the United States are weather-related (Kelly, 2001). Weather affects aviation, air quality, health, ground and marine transportation, defense, agriculture, fisheries, water, energy, construction, tourism, and many other sectors of the economy. Even “good” weather can cause problems in this complex society; for example, one unexpectedly warm winter day in the Northeast can cost utility companies millions of dollars a day in unused energy.
There is also a growing awareness of the impact of climate variability and change, on time scales ranging from months to decades (NRC, 2001a). Shifts in rainfall patterns associated with climatic variability, such as those accompanying El Niño and La Niña, result in a nation and a world that is often plagued by drought and floods at the same time. Demand for climate data, information, and forecasts is growing rapidly, with NOAA’s National Climate Data Center (NCDC) receiving nearly 2 million online contacts from users in the year 2000, 77 percent from industry.1
As society becomes more sensitive to weather, the importance of weather prediction for the protection of lives and property and continued economic growth increases. For example, the U.S. population that resides within 50 miles of the nation’s coastlines and is most threatened by hurricanes and flooding is growing rapidly. Such population growth in these and other high-risk areas significantly increases the need for improved weather predictions and warnings to minimize risks to life and property. Another consideration is that the new economic concept of “just-in-time manufacturing” uses computer-timed and -directed supply systems to eliminate the warehousing of parts and products at ports and factories. However, even minor weather disruptions of land, sea, and air-supply-system pathways caused by snow, ice, and high-wind weather systems can now have large, leveraged impacts on these production systems, whereas previously they had little effect.
The last several decades have seen major advances in the scientific understanding of weather and climate, and these advances, enabled by observational and computer technologies, have led to major improvements in warnings of severe weather, in short- and medium-range weather forecasts, and in climate outlooks on time scales ranging from a month to a year or longer. For example, the warnings of flash floods, tornadoes, and severe thunderstorms by the National Weather Service (NWS) have been improving steadily over the past two decades (Figure 3.1).