In this mode, the radar is in its most sensitive operation. Velocity Azimuth Display (VAD) Wind Profile.Vertically Integrated Liquid Water (VIL).Included in the NEXRAD data are the following products, all updated every 6 minutes if the radar is in Precipitation Mode or every 10 minutes if the radar is in Clear Air Mode (continue scrolling for further definitions) However, light rain, light snow, or drizzle from shallow cloud weather systems are not necessarily detected. The National Weather Service's 148 WSR-88D Doppler radars can detect most precipitation within approximately 90 mi of the radar, and intense rain or snow within approximately 155 mi. This ability to 'see' the wind is what enables the National Weather Service to detect the formation of tornados which, in turn, allows us to issue tornado warnings with more advanced notice. Information on the movement of objects either toward or away from the radar can be used to estimate the speed of the wind. The radar's computers measure the frequency change of the reflected pulse of energy and then convert that change to a velocity of the object, either toward or from the radar. The same effect takes place in the atmosphere as a pulse of energy from NEXRAD strikes an object and is reflected back toward the radar. The faster the train moves, the greater the change in the whistle's pitch as it passes your location. Likewise, as the train moves away from you, the sound waves are stretched, lowering the pitch of the whistle. As the train approaches, the sound waves that make up the whistle are compressed making the pitch higher than if the train was stationary. You have most likely experienced the 'Doppler effect' around trains.Īs a train passes your location, you may have noticed the pitch in the train's whistle changing from high to low. This Doppler effect was named after the Austrian physicist, Christian Doppler, who discovered it. The frequency of the returning signal typically changes based upon the motion of the raindrops (or bugs, dust, etc.). The ability to detect the 'shift in the frequency' of the pulse of energy makes NEXRAD a Doppler radar. Computers analyze the strength of the returned radar waves, time it took to travel to the object and back, and frequency shift of the pulse. This reflected signal is then received by the radar during its listening period. A small portion of that scattered energy is directed back toward the radar. The radar emits a short pulse of energy, and if the pulse strike an object (raindrop, snowflake, bug, bird, etc), the radar waves are scattered in all directions. NEXRAD ( Next Generation Radar) can measure both precipitation and wind. In addition, the radar image will not show echos from precipitation that lies outside the radar's beam, either because the precipitation is too high above the radar, or because it is so close to the Earth's surface that it lies beneath the radar's beam. To determine if precipitation is occurring at greater distances, link to an adjacent radar. This image will not show echoes that are more distant than 143 miles, even though precipitation may be occurring at these greater distances.

The maximum range of the base reflectivity product is 143 miles (230 km) from the radar location. Base reflectivity images are available at several different elevation angles (tilts) of the antenna the base reflectivity image currently available on this website is from the lowest 'tilt' angle (0.5°).

'Reflectivity' is the amount of transmitted power returned to the radar receiver after hitting precipitation, compared to a reference power density at a distance of 1 meter from the radar antenna. The Local Radar base reflectivity product is a display of echo intensity (reflectivity) measured in dBZ (decibels). Precipitation intensity is measured by a ground-based radar that bounces radar waves off of precipitation.

Lightning tracker massachusetts