SYNOP CODE

WW Present weather (manned station)

WW=00-49     No precipitation at the station* at the time of observation

WW=00-19     No precipitation, fog,(except for 11 and 12), duststorm,
sandstorm, drifting or blowing snow at the station
at the time of observation  or, except for 09 and 17,
during the preceeding hour

      00     Cloud development not observed or observable }characteristic
      01     Clouds dissolving or becoming less developed }state of sky
      02     State of sky on the whole unchanged          }during the
      03     Clouds generally forming or developing       }past hour
      04     Visibility reduced by smoke haze
      05     Haze
      06     Widespread dust in suspension in the air, not raised by
wind at or near the station at the time of observation.
      07     Dust or sand raised by the wind at or near the station at
the time of the observation, but no well-developed dust
whirl(s), and no sandstorm seen: or, in the case of ships,
blowing spray at the station
      08     Well developed dust whirl(s) or sand whirl(s) seen
at or near the station during the preceding hour or
at the time of observation, but no duststorm or sandstorm
      09     Duststorm or sandstorm within sight at the time of
observation, or at the station during the preceding hour
      10     Mist
      11     Patches of               } shallow fog or ice fog
      12     More or less continuous } less than 2 m on land or 10 m at sea
      13     Lightning visible, no thunder heard
      14     Precipitation within sight, not reaching the ground or surface of sea
      15     Precipitation within sight, reaching ground or the
surface of the sea, but distant, i.e. estimated to
be more than 5 km from the station
      16     Precipitation within sight, reaching the ground or
the surface of the sea, near to, but not at the station
      17     Thunderstorm, but no precipitation at the time of observation
      18     Squalls                   } at or within sight of
) the station during
      19     Funnel cloud(s) or tuba¹ } the preceding hour or
) at time of observation

WW=20-29     Precipitation, fog, ice fog or thunderstorm at the station during
               the preceeding hour but not at the time observation

      20     Drizzle (not freezing) or snow grains }
      21     Rain (not freezing)                 }   Not
      22     Snow                                }   falling
      23     Rain and snow or ice pellets       }  as shower(s)
      24     Freezing drizzle or freezing rain  }
      25     Shower(s) of rain
      26     Shower(s) of snow, or of rain and snow
      27     Shower(s) of hail, or of rain and hail
      28     Fog or ice fog
      29     Thunderstorm (with or without precipitation)

WW=30-39     Duststorm, sandstorm, drifting or blowing snow

      30     }Slight or           {  has decreased during the preceding hour
      31     }moderate duststorm {  no appreciable change during the preceding hour
      32     }or sandstorm        {  has begun or increased during the preceding hour
      33     }Severe              {  has decreased during the preceding
      34     }duststorm           {  no appreciable change during the preceding hour
      35     }or sandstorm        {  has begun or increased during the preceding hour
      36     Slight or moderate drifting snow  }  Generally low
      37     Heavy drifting snow   }  (below eye level)
      38     Slight or moderate blowing snow }  Generally high
      39     Heavy blowing snow   }  (above eye level)            

WW=40-49     Fog or ice fog at the time of observation

      40     Fog or ice fog at a distance at the time of observation, but not at the
station during the preceding hour, the fog or ice fog extending to a
level above that of the observer
      41     Fog or ice fog in patches
      42     Fog or ice fog, sky visible   }  has become thinner during
      43     Fog or ice fog, sky obscured  }  preceding hour
      44     Fog or ice fog, sky visible   }  no appreciable change
      45     Fog or ice fog, sky obscured  }  during the preceding hour
      46     Fog or ice fog, sky visible   }  has begun or has become thicker
      47     Fog or ice fog, sky obscured  }  during the preceding hour
      48     Fog or ice fog, sky visible
      49     Fog or ice fog, sky obscured 

WW=50-59     Drizzle

      50     Drizzle, not freezing, intermittent }  slight at time
      51     Drizzle, not freezing, continuous   }  of observation
      52     Drizzle, not freezing, intermittent }  moderate at time
      53     Drizzle, not freezing, continuous   }  of observation
      54     Drizzle, not freezing, intermittent }  heavy (dense) at time
      55     Drizzle, not freezing, continuous   }  of observation
      56     Drizzle, freezing, slight
      57     Drizzle, freezing, moderate or heavy (dense)
      58     Drizzle and rain, slight
      59     Drizzle and rain, moderate or heavy

WW=60-69     Rain

      60     Rain, not freezing, intermittent   }  Slight at time
      61     Rain, not freezing, continuous     }  of observation
      62     Rain, not freezing, intermittent   }  Moderate at time
      63     Rain, not freezing, continuous     }  of observation
      64     Rain, not freezing, intermittent   }  Heavy at time
      65     Rain, not freezing, continuous     }  of observation
      66     Rain, freezing, slight
      67     Rain, freezing, moderate or heavy
      68     Rain or drizzle and snow, slight
      69     Rain or drizzle and snow, moderate or heavy 

WW=70-79     Solid precipitation not in showers

      70     Intermittent fall of snowflakes    }  slight at time
      71     Continuous fall of snowflakes      }  of observation
      72     Intermittent fall of snowflakes    }  moderate at time
      73     Continuous fall of snowflakes      }  of observation
      74     Intermittent fall of snowflakes    }  heavy at time
      75     Continuous fall of snowflakes      }  of observation
      76     Diamond dust (with or without fog)
      77     Snow grains (with or without fog)
      78     Isolated star-like snow crystals (with or without fog)
      79     Ice pellets                                          

WW=80-99     Showery precipitation, or precipitation with
               current or recent thunderstorm

      80     Rain shower(s), slight
      81     Rain shower(s), moderate or heavy
      82     Rain shower(s), violent
      83     Shower(s) of rain and snow mixed, slight
      84     Shower(s) of rain and snow mixed, moderate or heavy
      85     Snow shower(s), slight
      86     Snow shower(s), moderate or heavy
      87  }  Shower(s) of snow pellets or small hail            }- slight
      88  }    with or without rain or rain and snow mixed      }- moderate or heavy
      89  }  Shower(s) of hail, with or without rain or         }- slight
      90  }    rain and snow mixed, not associated with thunder }- moderate or heavy

WW=91-94     Thunderstorm during the preceeding hour
               but not at time of observation

      91     Slight rain at time of observation
      92     Moderate or heavy rain at time of observation
      93     Slight snow, or rain and snow mixed, or hail² at time of observation
      94     Moderate or heavy snow, or rain and snow mixed, or hail¹
at time of observation

WW=95-99    Thunderstorm at time of observation

      95      Thunderstorm, slight or moderate, without hail² but
with rain and or snow at time of observation
      96     Thunderstorm, slight or moderate, with hail²
at time of observation
      97     Thunderstorm, heavy, without hail² but with rain and
or snow at time of observation
      98     Thunderstorm combined with duststorm or sandstorm
at time of observation
      99     Thunderstorm, heavy,  with hail² at time of observation

* The expression at the station refers to a land station or a ship             

1 Tornado cloud or waterspout                                                  
2 Hail, small hail, snow pellets