IntuVueRDR-7000 Weather Radar Pilot's Guide
D201911000094 Principles of Weather Radar Use
Rev 0, Feb 2020 45
SECTION 5: PRINCIPLES OF WEATHER RADAR USE
WEATHER RADAR PRINCIPLES
Airborne weather avoidance radar, as its name implies, is for avoiding
severe weather - not for penetrating it. Whether to fly into an area of
radar echoes depends on echo intensity, spacing between the
echoes, and the capabilities of both pilot and aircraft. Remember that
weather radar detects only precipitation; it does not detect minute
cloud droplets. Therefore, the radar display provides no assurance of
avoiding inclement weather in clouds and fog. Your display may be
clear between intense echoes; this clear area does not necessarily
mean you can fly between the storms and maintain visual separation
from them.
Weather radar detects droplets of precipitation size. The strength of
the radar return (echo) depends on drop size, composition, and
amount of water. Water particles return almost five times as much
signal as ice particles of the same size. This means that rain is more
easily detected than snow, although at times large, wet snowflakes
may give a strong return.
Hail usually has a film of water on the surface; consequently, a
hailstone is often reflected as a very large water particle. Because of
this film and because
hailstones usually are larger
than raindrops,
thunderstorms with large
amounts of wet hail return
stronger signals than those
with rain. Although wet hail is
an excellent reflector of
radar energy, some hail
shafts are extremely small
(100 yards or less) and make
poor radar targets. If
hailstones are cold and dry,
they give poor returns and
might not show on the
display.
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