The National Weather Service (NWS) has nearly completed a major modernization program to improve the quality and reliability of its products and services. One important key to the modernization is the new Doppler weather surveillance radar (Model WSR-88D). The WSR-88D (also known as NEXRAD) excels in detecting the severe weather events that threaten life and property, from early detection of damaging winds to estimating rainfall amounts for use in river and flood forecasting.
The WSR-88D uses Doppler radar technology to:
The WSR-88D capabilities will also:
- Substantially increase tornado warning lead time.
- Improve the detection and measurement of damaging winds, severe turbulence, wind shear and hail storms.
- Improve the forecast of the location and severity of thunderstorms.
- Increase the accuracy of identifying areas that are threatened.
- Substantially reduce the number of incorrect forecasts and false alarms.
- Increase the accuracy of rainfall estimates for flash flood warnings.
- Improve water resource management and river flood forecasts.
How Doppler Radar Sees Into the Future
Radar detects the presence and location of an object by bouncing an electromagnetic signal off of it and measuring the time it takes for the signal to return. This measurement is used to determine the distance and direction of the object from the radar. In the case of radar meteorology, the "objects" being measured are the particles of water, ice or dust in the atmosphere.Doppler radars take additional advantage of the fact that radar signals reflected from a moving object undergo a change in frequency related to the speed of the object traveling to or away from the radar antenna. Therefore, using Doppler technology, the WSR-88D calculates both the speed and direction of motion of severe storms. By providing data on the wind patterns within developing storms, the new WSR-88D can often identify the conditions leading to severe weather. A developing tornado, for example, can often be detected forming thousand of feet above the earth before it reaches the ground. This can be an important tool in the early detection of the precursors to tornadoes, as well as data on the direction and speed of tornadoes once they form.