SYNOPTIC OBSERVATIONS DECODING & PLOTTING

ENCODING WEATHER INFORMATION In order for people to send information around the world using the WMO discussed earlier the information has to be in a language understood by everyone around the world. In order to do this we encode the information into a series of numbers known as the “ SYNOP CODE ”.

SYNOP CODE / = Here is an example of a coded weather message;

The SYNOP code. Identifies which country the observation is from and which weather station. 03 means the UK. 535 means Birmingham /

The SYNOP code. Identifies a manned/unmanned weather station. Identifies lowest cloud base/visibility. 41 means the station is manned 4 means height of lowest cloud base using the “ h ” code 4 = 1000 – 2000 feet. 70 refers to minimum visibility using the VV code 70 = 20km /

8 identifies cloud cover in Oktas (eighths) using the N code 8 = total cloud cover. 23 identifies wind direction in tens of degrees,relative to true north 23 = 230°. 12 = Wind speed in knots. The SYNOP code / 82312

The SYNOP code 1 Identifies the dry bulb (air) temperature group. 0 indicates that value is above freezing 1 = below freezing. 077 Air temp in degrees and tenths (I.e. temp is +07.7°C) /

The SYNOP code. 2 Identifies Dew Point Temp group. 0 indicates temp is above freezing 1 = below freezing. Dew point temp in degrees and tenths (i.e. DP temp = °C) /

The SYNOP code 4 Identifies Mean Sea Level (Pressure) group Indicates MSL pressure is mb The 1 when plotting is not used when the pressure is greater than < 1000 mb. When the pressure is less than > 1000mb all four figures can be included, e.g would read (Generally pressure is between mb /

The SYNOP code 5 Identifier of the pressure tendency group. 8 The characteristic (the way the pressure has changed) over the past 3 hours. Using the A code. 012 Amount of change over the past 3 hours Is expressed in degrees and tenths (I.e. 01.2mb) /

The SYNOP code 7 Identifies Present and Past weather. 21Present weather using WW code means rain during the past hour(dph). (But it wasn ’ t raining at the time of the ob ’ s). 6 & 5 To be used individually & refer to weather from the past 6 hours. (Worst weather first). Using W1 W2 code 6 = past rain 5 = past drizzle /

The SYNOP code 8 Identifies the cloud data group 6 Amount of lowest cloud type in Oktas. (check with “ h ” figure in the 2 nd group). 8 Predominant low cloud. 8 = Cumulus and Stratocumulus. 2 Predominant medium cloud 2 = Dense Altostratus. / Predominant high cloud cannot be reported as it is obscured by lower cloud / 8682/

Present Weather Terms Precipitation means water droplets or ice particles, formed at a higher level and dropping to the ground. Continuous: Precipitation that has been falling continuously for at least 60 minutes, with no breaks. Intermittent: Precipitation that has been falling for at least 60 minutes, but there has been a break or breaks, or precipitation commenced less than 60 minutes ago. Showers: Precipitation that starts or stops abruptly, usually of short duration, often associated with bright periods between showers with good visibility.

Present Weather Terms At the station: At the place where observations are taken. Within sight or At a distance: Phenomena not occurring at the station, but occurring in the vicinity. During the past hour (dph): Phenomena occurring since the last observation, but NOT at the time of the current observation or a phenomena STOPS during the observation of present weather.

ENCODING OUR OBSERVATIONS Now we will encode our observations into the SYNOP Code.

Station Plots

Station plots are used to show large amounts of meteorological information in as small an area as possible to build up charts. The charts use simple symbols to show information The plot is based around one of two shapes. CIRCLES are for manual observations, TRIANGLES for automatic observations.

Station Plots High Cloud plotted in Red. Dew Point in Red. Pressure is plotted with the last 3 figures only, for example: is is 986 Falling pressure tendency in Red, steady or rising in Black. Sea temperature in Black Visibility in Red All others in Black.

The Station Circle. Black ink to be used unless otherwise stated. High Cloud C h Medium Cloud C m MSL Pressure pppp Pressure Tendency appp Past weather W1 W2 (Red ink if falling!) Low Cloud C L Amount of Low cloud / Height of Low cloud N h Dew Point TdTd Present weather ww Visibility vv Air Temp TT (Dry bulb) Wind speed/ direction Total Cloud In Okta’s N

Present Weather Symbols Present weather symbols are obtained from the synop code description of the weather. First number down the side second on the top. 56 (Slight freezing drizzle) =

Other Plotting Symbols Other plotting symbols are shown in a similar way. The code part is across the top with the code number on the left. Low cloud type 3 (Cb) would be

Station Circle / High Cloud Medium Cloud Pressure(MSL) 007 Past Weather Pressure tendency 012 Low Cloud 6/4 Wind speed/Direction Dew Point 064 Present Weather Visibility 70 Air temp Dry Bulb 077

Station Circle Completed. Wind 360° 25 Knots MSL Pressure Pressure change 1.6mb Pressure rising then falling Past weather Showers and rain Low cloud 5/8 Oktas Cumulonimbus 1000 – 2000ft Dew point 08.1° C Present weather Showers during past hour Air temperature 09.6°