36 INSTRUCTIONS TO MARINE IVIETEOROLOGICAL OBSERVERS 



Jit all times; a precise knowledge of the relation of wind force to 

 the appearance of the sea mnst be gained by experience. 



In recording the force of the wind, the scale devised by Admiral 

 Sir Francis Beanfort is employed. According to this scale, which is 

 contained in the code table for F below, the wind varies from 0, a 

 calm, to 12, a hnrricane, rated as the highest force ever attained. 

 When a weather report is to be transmitted by radio, the proper code 

 number for the wind force in the radio message is the same as the 

 Beaufort number on the form, provided that the wind force is not 

 greater than 9. Since the International Kadio Weather Code per- 

 mits the sending of but one figure for the wind force, wnnds of 

 greater strength than force 9 must be reported by radio in a special 

 manner. The procedure in such cases is as follows : // the loind 

 force is 10^ 11^ or 12^ Beaufort, the force should he reported in the 

 radio message as 9, hut at the end of the report a word, ^^gale^\ 

 ''''storm^\ or '''■hurncane''\ 7'espectivply^ should he added in plain lan- 

 guage. However, the figure 9 should not be entered on the obser- 

 vation foi-m for forces of 10, 11, or 12. Tlie higher force should be 

 recorded there exactly as observed. 



Code table for F (tvind force, Beaufort scale) 



Beiufort number 



Zero 



One..- 

 Two.._ 

 Three. . 

 Four... 

 Five—. 



Six 



Seven.. 

 Eight.. 

 Nine... 

 Ten.... 

 Eleven. 

 Twelve 



Calm 



Light airs 



Light bresze 



Gentle breeze _ 



Moderate breeze 



Fresh breeze 



Strong breeze 



High wind (moderate gale) 



Gale (fresh gale)... 



Strong gale 



Whole gale ' 



Storm 1 



Hurricane > 



Code 

 figures 



' When force is in excess of strong gale the observer uses code figure 9 and adds 

 word "gale", "storm", or "hurricane" (as the case may be) to the end of the message. 



Assuming that the ship is in the open sea where there is an ab- 

 sence of a])preciable current, and that the wind direction and force 

 have remained essentially constant for a sufficient length of time so 

 that the sea surface is in equilbrium, so to speak, with the wdnd, the 

 following conditions usually are observed. With force (calm) the 

 surface of the sea is glassy; with force 1 the sea tends to be rippled 

 in patches. With force 2 the entire surface of the sea is rippled and 

 miniature waves several inches in height are formed. One of the 

 principal distinctions between force 1 and force 2 is afforded by the 

 distinctness with wdiich the sea horizon may be seen on clear days. 

 With force 1 the horizon presents an indefinite line, whereas w^th 

 force 2 the horizon is quite shar):)ly delineated. A Avind force of 3 

 produces a definite Avave formation with scattered incipient white- 

 caps making their appearance. Force 4 is characterized by numerous 

 well-developed Avhiteca])s, Avhich give the ocean a spotted appearance. 

 Force 4 produces a distinct sea which is easily distinguished from 



