Table B-1. Present Weather Elements in the TMY2 Format
Field
Position

Element

Values

Definition
114

  Observation Indicator   0 or 9   0 = Weather observation made
  9 = Weather observation not made, or missing
115
















  Occurrence of
  Thunderstorm,
  Tornado, or Squall














0 - 2, 4,
6 - 9















  0 = Thunderstorm-lightning and thunder.
      Wind gusts less than 25.7 m/s, and hail, if
      any, less than 1.9 cm diameter
  1 = Heavy or severe thunderstorm-frequent
      intense lightning and thunder. Wind gusts
      greater than 25.7 m/s and hail, if any, 1.9
      cm or greater diameter
  2 = Report of tornado or waterspout
  4 = Moderate squall-sudden increase of wind
      speed by at least 8.2 m/s, reaching 11.3 m/s
      or more and lasting for at least 1 minute
  6 = Water spout ( beginning January 1984 )
  7 = Funnel cloud ( beginning January 1984 )
  8 = Tornado ( beginning January 1984 )
  9 = None if Observation Indicator element
      equals 0, or else unknown or missing if
      Observation Indicator element equals 9
116















  Occurrence of Rain,
  Rain Showers, or
  Freezing Rain













0 - 9















  0 = Light rain
  1 = Moderate rain
  2 = Heavy rain
  3 = Light rain showers
  4 = Moderate rain showers
  6 = Light freezing rain
  7 = Moderate freezing rain
  8 = Heavy freezing rain
  9 = None if Observation Indicator element
      equals 0, or else unknown or missing if
      Observation Indicator element equals 9

  Notes:
  Light = up to 0.25 cm per hour
  Moderate = 0.28 to 0.76 cm per hour
  Heavy = greater than 0.76 cm per hour
117





















  Occurrence of Rain
  Squalls, Drizzle, or
  Freezing Drizzle



















0, 1,
3 - 9




















  0 = Light rain squalls
  1 = Moderate rain squalls
  3 = Light drizzle
  4 = Moderate drizzle
  5 = Heavy drizzle
  6 = Light freezing drizzle
  7 = Moderate freezing drizzle
  8 = Heavy freezing drizzle
  9 = None if Observation Indicator element
      equals 0, or else unknown or missing if
      Observation Indicator element equals 9

  Notes:
  When drizzle or freezing drizzle occurs with
   other weather phenomena:
       Light = up to 0.025 cm per hour
       Moderate = 0.025 to 0.051 cm per hour
       Heavy = greater than 0.051 cm per hour
  When drizzle or freezing drizzle occurs alone:
       Light = visibility 1 km or greater
       Moderate = visibility between 0.5 and 1 km
       Heavy = visibility 0.5 km or less
118















  Occurrence of Snow,
  Snow Pellets, or Ice
  Crystals













0 - 9















  0 = Light snow
  1 = Moderate snow
  2 = Heavy snow
  3 = Light snow pellets
  4 = Moderate snow pellets
  5 = Heavy snow pellets
  6 = Light ice crystals
  7 = Moderate ice crystals
  8 = Heavy ice crystals
  9 = None if Observation Indicator element
      equals 0, or else unknown or missing if
      Observation Indicator element equals 9

  Notes:
  Beginning in April 1963, any occurrence of ice
  crystals is recorded as a 7.
119










  Occurrence of Snow
  Showers, Snow
  Squalls, or Snow
  Grains







0 - 7, 9










  0 = Light snow
  1 = Moderate snow showers
  2 = Heavy snow showers
  3 = Light snow squall
  4 = Moderate snow squall
  5 = Heavy snow squall
  6 = Light snow grains
  7 = Moderate snow grains
  9 = None if Observation Indicator element
      equals 0, or else unknown or missing if
      Observation Indicator element equals 9
120












  Occurrence of Sleet,
  Sleet Showers, or Hail











0 - 2,
4, 9











  0 = Light ice pellet showers
  1 = Moderate ice pellet showers
  2 = Heavy ice pellet showers
  4 = Hail
  9 = None if Observation Indicator element
      equals 0, or else unknown or missing if
      Observation Indicator element equals 9

  Notes:
  Prior to April 1970, ice pellets were coded as
  sleet. Beginning in April 1970, sleet and small
  hail were redefined as ice pellets and are coded
 as 0, 1, or 2.
121















  Occurrence of Fog,
  Blowing Dust, or
  Blowing Sand













0 - 9















  0 = Fog
  1 = Ice fog
 2 = Ground fog
 3 = Blowing dust
 4 = Blowing sand
 5 = Heavy fog
 6 = Glaze (beginning 1984)
 7 = Heavy ice fog (beginning 1984)
 8 = Heavy ground fog (beginning 1984)
 9 = None if Observation Indicator element
   equals 0, or else unknown or missing if
   Observation Indicator element equals 9

 Notes:
 These values recorded only when visibility is
   less than 11 km.
122














  Occurrence of Smoke,
 Haze, Smoke and
 Haze, Blowing Snow,
  Blowing Spray, or
 Dust










0 - 7, 9














  0 = Smoke
  1 = Haze
  2 = Smoke and haze
  3 = Dust
  4 = Blowing snow
  5 = Blowing spray
  6 = Dust storm (beginning 1984)
  7 = Volcanic ash
  9 = None if Observation Indicator element
      equals 0, or else unknown or missing if
      Observation Indicator element equals 9

  Notes:
  These values recorded only when visibility is
  less than 11 km.
123





  Occurrence of Ice
  Pellets




0 - 2, 9





  0 = Light ice pellets
  1 = Moderate ice pellets
  2 = Heavy ice pellets
  9 = None if Observation Indicator element
      equals 0, or else unknown or missing if
      Observation Indicator element equals 9



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