How to Graph Weather Patterns

Find a source of weather data. This may be your own observations: You can collect a wealth of empirical information with simple equipment, like outdoor thermometers, barometers, anemometers (which measure wind speed) and the like. Another good method is to tap the vast material from the National Weather Service available online or from television, radio or newspaper weather reports. Authoritative sources, like the National Weather Service or some university departments now include archives of weather information going back decades.

Bear in mind the distinction between ̶0;weather̶1; and ̶0;climate,̶1; terms often erroneously used interchangeably. Weather means the given atmospheric conditions of the moment in a particular location: a rainstorm, a heat wave, an emerging cyclone. Climate encompasses the long-term pattern of weather conditions for a certain region. Graphing weather activity over time helps quantify a climatic profile. While scientists are often more concerned with climate, the typical layperson planning his or her daily schedule might care most about the weather forecast for the next 12 hours.

Choose the variables that interest you. You may be concerned with temperature, for example. To examine the daily undulations of temperature at a given location, you̵7;d seek out absolute temperature values for certain times of day. But for examinations over the longer term ̵1; analyses of climate ̵1; you̵7;ll likely be working with mean temperature values or extreme maximums and minimums. Other commonly used weather factors include atmospheric pressure; precipitation amounts; relative humidity values; wind speed and direction.

Plot these variables against one another, time, location or any other factor. You might compare the maximum and minimum temperatures for a day (or a year) at different points to examine the influence of geography and topography on climate. For example, a city on the coast of an ocean or large lake ̵1; like San Francisco, California or Milwaukee, Wisconsin ̵1; will usually show less variable temperatures than one farther inland, away from the moderating influence of a big body of water.

Track atmospheric disturbances through graphs of weather patterns. Considering atmospheric pressure ̵1; roughly, the weight of overlying air at a given point ̵1; over time can reveal the arrival of a volatile low-pressure system that might prompt heavy rainfall, violent thunderstorms or even tornadoes. A plunge in the barometer often precedes the onset of such a storm. Less important than the actual pressure readings is their pattern over time. A rapid transformation of wind direction or speed might be another clue, especially when considered in the context of barometric change.