PART I. THE OCEAN WEATHER SERVICE 



Tlie ocean meteorological program of the Weather Bureau has two 

 separate and distinct parts. First, there is the daily service by radio. 

 Owing to the need for brevity, the radio reports contain a limited 

 amount of essential information. The daily weather reports from 

 ships and islands reveal the conditions over the ocean ; when assem- 

 bled on a map, including continental reports, they give a picture of 

 weather conditions existing momentarily over a large region. A 

 collection of observations is immediately returned to the mariner by 

 radio broadcast so that he may draw his own weather map on ship- 

 board. By this process, the weather at the earth's surface is mapped 

 and much'can be inferred as to conditions above the surface. Forma- 

 tion and movement of storms are revealed; advices and warnings 

 of storms and forecasts of wind and weather are included in the 

 broadcasts for the benefit of the mariner. For this first part of 

 the Weather Bureau's program, observations are secured by radio 

 from certain areas of the Pacific and Atlantic (including the Gulf of 

 Mexico and the Caribbean Sea). This service is of great value to 

 agriculture and commerce as well as navigation; the daily weather 

 forecasts for land areas depend to a considerable extent upon the 

 ocean weather observations. To a very large degree ships' weather 

 reports form the basis of warnings of the destructive storms that 

 sometimes move from the ocean into coastal areas. 



As the second part of the program, the Weather Bureau uses more 

 complete reports, forwarded by mail at the end of the voyage, in 

 order that the weather of the oceans may be studied in greater 

 detail. Results of these studies are the wind roses and weather data 

 in other forms, as they appear on the pilot charts, also weather sum- 

 maries for all parts of the oceans published for the information of 

 the navigator. The life histories of important storms at sea are 

 determined and recorded from ships' weather observations. Infor- 

 mation regarding weather conditions at sea is furnished for use in 

 admiralty cases. Observations are used in connection with land 

 data for the construction of weather maps of world areas. Since the 

 oceans influence the weather of the continents, the study of ocean 

 temperatures is one of the important lines of work of the Bureau. 



For these purposes the detailed entries of the mail report are of 

 great value. It is a world-wide problem, hence mail reports are 

 desired from every part of the oceans. While radio reports of the 

 weather are required twice or even four times daily, the observations 

 that are sent only by mail are required once each day at Greenwich 

 mean noon, with appropriate notes in the Dailj^ Journal as to condi- 

 tions between observations. 



Since the last edition of this manual was published (1929), the 

 meteorological services of maritime nations have made much prog- 

 ress in standardizing their methods of reporting ocean weather, par- 

 ticularly by radio. The International Figure Code is used in radio 

 weather messages that are easily understood by seamen of all nation- 



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