Station Weather Plot

station weather plotA station weather plot is a graphical representation of the weather conditions at a given time and location, either on land or at sea from a ship, platform, moored buoy or drifting buoy. It enables a large amount of automatically and manually observed data to be displayed in a very small space on a weather chart.

Weather charts are produced every day at regular intervals by national meteorological services, and comprise the station weather plots from many locations with a common observation time. The weather charts are then analysed by a meteorologist to determine the pressure pattern (e.g. the weather map shown on TV) and to look for trends in the plotted weather elements as one stage of preparing weather forecasts and warnings.

The data presented on weather charts are extracted from coded messages and then plotted as either raw values, encoded values, code figures or weather symbols. The meteorological data from land-based observing stations are traditionally distributed globally in coded SYNOP messages, whilst the data from ships and other marine platforms are distributed in other international code forms.

Raw & Encoded Values

The raw values of air temperature, dew point, maximum temperature and minimum temperature are plotted to one decimal place in line with standard BoM practice.

The mean sea level pressure is coded in tenths of a hPa and plotted as three digits after omitting the thousands digit(s):

The amount of pressure change is coded in tenths of a hPa. An amount of less than 10.0 is plotted as two digits including a leading zero if necessary. An amount of 10.0 or more is plotted as three digits:

The rainfall is coded as three digits for plotting. An amount of less than 1.0 is coded in tenths of a mm and prefixed by 99. An amount of 1.0 or more is coded as the nearest whole number and prefixed by leading zeroes if necessary. Nil rainfall is not coded:

The wind gust is coded as the nearest whole number then prefixed by G for plotting:

Layout & Decode

station weather plot layout guide

The layout of our station weather plot is shown above. It differs from the standard WMO station weather plot in regards to the positioning of amount of lowest cloud and the base of lowest cloud, and also the inclusion of wind gust as implemented by some national meteorological services.

Be aware that in the Southern Hemisphere the wind barbs are drawn to the right of the wind direction indicator, which is different to the Northern Hemisphere where the wind barbs are drawn to the left of the wind direction indicator.

Our minimum temperature and maximum temperature are manually reported, and only plotted with observations timestamped between 09:00 to 11:59 and 18:00 to 20:59 respectively.

Elements are omitted from the station weather plot in the following circumstances:

Refer to Weather Symbols & Code Figures for help deciphering the elements in the station weather plot.

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