Radar Maps and Animations - Map Viewer

NEXRAD Radar Data

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General

Radar technology enables weather observers to track rain and snow storms in real time. Radar is an object detection system that works by emitting radio waves and measuring the time it takes for them to return after they bounce off objects (such as raindrops or snowflakes) in the air. Weather forecast maps commonly use animations of radar data—color patterns representing the location and intensity of precipitation—to warn people of approaching storms.

How are these data collected?

NEXRAD (Next Generation Radar) stations obtain weather information (precipitation and wind) based upon reflected energy. The radar unit emits a burst, or pulse, of energy and records the location and magnitude of energy that is reflected back to the unit. When the energy pulse strikes an object (raindrop, snowflake, bug, bird, etc), the energy is scattered in all directions. A small fraction of the scattered energy is directed back toward the radar.

The radar instrument receives a signal from this reflected energy during its listening period. Computers analyze the strength of the returned pulse, the time it took to travel to the object and back, and the phase shift of the pulse. This process of emitting a signal, listening for any returned signal, then emitting the next signal, takes place very fast, up to around 1300 times each second. Doppler radars scan the horizon in 360˚ degrees in a set pattern of angles from very low (along the horizon) to very high (almost straight up). A complete set of scans takes around 5 minutes to complete. These scans are interpreted by a computer and translated into an image.

What can I do with these data?

  • Check the location and intensity of precipitation in past or current storms
  • View an animation of sequential radar images (singe frames are taken 5 minutes apart) to view the motion and evolution of past or current storms
  • Examine patterns of current storms to predict when rain or snow may arrive at a location