SYNOP CODE

SYNOP CODE

iiiiRixhVVNddff1snTTT2snTdTdTd3pppp4PPPP5appp6RRRtR7wwW1W28NhCLCMCH

3331snTxTxTx2snTnTnTn3EsnTgTg4E'sss8NsChshs9SpSpspsp

5551V'f'/V'f''f'2snTwTwTw

SECTION 0

                iiiiRixhVV

SECTION 1

                Nddff 1snTTT 2snTdTdTd 3pppp 4PPPP 5appp 6RRRtR 7wwW1W2 8NhCLCMCH

SECTION 3

333         1snTxTxTx (at 1800 UTC) 2snTnTnTn (at 0600 UTC)            3EsnTgTg (at 0600 UTC)

                4E'sss (at 0600 UTC) 8NsChshs 9SpSpspsp

SECTION 5

555         1V'f'/V'f''f'' 2snTwTwTw

Interpretation

SECTION 0

iii         Station Number

iRixhVViR      Inclusion or omission of precipitation data

ix      Inclusion or omission of weather group

h       Height of base of lowest cloud

            VV      Horizontal visibility

SECTION 1

Nddff       N       Total Cloud amount

dd      Wind direction in tens of degrees

ff      Wind speed in knots

1snTTT      1       Indicator

sn      Sign of temperature

            TTT     Dry-bulb temperature to the tenth of a degree Celsius

            (10302 = +30.2C)

2snTdTdTd   2       Indicator

sn      Sign of temperature

TdTdTd  Dew-point temperature to the tenth of a degree Celsius

            (20281 = +28.1C)

3pppp       3       Indicator

pppp    Station level pressure.  Rarely used now. Not used in a station plot.

4PPPP       4       Indicator

            PPPP    Last four figs. of air pressure (reduced to mean sea level) in millibars

and tenths (49882 = 988.2 mb)

5appp       5       Indicator

a       Characteristic of pressure change

ppp     Pressure change over last three hours in millibars and tenths

6RRRtR      6       Indicator

            RRR     Amount of rainfall

tR      Duration of period of RRR in units of six hours.  Main hours only

                    At 0001 and 1200 UTC tR=1   At 0600 and 1800 tR=2

7wwW1W2     7       Indicator

ww      Present weather, manned station

            W1W2    Past weather, manned station

8NhCLCMCH   8       Indicator

Nh      Amount of low cloud, or medium cloud if no low cloud present

            CL      Form of low cloud

            CM      Form of medium cloud

            CH      Form of high cloud

SECTION 3

333         Regional Indicator

1snTxTxTx   1       Indicator

sn      Sign of temperature

TxTxTx  Maximum temperature 0600-1800 UTC in tenths of a degree

2snTnTnTn   2       Indicator

sn      Sign of temperature

TnTnTn  Minimum temperature 1800-0600 UTC in tenths of a degree

3EsnTgTg    3       Indicator

            E       State of ground without snow or measurable ice cover

sn      Sign of temperature

TgTg    Grass minimum temperature rounded to nearest whole degree

4E'sss      4       Indicator

            E'      State of ground with snow or measurable ice cover

sss     Depth of snow

8NsChshs    8       Indicator

            Ns      Amount of individual cloud layer

            C       Form of cloud

hshs    Height of base of cloud layer

Up to four layers of significant cloud can be reported (using 8NhChshs groups).

The rules for the selection of significant cloud layers are:

                1.   The lowest layer of any amount

                2.   The next lowest layer of 3 oktas (eighths) or more.

                3.   The next lowest layer of 5 oktas or more.

                4.   Any cumulonimbus cloud not already reported under 1, 2 or 3 above,

regardless of amount.

Clouds are reported in order of ascending height.

Cumulonimbus cloud reported under rule 4 above would be inserted between the

other groups at its correct height level - regardless of the amount of

Cumulonimbus being reported.

9SpSpspsp       9       Indicator

                        This group is included when necessary to report special phenomena.

SECTION 5

555                         National indicator (This section is not sent when there are no data to report)

1V'f'/V'f''f''       1              Indicator

                                V'V'        Visibility in meters (reported when visibility is less than 100 m)

                                (f')f'f'     Speed in knots of the maximum gust in the past hour (>33 kts)

2snTwTwTw       2              Indicator

                                sn           Sign of temperature

                TwTwTw  Sea temperature in tenths of a degree

CODE TABLES

Table 1:iR  Indicator for inclusion or omission of precipitation data

Code

Figure   Precipitation data are reported:                Group 6RRRtR is:

1              in Section 1                                 included

2              in Section 3                                 included

3              in none of the two Sections 1 and 3         omitted (precipitation amount =0)

4              in none of the two Sections 1 and 3         omitted (precipitation amount not available)

Note:  UK practice only, code figures 1,3 and 4 to be used

Table 2:ix  Indicator for type of station operation (manned or automatic)

and for present and past weather

Code

figure    Type of station operation   Group 7wwW1W2 or 7wawaWa1Wa2 is:

1              manned                                   included

2              manned                                   omitted (no significant phenomena to report)

3              manned                                   omitted (not observed, data not available