Besides providing us with the material to make a detailed history of weather and climate over Europe during the 1780s, a series of daily weather maps can also be used to determine whether or not the circulation patterns of the 1780s have any significance or bearing on the kind of atmospheric behaviour which has been prevalent in recent years.

It is convenient to reduce the mass of meteorological information depicted on a sequence of daily charts into a less unwieldy form by classifying the analysed synoptic situations according to schemes of defined weather types and circulation patterns. This opens up the way for the daily weather situations to be investigated according to statistical methods and techniques which have been developed in synoptic climatology during the twentieth century.

The area covered by the charts allows two well-tested methods of classification to be applied: the Lamb system of British Isles weather types (1972); and the scheme of European large-scale weather patterns [Grosswetterlagen]developed by Baur (1947) and later revised and extended by Hess and Brezowsky (1977). By using both classifications the circulation patterns depicted on the charts can be examined from two points of view, i.e. according to the weather conditions over both the British Isles and Central Europe. A more comprehensive picture about the characteristic features of the circulation can thus be obtained.

Lamb British Isles weather types

Dealing first with the British Isles weather types, this classification comprises seven main types, which are defined as follows:

W Westerly: high pressure to the south, sometimes also to the south-west and south-east, and low pressure to the north of the British Isles. Sequences of depressions and ridges traveling eastwards across the North Atlantic and further eastward.