INSTRUCTIONS TO MARINE METEOROLOGICAL OBSERVERS 35 



he only tenvporary • in coding the radio message^ add the number 

 07 to the code number afpropriate to the observed wind directiooi. 

 This will indicate to the person receiving the message that a squall 

 is occurring at the time of observation or has occurred during the 

 preceding hour, and that an}^ apparent peculiarity in the wind direc- 

 tion is to be regarded as having purely local significance. As a 

 matter of fact, the number 67 should be added to the number for the 

 wind direction whenever squalls have occurred during the hour pre- 

 ceding the observation, even if these squalls did not appreciably 

 change the wind direction. More details in this connection are given 

 in the section containing instructions for recording "present 

 weather." 



Code table for DD (loind direction) 



[Direction from which wind is blowing] i 



Rapid and pronounced changes of the wind should be noted under 

 the heading "Daily Journal" on Form 1210A. In recording any 

 large change the observer should specify the time at which it oc- 

 curred, the direction of the change, and the force on the Beaufort 

 scale; for example, "at 10 a. m. wind veered from SE, 3, through 

 S, toW, 8." 



Observers sometimes fail to distinguish between shifting winds 

 and variable winds. The term "shifting" applies to winds whose 

 direction is changing in accordance with the movement or develop- 

 ment of some well-marked cyclonic or anticyclonic system. The 

 term "variable" applies to weak winds (force 3 or less) whose direc- 

 tion is indefinite, coming in feeble puffs, first from one point, then 

 from another. The term "variable" should be applied also to the 

 strong but short-lived winds which are associated with local squalls. 



Wi7id force {F). — To an experienced observer the appearance of 

 the sea surface serves as the best means of estimating the true wind 

 force, just as it affords the best means of ascertaining correctly the 

 wind direction. However, the appearance and the roughness of the 

 sea obviously depend upon a number of factors, and not solely on the 

 strength of the wind locally. The length of time the wind has been 

 blowing and the rate at which it is changing its direction and velo- 

 city are some of the more important influences. Consequently it is 

 virtually impossible to lay down reliable criteria which will be valid 



