How to Read a Weather Map

How to Read a Weather Map
When I was a child, my father worked as a flight service briefer. In the days before computers, flight service briefers took data gathered by the National Weather Service, along with short-term forecasts, and presented the information to pilots according to their flight plans. In this way, the pilot would know what kind of weather to expect during his or her journey. I was already interested in meteorology at that time, so sometimes I was able to go to work with my dad. I became familiar with the teletype machines, which printed data from weather stations all around the country onto long sheets of yellow paper. I also got to know the giant map of the United States spread across one wall of the room. It was covered with a sheet of Plexiglas, and my dad used a wax pencil to draw the symbols for surface fronts, isobars, and station reports on it.

Today’s maps are computer generated and much more sophisticated. There are many different types of maps. For example, The Weather Channel® offers current weather, Doppler radar, forecasts, satellite, regional, and international maps. Radar and combination radar/satellite maps are generally color-coded with green indicating rain (intensity of rain increases as color changes to yellow, orange, red, and sometimes purple), white for snow, and pink for ice.

Standard symbols have been developed for use on weather maps that show current weather and forecasts. Curved lines on the map connect points with the same barometric pressure. If these lines, called isobars, are close together, the areas they cover are likely to have strong winds. Isobars also indicate the “sphere of influence” of a low-pressure area. Lows are associated with clouds, rain, and storms. For individuals with pressure-affected illnesses such as arthritis, a low may also be associated with worsening of the symptoms.

A low pressure center is symbolized on the map by a large letter L, sometimes red in color. Its counterpart, the high pressure center, is shown by a large letter H, which may be blue. High pressure areas, unlike low pressure, are not associated with surface fronts. However, most low pressure centers will have one or more fronts attached to them. A front may be cold, warm, stationary, or occluded, and there are separate symbols for each, as illustrated in the chart below.

Synoptic weather maps, which may be obtained from the National Weather Service and other professional outlets, present data gathered from weather stations around the country. Each station is represented by a set of symbols and numbers:

This station model provides a systematic method of representing the current weather conditions at any given location. Meteorologists use the raw data on synoptic maps to assess weather patterns and identify isobars, frontal boundaries, and other atmospheric structures.

For more information on synoptic maps, please visit the links below.

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