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Weather Operations (Cont.)
6.4 WEATHER MAPPING AND INTERPRETATION
This section contains general information on use of the radar for weather
interpretation. Review of this information will assist the pilot.
6.5 OBSERVING WEATHER
A weather radar is only as good as the operator's interpretation of the
echoes that are displayed on the radar indicator. The pilot must combine his
knowledge of how radar works and its limitations with such things as the
prevailing weather pattern, the geographic location, and his personal expe-
rience in order to make a sound interpretation of the displayed targets.
As a starting point, the operator should read FAA Advisory Circular number
00-24B, Subject: Thunderstorms. It is also highly recommended that the
operator take advantage of one of the commercially available weather radar
seminars.
Figure 6.5-1. Storm Components
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RDR-1600 Pilot's Guide
6.5.1 Thunderstorms and Turbulence
The RDR-1600 weather radar can give you a clue to the presence of
turbulence. Areas of the display where the colors change rapidly over a
short distance represent steep rainfall gradients, which are usually associ-
ated with severe turbulence.
Turbulence may be divided into two basic types:
(1) clear-air turbulence. It is not possible to detect clear-air turbulence
(2) turbulence associated with thunderstorms and precipitation. This
Weather guidance is now available from ground radar stations in some
areas. However, this system suffers in comparison with the airborne
weather radar when the weather is clearly visible on the pilot's indicator,
instantly available for the pilot to act upon, considering his immediate
circumstances and future flight planning.
The strong up and down drafts in a thunderstorm create very large rain-
drops which are usually displayed on a radar as level three.
The probability of turbulence in these strong vertical gusts is great. The
National Severe Storms Laboratory (NSSL) has found that the intensity
level of the precipitation reflection correlates with the degree of turbulence
found in a thunderstorm. The most severe turbulence in the storm,
however, may not be at the same place that gives the greatest radar reflec-
tivity.
The rate of change in rainfall rate laterally within a storm is called the rain
gradient. This change will appear on the indicator as a change from green
to yellow to red. If the rainfall rate increases from level one to three in a
short distance, the rain gradient is steep and severe turbulence is often
present. Avoid any storm with a steep rain gradient by an extra margin and
especially avoid flying near the portion of the storm with the steepest
gradient.
TM106101(8/01)
TM106101(8/01)
with this type of radar.
type is most common. Weather radar is most helpful to the pilot
with this type.
RDR-1600 Pilot's Guide
Weather Operations (Cont.)
21
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