Weather Symbols
Weather symbols are plotted on a synoptic chart used for weather forecasting, and show the position of weather stations collecting information about the weather, and details of the various weather elements. The position of a meteorological station is marked by a small circle. The weather report for each station is then plotted in and around the circle. Elements like temperature and pressure are entered as plain figures. Others, like the occurrence of rain, snow, cloud and fog are plotted as internationally agreed symbols. For example cloud cover at a particular time is indicated by filling in certain portions of the circle. The greater the fill, the more the cloud cover, measured in eighths or oktas. Wind direction is represented by an arrow pointing in the direction from where the wind is coming. The wind speed is denoted by "feathers" on the wind arrow, a short feather indicating 5 knots, a larger one 10 knots, a long and short one 15 knots and so on.
Temperature is measured in degrees Celsius to the nearest whole degree. Pressure at a station is standardised to sea-level pressure measured in millibars. Sometimes the hundreds figure for the pressure is omitted as being understood since the pressure is almost always between 950 and 1050 millibars. For example, a pressure of 987.8 millibars would be written as 878; 1014.3 millibars as 143.
|
