Table 6. Past weather 

 Symbol W — Past weather 



Code 

 figures 



Description 



Cloud covering }{ or less of the sky through- 

 out period. 



Cloud covering more than \i of sky during 

 part of period, and less than >/ 2 during part 

 of period. 



Cloud covering more than % of sky through 

 out period. 



Sandstorm or duststorm or blowing snow. 



Fog or ice fog or thick haze. 



Drizzle. 



Rain. 



Snow or rain and snow mixed or ice pellets. 



Shower(s). 



Thunderstorm (s) with or without precipitation 



Notes 



1. In 0000, 0600, 1200 and 1800 G. C. T. reports "Past Weather" covers the 

 preceding 6-hour period while in 0300, 0900, 1500, and 2100 G. C. T. reports, "W" 

 covers the preceding 3-hour period. 



2. The code figure for "W" is selected in order that "W" and "ww" together 

 give as complete a description as possible of the weather in the time interval 

 concerned. For example, if the type of weather undergoes a complete change 

 during the time interval concerned, the code figure selected for "W" will describe 

 the weather prevailing before the type of weather indicated by "ww" began. If 

 however more than one code figure may be given to W with regard to past weather, 

 the higher code figure is reported. 



Table 7. Cloud amount: total cloud, low cloud 



Symbol N — Fraction of the celestial dome covered by clouds 



Symbol N^ — Fraction of celestial dome covered by type of cloud reported 



jor C L (or Cm if no C L cloud present) 



Symbol N, — Fraction of the celestial dome covered by the cloud layer 



reported by Symbol C 



Notes 



1. "Fragments of clouds" are coded as 1. 



2. "Overcast but with openings" is coded as 7. 



3. The full International specification for code figure 9, is "Sky obscured or 

 cloud amount cannot be estimated owing to darkness." 



15 



