May 18, 2006 6:00 am US/Eastern
May 18 Weather Trivia Answer
Correct Answer: National Weather Service
Via the National Weather Bureau Organic Act of 1890, the National Weather Service is the responsible agent for the forecasting of weather, the issue of storm warnings and the display of weather and flood signals for the benefit of agriculture. The National Weather Service uses many sources of data when developing its flood forecasts. The U.S. Geological Survey is the principal source of data on river depth and flow. The USGS operates and maintains more than 85% of the Nation's stream-gaging stations. This network is comprised of 7,292 stations throughout the nation which are equipped with earth satellite radios for communication. The NWS uses data from many of these stations to forecast river depth and flow conditions. The two most fundamental items of hydrologic information about a river are stage, which is the water depth above some arbitrary datum, commonly measured in feet, and flow or discharge, which is the total volume of water that flows past a point of time, usually measured in cubic feet per second or gallons per second. To create flood forecasts, the NWS develops and calibrates complex mathematical models of how the Nation's rivers and streams respond to rainfall and snowmelt. These models are developed for preselected forecast service points which are located along rivers and streams. In every case, records of discharge must be available so the NWS can create a river model. An important hydraulic input to thses models is the USGS stage/discharge rating. The resulting model is rarely exact, but it provides estimates of river response to rainfall..Thereafter, when heavy rainfall is forecast for the river basin, those amounts are entered into the model, and the model estimates the river stage and discharge that will result.
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