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sent in the International Meteorological Code, a copy of which may be obtained by 

 application to the Weather Bureau. 



It is to be noted that it is obligatory for every master of a vessel to report any 

 danger to navigation. This includes the reporting of tropical storms or other seriously 

 bad weather which might endanger shipping. 



1452. Storms at Sea 



When vessels are operating in areas where bad weather predominates, or where 

 typhoons or hurricanes prevail during certain seasons, intense studies of these phe- 

 nomena must be made by the survey personnel. Much valuable data on winds and 

 cyclonic storms will be found in Chapters 21 and 22 of H. O. Publication No. 9, American 

 Practical Navigator (Bowditch). 



1453. Local W^eather Conditions 



Meteorological conditions often seriously impede the progress of the survey. Few 

 operations in a hydrographic survey can be conducted with efficiency and acciu-acy 

 during stormy weather and much of the work requires exceptionally good weather. 

 The Government weather forecasts deal with general conditions, but the conditions 

 that must be considered in planning the day-to-day field operations are frequently 

 local and it is only by long experience and a determined study of these, based on the 

 general forecast and supplemented by personal observation, that full advantage can 

 be taken of them. 



Weather conditions vary from the almost perfect (encountered in certain tropical 

 regions) to the consistently bad (prevalent along certain portions of the coast) . Under 

 the latter, which may consist of stormy weather or fog and haze, the execution of the 

 work is a constant struggle, and the ability to predict the local weather is an asset to 

 any survey party. Since the cloud forms and other meteorological characteristics that 

 forerun certain changes in weather in one locality often precede widely dift'ering weather 

 in another locality, it is obvious that forecasting can be done only by one with con- 

 siderable local experience. 



There is a regularity about certain phases of local weather which, after a knowledge 

 of it has been gained, may be used to advantage in planning the field work. For 

 example, the diurnal change in temperature and pressure along the coasts results, in 

 summer in particular, in a sea breeze which begins in the morning between 9 and 11 

 o'clock after the land warms, and dies away in the late afternoon, being then replaced 

 by a land breeze which blows gently until morning. In the Tropics, this phenomenon 

 is repeated with great regularity. 



In some localities there is a dependable cycle of weather conditions during which 

 a period of calm or exceptionally clear weather may be expected at the same regular 

 position in the cycle. For example, along the southeastern coast of the United States, 

 periods of stormy southeasterly weather are regularly followed by a north to north- 

 westerly wind which blows offshore, accompanied by comparatively clear atmosphere. 

 The trend of the coastline in the locality forms a lee, so that even during moderate 

 winds, the sea is calm inshore and survey operations may be conducted there. 



For certain phases of the field operations, exceptionally clear weather is required. 

 This can only be predicted from a local knowledge of the area. It has been noted, for 

 example, that along the southeastern coast of the United States periods of such weather 



