and it appears from their description that the distinguishing characteristic of the fire storm is a high wind, in many cases reported to be of hurricane force. Observers also report high intensities of radiation, but these are characteristic of all large fires. War time fire storms followed bombing attacks in which a high proportion of the buildings in a large area were set on fire within a short space of time; these conditions may well follow the explosion of nuclear weapons, and this has led to considerable civil defense interest in the fire storm. It is now more than 20 years since the violent fire storms of World War II, but the passing years have tended, in many ways, to obscure rather than clarify our concept of the fire storm. This paper is an attempt to assign a definite meaning to the term, to show that a fire storm is a consequence of the interaction of a large number of fires, irrespective of meteorological conditions, to evaluate as far as possible the wind conditions in a fire storm area, and to provide some rational basis for the prediction of the minimum area of fire in which fire storm conditions can occur in a given type of built-up area.

[This publication is referenced in the "Synthesis of knowledge of extreme fire behavior: volume I for fire managers" (Werth et al 2011).]