![]() NEXRAD determines the movement of wind-driven precipitation using a principle known as the "Doppler effect". Forecasters use other information at their disposal to make this determination. In addition, radar alone cannot determine if precipitation is rain or snow. The radar is so sensitive that it can detect clouds, dust and aerosol particles, insects, and birds, not to mention airplanes and ground based objects near the RDA itself. Unfortunately, the radar can display "echoes" that may or may not represent meteorological targets. The most common is a reflectivity image, which shows the areal extent of precipitation. The Advanced Weather Interactive Processing System (AWIPS) workstation, allows forecasters to display radar data(top picture). WEATHER RADAR DOPPLER GENERATORThe processing computer, known as the Radar Product Generator (RPG), performs various data quality checks of the raw radar data and creates radar images and products. The returned energy, called base data, is sent from the RDA site to the processing computer located here in the office(bottom picture). Part of the energy will be reflected back to the antenna, where the dish focuses the returned energy. When this energy hits an object, like a raindrop or snowflake, it is reflected in all directions. The transmitter at the antenna within this protective dome sends out a pulse of energy. The radar dish (pictured above) is protected by a covering that resembles a giant soccer ball. It all starts at the Radar Data Acquisition unit (RDA), which is the tower (pictured above) located adjacent to the forecast office. Radar requires three integral parts to work: (1) an antenna/receiver, (2) computers that process the raw radar data, and (3) an interactive workstation that the forecasters can use to display the processed radar data. The term WSR-88D is simple to explain: WSR stands for Weather Surveillance Radar 88 represents the year the first NEXRAD was commissioned for use (1988) and the D means it is a Doppler radar. Within the National Weather Service, NEXRAD is officially called the WSR-88D. In this way, the radar images can be shared with all interested groups. News agencies, television stations, military installations and other sites have access to the radar images through cooperation with the National Weather Service. Other common terms for weather radar are weather surveillance radar (WSR) and Doppler weather radar.The National Weather Service's Doppler radar, known as NEXRAD (for the NEXt generation of RADar), is the only Doppler weather radar on Long Island. Base Reflectivity images are available at several different elevation angles (tilts) of the antenna and are used to detect precipitation, evaluate storm structure, locate atmospheric boundaries and determine hail potential. "Reflectivity" is the amount of transmitted power returned to the radar receiver. The data can be analyzed to determine a storm's structure and the possibility they could become severe. A base reflectivity radar is a display of echo intensity (reflectivity) measured in dBZ (decibels of Z, where Z represents the energy reflected back to the radar). green is rain, pink is a mix of rain, freezing rain, sleet, and/or snow and blue is snow. The precipitation type is indicated by different colors. Why You Should Check The Local Weather Before Planning Your DayĪbout this map: The Precipitation Type Radar is the base reflectivity radar with areas of precipitation split into their respective precipitation types (rain, snow, hail, etc.). WEATHER RADAR DOPPLER HOW TOHow to Use the Tide Schedule to Your Advantage.The Surprising Way Weather Affects Your Mood. ![]()
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