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PRIMUS
r
880
Digital
W
eather
Radar
System
A28-1146-102-00
Radar Facts
5-40
Shadowing
An operating technique similar to the REACT blue field is shadowing. To
use the shadowing technique, tilt the antenna down until ground is being
painted just in front of the storm cell(s). An area of no ground returns
behind the storm cell has the appearance of a shadow behind the cell.
This shadow area indicates that the storm cell has totally attenuated the
radar energy and the radar cannot show any additional targets (WX or
ground) behind the cell. The cell that produces a radar shadow is a very
strong and dangerous cell. It should be avoided by 20 miles.
WARNING
DO NOT FLY INTO THE SHADOW BEHIND THE CELL.
Turbulence Probability
The graph of turbulence probability is shown in figure 5-29. This graph
shows the following:
D There is a 100% probability of light turbulence occurring in any area
of rain.
D A level one storm (all green) has virtually no chance of containing
severe or extreme turbulence but has between a 5% and 20%
chance that moderate turbulence exists.
D A level two storm (one containing green and yellow returns) has
virtually no probability of extreme turbulence but has a 20% to 40%
chance of moderate turbulence and up to a 5% chance of severe
turbulence.
D A level three storm (green, yellow, and red radar returns) has a 40%
to 85% chance of moderate turbulence, a 5% to 10% chance of
severe turbulence, and a slight chance of extreme turbulence.
D A level four storm (one with a magenta return) has moderate
turbulence, a 10% to 50% chance of severe turbulence, and a slight
to 25% chance of extreme turbulence.
WARNING
THE AREAS OF TURBULENCE MAY NOT BE ASSOCIATED WITH
THE MAXIMUM RAINFALL AREAS. THE PROBABILITIES OF
TURBULENCE ARE STATED FOR THE ENTIRE STORM AREA,
NOT JUST THE HEAVY RAINFALL AREAS.