Final answer:
When precipitation is moving toward the radar, the base radial velocity is positive, indicating that the precipitation is approaching the radar. Conversely, when precipitation is moving away from the radar, the base radial velocity is negative, indicating that the precipitation is moving away from the radar.
Step-by-step explanation:
The base radial velocity is the component of velocity that is directed straight towards or away from the radar. In the context of precipitation, when precipitation is moving toward the radar, the base radial velocity would be positive. This means that the precipitation is approaching the radar. On the other hand, when precipitation is moving away from the radar, the base radial velocity would be negative. This indicates that the precipitation is moving away from the radar.