Extreme Weather

Background Information

16,367 DEAD / 45.2 BILLION DOLLARS IN DAMAGE WEATHER What YOU Can Do About It Cover: Life Magazine, August 1998

One of the ways we characterize our environment is by describing the weather or climate. Weather is the term that refers to the conditions of the atmosphere that we experience each day, while climate is the average of the day-to-day weather conditions over a long period of time. For example, using the terms arctic environment, temperate environment, or tropical environment gives us an idea as to the weather and general climate of a given area. When examining a particular environment we tend to look at averages such as annual precipitation, average temperatures, and average wind speed and direction. What we miss sometimes are the extremes. The extremes occur infrequently and may not affect the average very much. For example, a particular city’s average rainfall may be 50 inches per year, but one storm could drop 15 inches of rain and flood the city. When averaged over a ten or twenty year period, this unusual occurrence may not stand out. What we want to look at are extremes of weather or certain severe weather phenomena.

Climates in the U.S. include low desert, high desert, subtropics, tundra, and temperate zones. Blizzards, tornadoes, hurricanes, droughts, and flooding can occur in many locations, but these types of severe weather are more common in some areas than others. Even Death Valley, California, occasionally experiences flooding and in Miami, Florida, residents have experienced heavy snow. In 1997, flooding along the Red River heavily damaged North Dakota communities that hadn’t experienced such high water since they had been built. These unusual weather occurrences are labeled “50 year or 100 year events.” Such a designation doesn’t mean that unusual events will come along every 50 years; it means that statistically, an event would be expected to occur only once in every 50 years. For example, an event could happen twice in a decade—then 90 years could possibly pass before it happens again.

Because weather is so important to our lives, governments around the world spend considerable effort and money to monitor it. The collected data, gathered by thousands of weather stations around the globe, are placed in huge databases and used in a variety of ways. For example, a weather broadcaster would use these data when announcing that this was the hottest July 4th in the community since 1957. Meteorologists can estimate weather conditions on a given day and discover whether it rained under similar conditions in previous years. They can also use the data to produce climate models that provide better long-range forecasts.

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