2. Collective reports are a collection of the individual reports received by a central station or office and transmitted to other central offices. They are of three classes: Class 1.-The central office in this case is usually the main office of a country; it transmits its reports, within 14 hours of the time the observations are taken at the individual stations, to all main offices of other countries within a radius of 1,500 kilometres. Class 2.-These are reports made for the purpose of giving countries over 1,500 kilometres distant information essential to making their own forecasts. The central office is that of a selected State which possesses a high-power wireless station capable of worldwide ranges (minimum range 3,000 kilometres). The report is made within three hours of the observations, and is a collection of reports selected from the Class 1 reports and abridged (see Appendix IV). It should include a forecast of conditions in the country of origin. Class 3.-These are local reports made by local centres to other local centres (any within 500 kilometres). The report is a collection of reports, selected from the Class 1 reports from stations in the vicinity and abridged (see Appendix IV). It is made within thirty minutes of the time of observation. APPENDIX II.-SPECIAL REPORTS. Special reports give the results of continuous observations at aerodromes having meteorological stations on recognised air routes. They are to be rendered within thirty minutes of a request from a central office on a specified aerodrome on the route. The maximum distance from which these reports will be required is 500 kilometres. The requests may take the form of a demand for hourly reports. The reports are rendered by telephone or wireless, and may be from one country to another in the case of an international air route. The reports when made by telegram will be in the form and code given in Appendix IV. APPENDIX III.-FORECASTS. Short-period forecasts covering three to four hours will give a statement of the anticipated conditions of cloud, weather, surface wind, and visibility, together with direction and speed of wind at heights of 1,000 and 2,000 metres, and an estimate of meteorological fitness for different types of aircraft. Normal forecasts for twenty to thirty hours will give similar information, but in more general terms. Long-period forecasts give a general statement of the prospects for the next two or three days. Route forecasts are made twice daily by central offices from information received from individual stations and will give a statement of conditions anticipated in the different regions or routes of the country for about six hours ahead. APPENDIX IV. GENERAL FORM IN WHICH REPORTS ARE TO BE RENDERED AND CODES FOR THEIR TRANSMISSION. Individual stations will be allotted station call signs, i. e., an index group of letters or figures which will be used in all reports to indicate the station, and will also serve as the wireless call sign. These should be internationally distinct. The general form is given in meteorological symbols or letters. For purposes of transmission an appropriate figure value is given to cach symbol or letter in accordance with the codes given below. METEOROLOGICAL SYMBOLS OR LETTERS AND THEIR SIGNIFICATION. Standard symbols. BBB=Barometer reduced to sea-level and expressed in millibars and tenths, i. e., corrected for temperature, gravity and index error. The initial 9 or 10 is omitted. DD Direction of wind (true direction as distinguished from magnetic) at a height of 10-15 metres above the surface expressed on scale 1-72 (see Code X). F-Force of wind on Beaufort scale (wind above force 9 to be specially noted at end of telegram). ww Present weather (Code I). = TT=Temperature in degrees A (0° A=-273° C, 273° A= 0° C), first figure omitted. A Form of low cloud (Code III). L=Amount of low cloud (in tenths of sky covered, amount B=Form of medium or high cloud (Code III). V-Visibility (Code V). H, Relative humidity (Code VI). 3 Characteristic of barometric tendency (Code IX). F, Fitness of weather conditions for flying machines (Code F2-Fitness of weather conditions for airships (Code VIII RR=Rainfall: (i) in day, (ii) in night; in millimetres and tenths. MM Maximum temperature in the day. mm=Minimum temperature in the night. X=Reserve figure. SPECIAL SYMBOLS FOR UPPER AIR CURRENTS. H=Height (Code IV (b)). DD Direction on scale 1-72, i. e., to nearest 5° (see Code X). VV Speed in kilometres per hour (for speed above 99 K/hr use three figures). SPECIAL SYMBOLS FOR UPPER AIR TEMPERATURE AND HUMIDITY. p=Height or pressure (Code IV (c)). SPECIAL SYMBOL FOR COLLECTIVE REPORTS, CLASS 2. BB-Barometer in whole millibars with the initial 9 or 10 omitted. GENERAL FORMS OF MESSAGES IN METEOROLOGICAL SYMBOLS. REGULAR REPORTS. 1. Individual Station Reports.-Station call sign followed by the following groups:- BBBDD. FwwTT. ALBMh. wwVHS. BbbF,F2. RRMMX (or RRmmX). Additional two groups for reports from stations having facilities for observations of upper air currents; the first of these being: A five-figure group to indicate that upper air current information is contained in the group which follows and which has the general form HDDVV. Additional two groups for reports from stations having facilities for observations of upper air temperature and humidity; the first of these being: A five-figure group to indicate that upper air temperature and humidity information is contained in the group which follows and which has the general form μTTHH. [NOTE. These indicative five-figure groups would be better, from a signalling point of view, as a special Morse signal.] 2. Collective Station Reports, Class 1.-The individual station reports are given in sequence in the same general form as above. Upper air conditions are given at the end for those stations for which available: upper air currents being given only for the following heights: 500, 1,000, 2,000, 5,000 metres (see Code IV (b)). Example of general form of collective report (Class 1) giving information from four stations, A, B, C, D, of which stations B, C have given upper air currents, and stations B, D upper air temperatures and humidity. Call sign for "A"-BBBDD-FwwTT-ALBMh- Call sign for "B"-BBBDD-FwwTT-ALBMh- 1 2. Call sign for "C" BBBDD - FwwTT- ALBMh wwVHS-3bbF, F, Call sign for “Ď " wwVHS-3bbF1F2. BBBDD-FwwTT-ALBMh Group or signal indicating that upper air current information follows. Call sign for "B"-HDDVV. Call sign for "C"-HDDVV. Group indicating that upper air temperature and humidity information follows. 3. Collective Station Reports, Class 2.-The individual station reports are given in sequence in an abridged form, as follows: Call sign for station-BBDDF-wwTTh-ALẞbb. Upper air currents are given at the end of the telegram for heights 2,000 and 5,000 metres for selected stations. Example of general form of collective report (Class 2) giving information from four stations, A, B, C, D, of which stations "B," "C" are selected for upper air current conditions. Call sign for "A"-BBDDF-wwTTh-ALẞbb. Group indicating that upper air current information follows. Forecast of conditions in country of origin. 4. Collective Station Reports, Class 3.-The individual station reports are given in sequence in an abridged form as follows: Call sign of station-DDF,F2-ALBMh-wwWWV. [NOTE 1.-The general form for transmission of "special reports" and of "forecasts has not yet been formulated.] [NOTE 2.-Observations from ships at sea and the transmission of such observations require special arrangements which it has not yet been possible to formulate. Similarly for observations from aircraft and their transmission.] CODES. Code I.-Present weather.-ww. NOTE.-00 to 49 weather without precipitation; 50 to 70 and 77 to 97 with precipitation. In Codes I and II, r=rain, d=drizzle, h=hail, s=snow, rs=sleet, tlr= thunderstorm, e=wet air, f=fog (see Code V). |