Marine Glossary

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weather map

In meteorology, any map (sometimes called charts) on which data and analysis are presented that describe the state of the atmosphere or sea state over a large area at a given moment of time. They are made for the surface and for numerous other specific alayers in the atmosphere. For marine weather, we care primarly about surface data and data at 500 mb.

The standard surface analysis map shows the distribution of sea-level pressure (therefore, the positions of Highs, Lows, ridges, and troughs) and the location and nature of fronts and air masses.

Often added to this are symbols of occurring weather phenomena, analysis of pressure tendency (isallobars), indications of the movement of pressure systems and fronts, and possibly others depending upon the intended use of the chart. Although the pressure is referred to mean sea level, all other elements on this chart are presented as they occur at the surface point of observation. A chart of this general form is the one commonly referred to as the "weather map."

See Resources section of the Weather Trainer, Weather Map Atlas (G455) and Symbols Atlas (G301) for a complete list of weather symbols. The station model is shown in G308. See G176 for the synoptic code used in ship observations reported back to the weather services.

See G440 for a schematic presentation of how a weather map evolves, which is discussed in ART-22.

See also long-term forecast.

See also 500 mb map, as illustrated in G401 and G402 which is called a "tropics map."

Note that the NWS calls these products "charts" in some areas of their web site, and "maps" in other areas. Our preference is for maps, since charts has a specific meaning in nautical science.