The other scale (near left) represents the “storm relative motion” radial velocities. One scale (far left) represents radial velocities in the base velocity image. The transition zone between incoming and outgoing winds are indicated the gray-ish colors between the two.Įach velocity image includes one of two velocity scales regardless of the radar’s operation mode.

In velocity images, red colors indicated wind moving away from the radar with green colors indicating motion toward the radar. The colors are the different radial velocities measured by the radar. What do the colors mean in the velocity images? Since hail can cause the rainfall estimates to be higher than what is actually occurring, steps are taken to prevent these high dBZ values from being converted to rainfall.

Hail is a good reflector of energy and will return very high dBZ values. These values are estimates of the rainfall per hour, updated each volume scan, with rainfall accumulated over time. Depending on the type of weather occurring and the area of the U.S., forecasters use a set of rainrates which are associated to the dBZ values. The higher the dBZ, the stronger the rainrate. Typically, light rain is occurring when the dBZ value reaches 20. The scale of dBZ values is also related to the intensity of rainfall. The dBZ values increase as the strength of the signal returned to the radar increases. So, a more convenient number for calculations and comparison, a decibel (or logarithmic) scale (dBZ), is used. Reflectivity (designated by the letter Z) covers a wide range of signals (from very weak to very strong).

“Reflectivity” is the amount of transmitted power returned to the radar receiver. The colors are the different echo intensities (reflectivity) measured in dBZ (decibels of Z) during each elevation scan. Download RadarNow! for Android on Google Play

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