What Is Weather Radar?
Weather radar, or Doppler radar, is one of the most powerful tools for tracking precipitation and severe weather in real time. Radar works by sending out pulses of microwave energy that bounce off precipitation particles like rain, snow, hail, and sleet. By measuring the returned signal, meteorologists can determine the location, intensity, and movement of precipitation.
The National Weather Service (NWS) operates a network of 160 WSR-88D Doppler radar stations across the United States, providing nearly complete coverage of the country. These radars update every 4-10 minutes, giving you a near real-time view of weather conditions.
Understanding Radar Colors
Radar images use a color scale to represent the intensity of precipitation, measured in dBZ (decibels of reflectivity). Here is what each color typically means:
Light Precipitation (Green Shades)
Green colors indicate light precipitation. Light green shows drizzle or very light rain (5-20 dBZ), while darker green indicates light to moderate rain (20-30 dBZ). You might need an umbrella, but conditions are generally safe for travel.
Moderate Precipitation (Yellow to Orange)
Yellow represents moderate rain (30-40 dBZ), and orange shows heavy rain (40-50 dBZ). At these levels, visibility can be reduced and roads may become slick. Pay attention to changing conditions and consider delaying travel if patterns are intensifying.
Heavy Precipitation (Red to Purple)
Red indicates very heavy rain or hail (50-60 dBZ), while pink and purple represent extreme precipitation (60+ dBZ). These colors signal dangerous conditions including possible severe thunderstorms, large hail, flash flooding, and tornadoes. Seek shelter immediately when you see these colors approaching your area.
Winter Precipitation Colors
Some radar displays use blue and pink colors to indicate frozen or mixed precipitation. Light blue may indicate snow, while pink can represent freezing rain or sleet. These interpretations depend on the specific radar product being viewed.
Reading Radar Patterns
Isolated Storms vs. Lines
Individual cells appearing as isolated blobs often represent pop-up thunderstorms common on summer afternoons. Linear patterns or squall lines indicate organized severe weather that can produce damaging winds, tornadoes, and heavy rain along a broad front.
Hook Echoes and Rotation
A hook-shaped pattern on radar is one of the most important signatures to recognize. Hook echoes often indicate a mesocyclone within a supercell thunderstorm and suggest a tornado may be forming or already on the ground. If you spot a hook echo near your location, take shelter immediately.
Bow Echoes
A bowed or curved line of storms often indicates a derecho or powerful windstorm. The apex of the bow is where the strongest winds occur, sometimes exceeding 100 mph. These systems can travel hundreds of miles and cause widespread damage.
Tips for Using Radar Effectively
Loop the radar animation to see storm movement and predict where precipitation will be in the next hour. Pay attention to storm trends — are they intensifying or weakening? Check radar before outdoor activities, especially during severe weather season from March through September.
On WeatherStream360, you can overlay radar data on the live map to see precipitation in the context of your location. Use the animation controls to loop recent radar frames and track storm movement.
Common Radar Artifacts
Not everything you see on radar is precipitation. Ground clutter near radar stations appears as a persistent blob. AP (anomalous propagation) can create false echoes in certain atmospheric conditions. Birds, insects, and even wind farms can produce radar returns. Learn to distinguish these artifacts from actual precipitation by comparing with satellite imagery.
Dual-Polarization Radar
Modern WSR-88D radars use dual-polarization technology, sending both horizontal and vertical pulses. This allows the radar to determine the size and shape of precipitation particles, improving the accuracy of precipitation type identification. Dual-pol radar is better at distinguishing between rain, snow, hail, and debris from tornadoes.