When using the ARPA in heavy rain, which action should you take?

When navigating using an ARPA (Automatic Radar Plotting Aid) in heavy rain, it is essential to consider the impact of precipitation on radar performance. The effective range of the radar can indeed be reduced in heavy rain conditions due to attenuation of the radar signal as it passes through raindrops. This can lead to a decreased ability to detect targets far away or the loss of weak echoes that would normally be seen in clearer conditions.

Taking into account this reduced effectiveness means that mariners should navigate with heightened caution, adjusting their expectations about the visibility of other vessels or obstacles on the radar screen. It is important to understand that the detection range may not be the same under heavy rain as it is in clear conditions. Thus, planning navigational decisions and maneuvers must account for this limitation, and treating the radar data with an understanding of reduced effective range ensures safer navigation.