A weather radar (also called Doppler radar) emits pulses of microwave energy and analyses the signals reflected back by precipitation particles — raindrops, hailstones, and snowflakes. By measuring the intensity of the return signal (reflectivity, in dBZ), the radar estimates precipitation rate and type. Doppler capability adds velocity information, revealing wind patterns within storms, including the rotational signatures of tornadoes and mesocyclones.
Modern radar networks — such as Spain's 15-radar AEMET network or the US NEXRAD system of 159 radars — provide composite images updated every 5–10 minutes, covering vast areas with remarkable detail. Dual-polarisation technology (sending both horizontal and vertical pulses) can distinguish between rain, snow, hail, and even non-meteorological targets like birds or insects. Radar data feeds directly into nowcasting (0–6 hour forecasts) and severe weather warnings.
For the general public, radar imagery — accessible on apps and websites like Meteo.es — is one of the most intuitive weather tools: the colour scale shows precipitation intensity (green = light, yellow = moderate, red = heavy, purple = extreme). Animations reveal the direction and speed of storm movement, allowing anyone to estimate when rain will arrive. Limitations include ground clutter (false echoes from buildings and terrain), beam overshooting (missing low-level precipitation at long range), and attenuation (heavy rain weakening the signal beyond). Despite these, weather radar remains the single most important tool for short-range precipitation forecasting and severe storm detection.