Weather radar provides a visual map of precipitation by measuring how much energy is reflected back from water droplets, snowflakes, or hail. This measured return signal is called reflectivity, quantified in units of decibels of Z, or dBZ. The higher the dBZ value, the stronger the reflected signal, and the more intense the precipitation is. The general public relies on these color-coded maps to quickly assess the severity and location of approaching weather systems.
The Foundation of Radar Color Scales
The visual language of a weather radar map uses a standard progression of colors to represent increasing precipitation intensity. This scale begins with cooler colors, such as light blue or green, which signify very light rain or drizzle with low reflectivity values.
As precipitation intensity increases, the color transitions to warmer shades like yellow and orange. These colors indicate moderate to heavy rainfall. The scale is based on the logarithmic dBZ scale, meaning a small jump in the dBZ number represents a significant increase in the actual rainfall rate. The scale continues to intensify through various shades of red, marking very heavy rain and the potential for embedded thunderstorms.
Interpreting Extreme Reflectivity
The color pink or magenta on a weather radar map represents the highest possible reflectivity values, typically starting at 65 dBZ and above. This vibrant color is intentionally placed at the extreme end of the scale to signal a dangerous level of precipitation intensity.
The presence of pink or magenta indicates an exceptional amount of returned energy, resulting from two primary physical weather conditions. First, this extreme reflectivity can be caused by torrential rainfall rates, often exceeding several inches per hour, leading to a high risk of flash flooding. Second, this color strongly suggests the presence of very large precipitation particles, such as massive hailstones or dense, water-coated graupel.
Hailstones are highly effective at reflecting radar energy, causing the dBZ value to spike far beyond what is possible with even the heaviest rain. When the radar detects reflectivity in the pink range, it is an urgent warning that the storm is producing the most intense downpour or the largest hail. This color is a direct indicator of maximum intensity, demanding immediate attention and serving as a crucial technical marker for meteorologists.
Pink and Severe Weather Signatures
Because hail is an efficient reflector of radar energy, the pink or magenta color frequently outlines the core of severe thunderstorms where the largest hailstones are suspended by powerful updrafts. Reflectivity values in the 65 dBZ range and higher are often associated with hail the size of golf balls or larger.
In a severe storm, the pink region highlights the most violent section, which can sometimes reveal specific storm structures. For instance, the extreme reflectivity may be part of a “hook echo,” a distinct, curved shape on the radar that implies rotation within a supercell thunderstorm and a favorable environment for tornado development. The color’s location helps forecasters pinpoint the most dangerous part of the storm, which is often the area surrounding the intense updraft.
Seeing this color on the radar is an immediate call to action for safety. High-reflectivity cores indicate not only extremely strong winds and intense lightning but also the potential for damaging hail and flash floods. Immediate shelter should be sought when a storm showing pink or magenta is approaching, as the combination of particle size and precipitation rate poses a direct threat to life and property.