Weather Mapping

Many different kinds of weather maps exist. Synoptic maps show current weather conditions, while prognostic maps show weather predictions for some time in the future. Some weather maps are complex and contain a great deal of detailed information. Others are simpler and provide only general patterns and trends. Maps can be sub-divided into those that summarize weather close to Earth's surface (surface charts) and those that describe weather at upper altitudes.

One very detailed type of map makes use of the station model. The reporting station is indicated with a small circle and the data received from that station is arranged around the circle in a predetermined pattern. Among the kinds of data plotted in the station model are cloud cover, wind direction, visibility in miles, present weather, barometric pressure, current air temperature, cloud types, dew point, and precipitation.

Most of these variables can be represented by numbers. Visibility might be indicated as 1/2 for 0.5 mi (0.8 km) and current temperature as 22 for 22°C (71°F). Other data are represented by standard symbols. Wind direction and speed are indicated by a one-edged arrow. The number of feathers on the arrow indicate the wind speed and the orientation of the arrow indicates the wind direction. A single full feather represents a wind speed of 8-12 knots; a double feather, a speed of 18-22 knots; and so on. A variety of symbols represent current weather conditions, such as * for intermittent snow fall and ⁺, for intermittent drizzle.