Explains how to decode a synoptic observation, used by weather stations around the world.
A synop is a report of a surface observation from a land based station. A typical synop will have the following format:
AAAAA BCDEE FGGHH 1IJJJ 2KLLL 3MMMM 4NNNN 5OPPP 6QQQR 7SSSS 8TUVW ### .....
and can be decoded as follows:
AAAAA- Station's five digit identification number B- Indicator for inclusion or omission of precipitation data: 1 In section 1 (regional codes indicated by ###=111) 2 In section 3 (regional codes indicated by ###=333) 3 Precipitation amount=0 4 Precipitation amount not available C- Indicator for type of station operation: 1,2,3 Manned 4,5,6 Automatic D- Height above surface of the base of the lowest cloud seen: 0 0-50 meters 1 50-100 meters 2 100-200 meters 3 200-300 meters 4 300-600 meters 5 600-1000 meters 6 1000-1500 meters 7 1500-2000 meters 8 2000-2500 meters 9 2500 or more, or no clouds at all / Height at base of cloud not known or the base of the clouds is at a lower level and the tops are at a higher level than that of the station. EE- Horizontal visibility at the surface: For EE=00 to EE=50: visibility in tenths of kilometers (ex: 31=3.1km) For EE=56 to EE=80: visibility in kilometers + 50 (ex: 67=17km) 81 35km 86 60km 82 40km 87 65km 83 45km 88 70km 84 50km 89 >70km F- Total cloud cover in oktas (eights): 0 No cloud cover 1-8 Cloud cover in eights 9 Sky obscured by fog and/or other meteorological phenomena / Cloud cover is indiscernable for reasons other than fog or other meteorological phenomena, or the observation was not made. GG- True direction, in tens of degrees, from which the wind is blowing: Ex: 27=270 degrees (west wind) HH- Wind speed in meters per second: Ex: 13=13 meters per second (~ 26 mph) 1,2,3,4,5- Group number I- Sign of the following data: 0 Postive or zero 1 Negative JJJ- Temperature in tenths of degrees Celsius. Used in combination with "I": Ex: 0123= 12.3 degrees above zero 1034= 3.4 degress below zero K- Same as "I" LLL- Dew point temperature in tenths of degrees Celsius. Used the same as "JJJ". MMMM- Station pressure, not reduced to sea level: NNNN- Station pressure reduced to sea level: NNNN greater than 5000 Station pressure in tenths of millibars NNNN less than 5000 Add a preceding 1 to get the corrected surface pressure in tenths of millibars. Ex: 9872 = 987.2 millibars 0305 = 1030.5 millibars O- Pressure tendency during the three previous hours preceding the time of observation: 0 Increasing, then decreasing; atmospheric pressure the same or higher than 3 hours ago 1* Increasing, then steady; or increasing, then increasing more slowly 2* Increasing (steadily or unsteadily) 3* Decreasing or steady, then increasing; or increasing, then increasing more rapidly 4 Steady; atmospheric pressure the same as three hours ago 5 Decreasing, then increasing; atmospheric pressure the same or lower than three hours ago 6** Decreasing, then steady; or decreasing, then decreasing more slowly 7** Decreasing (steadily or unsteadily) 8** Steady or increasing, then decreasing; or decreasing, then decreasing more rapidly * indicates atmospheric pressure higher now than three hours ago ** indicates atmospheric pressure lower now than three hours ago PPP- Pressure rise or fall in tenths of millibars QQQ- Amount of precipitation which has fallen during the period preceding the time of observation, as indicated by "R": 000 Not used 001 1 mm 002 2mm (etc. up to 988) 989 989 mm or more 990 Trace 991 .1 mm 992 .2 mm (etc. up to 999 = .9mm) R- Time period for precipitation observation (not defined in WMO manual) SSSS- Indicators of past or present weather phenomena (refer to WMO manual for decoding procedure) T- Amount of the "U" cloud present, or if no "U" cloud is present, the amount of "V" cloud present: U- Clouds of the genera Stratocumulus, Stratus, Cumulus, or Cumulonimbus. V- Clouds of the genera Cirrus, Cirrocumulus, or Cirrostratus. W- Clouds of the genera Cirrus, Cirrocumulus, or Cirrostratus. For more information on the codes for "U", "V", and "W" refer to the WMO manual.
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