React (Hazard Display Feature) - Honeywell IntuVue RDR-4000 Pilot's Manual

IntuVue RDR-4000 Weather Radar Pilot's Guide

REACT (Hazard Display Feature)

REACT stands for Rain Echo Attenuation Compensation Technique. As
the transmitted radar signal travels through heavy rain it loses power, or
becomes attenuated. If this attenuation is severe enough, weather
behind a storm cell may not be detectable, or it may be displayed as
being less severe than it actually is (e.g., green instead of yellow).
The Hazard Display Configuration of the RDR-4000 automatically
indicates areas where the radar signal has been attenuated. These
areas are shown as magenta arcs superimposed over the reflectivity in
the areas where the signal attenuation is significant. These arcs
indicate that there could be severe weather in that area, even though
only mild or no reflectivity is shown.
In areas where the REACT field is shown, expect the possibility of
weather that may need to be avoided. The geometry between the
aircraft and the attenuating weather may change as the flight
progresses. This may allow weather that was in the REACT area to
later be outside of the REACT field, and the radar will then more clearly
display weather in that area.
Expanded Operating Instructions D201002000008
16 Rev 1, December 2014