Attachments
INTRODUCTION
Apart from a short break 1940 - 1946, surface observations of meteorological elements since 1884 have been summarized and published in ‘Meteorological Results, Part I—Surface Observations’. Part II contains summaries of upper-air observations and the series began in 1947. This series, ‘Meteorological Results, Part III—Tropical Cyclone Summaries’, is concerned with tropical cyclones which formed over the western Pacific and the South China Sea.
During the period 1884 - 1939, reports on destructive typhoons were occasionally prepared and were included in the Appendices of Meteorological Results, Part I. However, since 1947, this practice was ex- tended and information on all tropical cyclones which caused gales in Hong Kong was contained in the Annual Departmental Reports of the Director of the Royal Observatory.
Tracks of tropical cyclones in the western Pacific and the South China Sea were published in Meteorological Results, Part I up to 1967. For the period 1884-1960, the tracks were plotted with day circle positions only. The day circle time varied to some extent but has remained fixed at 0000 h G.M.T. since 1944. The day circle time used in each tropical cyclone is given in the Appendix of Royal Observatory Technical Memoir No. 7. From 1961 onwards, 6-hourly intermediate positions were also shown on the tracks of all tropical cyclones.
Provisional reports on individual tropical cyclones affecting Hong Kong have been prepared since 1960; this was done in order to meet the immediate needs of the press, shipping companies and others. These reports were in cyclostyled form and were supplied on request. Initially, reports were only written on those tropical cyclones causing gale signals to be hoisted in Hong Kong, but by 1968 it had become necessary to produce individual reports for every tropical cyclone for which any local Storm Warning Signal was raised. .
In, this publication, tropical cyclones are classified into the following four categories according to ‘the maximum sustained winds within their circulations : —
A TROPICAL DEPRESSION (T.D.) has maximum sustained winds of less than 34 knots and at this stage the centre is often not very clearly defined and cannot always be fixed precisely. /
A TROPICAL STORM (T.S.) has maximum sustained winds in the range 34 - 47 knots.
A SEVERE TROPICAL STORM (S.T.S.) has maximum sustained winds in the range 48 - 63 knots.
A TYPHOON (T.) has maximum sustained winds of 64 knots or more.
Local wind observations are regularly made at 6 stations located at suitable points in the Colony. Each station is equipped with a Dines pressure-tube anemograph incorporating a twin-pen direction recorder, manufactured by R. W. Munro Limited. Quick-run mechanisms are also fitted to the anemometers at Hong Kong Airport, Waglan Island and Tate’s Cairn for recording the fine structure of the wind flow in typhoons for research purposes. Details of these stations are given below. The position shown is for the barometer where applicable and the elevation of the ground is for the ground near the thermometer shelter, except at Tate’s Cairn which was built for the operation of the Plessey Type 43S 10 cm radar. In all cases the height of the head of the anemometer refers to Mean Sea Level.