Instrument Flying: Technique in Weather Page: 34
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RESTRICTED
T. O. No. 30-100D-1-...-.-- ....
.. r ^uN 4 '1 4---- 300
I
Structure of a squall in
summer: The rain squall
should be circumnavigated
if possible. If necessary,
flight should be conducted
through the cloud mass in
the rain area or above the
ice-crystal level. The in-
termediate level should be
avoided to eliminate the
hazard of ice and lightning.- -~ - A
of the cloud and the level at which ice crystals begin
to form rapidly (-100C). Most precipitation is pro-
duced at or above this level, hence a heavy shower
will develop in and fall from a smaller cloud when
the ice-crystal level is low. If the cloud cannot go
above this level, no precipitation, or only a light
shower of large raindrops, may result.
DANGERS TO EXPECT AND AVOID
Icing conditions will prevail in the upper regions
of all squalls and most showers. The temperature
gage or upper air temperature observations will tell
the pilot the altitude of the freezing level, below which
icing will not occur.
The intensity of the storm is determined mainly by
the rate of decrease of temperature with altitude, and
this same condition determines the vertical velocity
of ascending air. The degree of turbulence may be an-
ticipated with reasonable accuracy by determining thelapse rate before the flight. Since the lapse rate in
a squall is steeper (decreases more rapidly) than in a
shower, turbulence is most severe in a squall. Simi-
larly, since the size of individual cloud droplets and
the quantity of water suspended in a cloud is deter-
mined by the velocity of the ascending air, the rate of
ice formation will be determined by the steepness
of the lapse rate. Therefore, ice accretion is usually
more severe in squalls than in showers.
KNOW THEIR LIFE HISTORIES
A squall or shower has a definite life, history. It
grows, reaches maturity, becomes old and weak, and
finally dies. The intensity of turbulence and icing
conditions is directly related to this cycle. The age
factor must always be considered. A pilot who has
formed his ideas of the intensity of hazards in squalls
from experience with old or decadent storms may get
a dangerous or even disastrous surprise when he
meets a squall at the peak of its maturity.RESTRICTED
Section 6
.4
0
- ~m.
1
34
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Army Air Forces. Instrument Flying: Technique in Weather, book, January 1, 1944; Ashland, Ohio. (https://texashistory.unt.edu/ark:/67531/metapth873973/m1/40/?rotate=270: accessed July 16, 2024), University of North Texas Libraries, The Portal to Texas History, https://texashistory.unt.edu; crediting National WASP WWII Museum.