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.
University of North Dakota / School of Aerospace Sciences / Atmospheric Science Department
Contact the Webmaster with any problems.
