How to Read a Surface Weather Map

Meteorologists use surface weather map plots to determine what the weather is currently doing.

Weather maps appear on TV, the Internet and in newspapers. "Surface" weather maps contain a series of symbols, called plots, which allow meteorologists to describe what is going on at any particular time at a specific weather station. Meteorologists use many symbols for a variety of weather elements such as snow, rain, thunder and lightning. To read a surface weather map, you must know what those symbols are and their plot positions.

Things You'll Need

• Weather map

Instructions

Identifying the Symbols

1. 

   Surface weather plots indicate cloud positions.

   Read the top row on the left of the station weather plot; the first number is the temperature in degrees Fahrenheit. The center symbol depicts cloud cover; cirrus, nimbus, cumulus or stratus. The top symbol is the high cloud level, the one below it is the middle level and the third level, which includes a number showing the height of the cloud from its base point, indicates a lower cloud. The atmospheric pressure plot symbol is on the far right.

2. 

   Symbols like these indicate snowflakes falling.

   Read the second (middle) row of the plot. The far left number determines the visibility in miles. Next to that is a weather symbol; one of 95 that describe what the weather is doing currently or has done within the hour. For instance, several asterisks positioned in different ways describe how snow is falling. The circle symbol that is in the center of the middle row depicts the total amount of cloud cover. The number on the far right of the weather plot's middle row tells the meteorologist how much the atmospheric pressure has changed over the past three hours.

3. Read the third (bottom row) of the weather plot. Lines that resemble a tilted, upside down "F" represent the speed of the wind and its direction. These lines are attached to the sky-cloud cover circle symbol on the second row, indicating how fast and in what direction the wind is blowing. The number underneath the wind lines on the lower left of the weather plot is the dewpoint temperature, which determines air saturation for humidity. The lower right section of the plot shows previous weather conditions.

Reading the Map

1. Analyze the weather map. Meteorologists often do this by drawing constant pressure lines (called isobars), temperature points (called isotherms) and dewpoint measurements (called isodrosotherms). These pressure lines determine the current state of the atmosphere.

2. View the weather elements on the weather station plot in addition to the National Weather Service's radar color system. A tornado warning, for example, is bright red; the stronger the weather system, the brighter and more intense the element's color is.

3. Read the lines on the map. Typical weather maps have colored lines with arrows that determine high or low pressure and in what direction a cold or warm front is moving. High pressure systems usually mean fair weather; low pressure systems often bring storms and rain. Cold fronts bring cooler temperatures and warm fronts often bring warmer temperatures that could turn snow into rain with some fog thrown into the mix.

References

• National Weather Service: Jetstream-Online School for Weather: How to Read 'Surface' Weather Maps
• National Weather Service: Jetstream-Online School for Weather: Clouds
• National Weather Service: Jetstream-Online School for Weather: Surface Weather Plot Symbols
• National Weather Service: FAQs: Warnings, Watches and Colors
• The Weather Channel: How to Read a Surface Map

Resources

• National Weather Service JetStream - Online School for Weather
• National Oceanic and Atmospheric Administration
• National Weather Service
• The Weather Channel