Telephonics RT-1601 RT - Tornadoes; Hail

Weather Operations (Cont.)
Weather Operations (Cont.)
22 RDR-1600 Pilot’s Guide TM106101(8/01) TM106101(8/01) RDR-1600 Pilot’s Guide
23
6.5.3Hail
Hail usually has a film of water on its surface; consequently, a hailstone is
often reflected as a very large water particle. Because of the film and
because hail stones 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). These narrow shafts make poor
radar targets.
Hail shafts are usually identified with four different characteristics patterns:
(1) fingers and protrusions, (2) hooks, (3) scalloped edges on the cloud out
-
line and (4) U-shaped cloud edges 3 to 7 miles across.
These echoes appear quite suddenly and along any edge of the storm out
-
line. They also change in intensity and shape in a matter of seconds, and
for this reason careful monitoring of the display is essential. It must be
noted that weak or fuzzy projections are not normally associated with hail;
however, such echoes should be watched closely for signs of rapid intensi
-
fication.
The 40-mile operating range seems best and, with occasional up-tilt to
check for fresh hail from above, generally good results can be obtained.
Note
+It takes an experienced eye to identify “hooks” and “fingers” and
other radar echo characteristics which can indicate hail or torna-
does. However, the pilot can be sure that any echo with very
ragged edges or rapid changes in shape or intensity will contain
severe turbulence.
Figure 6.5.3-1.Finger
Figure 6.5.3-2.Hook
Figure 6.5.3.3.Scalloped
Edge
Figure 6.5.3-4.U-Shaped
6.5.2Tornadoes
It is possible that conclusive methods of detecting tornadoes with airborne
radar may eventually be developed. However, evidence collected to date
indicates tornadoes may be detected if the following echoes are observed:
1. A hook-shaped pendant which may be 5 or more miles long and in the
general shape of the numeral 6 strongly suggests the presence of a
major tornado, especially if the pendant is a bright one and if it projects
from the southwest quadrant (northeast quadrant in the southern hemi-
sphere) of a major thunderstorm moving eastward. The pendant may be
lost in ground clutter when viewed on the indicator and in some cases
might not be much more than a blunt projection or scalloped edge of the
parent thunderstorm echo.
2. A crescent-shaped indentation on the side of a major thunderstorm echo
3 to 7 miles long is another possible identifier of an active or potential
tornado in the vicinity.
3. The best procedure is to make wider than usual detours around sharp-
edged thunderstorms and especially those which show projections or
crescent-shaped indentations.