21 

 CHAPTER III. WIND 



3000. GENERAL 



3001. Marine observers may determine the direction and speed of the 

 wind from the direction and character of the ripples, waves and spray. Wind 

 determined in this manner is termed the true wind, and will be entered in 

 Form 615-5. 



3002. The wind experienced on a moving ship is termed the apparent 

 wind, and is the result of two motions- -that of the ship and that of the air. 



3003. Wind is classified as "gusty" when it is characterized by sudden, 

 intermittent increases in speed, with at least 9 knots variation between 

 peaks and lulls. 



3100. WIND DIRECTION 



3110. GENERAL. Wind direction is the true (not magnetic) direction 

 from which the wind is blowing. Whenever possible, the true wind direction 

 will be determined by observing the direction from which ripples, small 

 waves and sea spray are coming, since they run with the wind. When the 

 true wind direction cannot be determined in this manner, use the procedure 

 described in paragraph 3310. 



3120. ENTRY OF WIND DIRECTION DATA (dd) ON FORM 615-5. Select 

 the code figures from Code Table 4 corresponding to the true wind direction 

 (dd), and enter the two figures in column 8. 



CODE TABLE 4 



Symbol dd. — True ilim-lioii. iti lO's of degrees. FROM whuh wiinl i< 



NoTK. — In Qa.se the true wind .speed exceeds 99 knots. .50 will be added 

 to "dd" and only the wind .^peed in excess of 100 Ivuots will be coded. 

 For example, if direction = 163° and speed=121 knots, the wind will 

 be coded as •■6621" (d(l= 16^-50; ff=121-100) 



