[ . . . ] The impression created by viewing a burnt-out city pales beside the fire itself: the howling of the firestorm, the cries and moans of the dying and the crashes of the falling bombs. [ . . . ]
The reason for the damage being so serious and, above all, for the unusual number of deaths compared with previous raids, is the fact that firestorms developed. They, and in particular the one during the second major attack on the night of 27/8 July, created a situation which must be described as novel and hitherto inconceivable in every respect.
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Firestorms and their characteristics are established phenomena well known in the history of urban fires. The physical explanation for them is simple. As a result of a combination of a number of fires the air overhead becomes heated to such an extent that, because of its reduced specific gravity, it develops a tremendous upward pressure which creates a very strong suction effect on the surrounding air masses pulling them towards the center of the fire in a radial direction. As a result of the firestorm and, in particular, the tremendous suction effect, winds are produced which are even stronger than the well-known wind strengths [1-12]. As in the case of meteorology so also in the case of firestorms the air movement is produced by a rebalancing of differences of temperature. But, while in the case of meteorology these temperatures are generally of the order of 20–30 degrees Celsius, in the case of firestorms there are temperature differences of 600 or even 1,000 degrees. This explains the huge force generated by the firestorms which cannot be compared with normal meteorological processes. [ . . . ]
The development of a firestorm is encouraged or hampered by the architectural conditions of an affected area in the same way as by the type, extent and size of the original fires. In Hamburg the firestorms originated in areas in which the buildings were close together and densely populated and in which, therefore, the type and density of the buildings affected already provided favorable preconditions for the development of a firestorm. The affected areas in Hamburg were characterized by narrow streets with big blocks of flats with large numbers of courtyards, terraces etc. In these yards fireballs could develop very rapidly which became, in the truest sense of the word, mantraps. The narrow streets formed fire channels through which the long flames were whipped.