Weather radar is a tool for understanding atmospheric conditions and predicting precipitation. It uses various colors to represent different intensities of rain, snow, or hail. Interpreting these colors helps understand current weather conditions.
Understanding Red on Weather Radar
Weather radar systems operate by emitting microwave pulses into the atmosphere. These pulses interact with precipitation particles, such as raindrops or snowflakes, and a portion of the energy reflects back to the radar receiver. This returned energy is known as reflectivity, which meteorologists measure in units called decibels of Z (dBZ).
The color red on a weather radar display signifies the highest levels of reflectivity. A typical color scale progresses from blues and greens for light precipitation, to yellows and oranges for moderate precipitation, and then to reds and purples for very heavy or severe conditions.
Higher dBZ values correspond to stronger signals returned to the radar. For instance, light rain typically registers around 20 dBZ, while values exceeding 45 dBZ indicate intense precipitation. Red hues on the radar show these elevated dBZ values, occurring when precipitation particles are larger or more numerous, reflecting more energy back to the radar.
Specific Weather Phenomena Indicated by Red
When red appears on weather radar, it commonly indicates heavy rainfall. This can involve torrential downpours where rain falls at rates exceeding two inches per hour, significantly reducing visibility and making driving difficult. Such intense rainfall can quickly overwhelm drainage systems, leading to rapid street and yard flooding.
Red colors are also associated with strong thunderstorms, which may contain high winds and lightning. Very dark red or purplish hues on radar can signify the presence of large hail, as hail is highly reflective and produces very high dBZ values.
While red on reflectivity radar indicates strong precipitation, other radar products detect different phenomena. For example, Doppler radar measures the motion of precipitation particles, helping meteorologists identify rotating air masses or potential tornadoes. Reflectivity radar primarily shows precipitation intensity, not wind rotation.
Safety and Action When Red Appears
Seeing red on weather radar should prompt immediate safety considerations. Take any associated weather warnings seriously. If red areas are approaching your location or are overhead, seek shelter in a sturdy building.
When indoors during severe weather, stay away from windows and move to an interior room, basement, or the lowest floor for additional protection. During heavy rainfall indicated by red, avoiding travel is prudent, as reduced visibility and flooded roads create hazardous conditions. If encountering floodwaters, remember the guidance “Turn Around, Don’t Drown.”
Consult official sources, such as the National Weather Service or local meteorologists, for specific warnings related to severe thunderstorms or tornadoes that may accompany red radar returns. Have an emergency kit ready and secure loose outdoor objects to prepare for severe weather.