Metro-01
Review of Basic Meteorological Principles
b. Hail
(1) Can occur in any thunderstorm at all altitudes
(2) Can occur beneath or up to 20 miles in front of the anvil
top of large thunderstorms--denoted by a distinct shade of
blue
(a) Under the anvil is particularly hazardous
(b) Can be found anywhere around the storm (in clear air)
(3) Can cause severe structural damage
NOTE: The largest recorded hail stone was 17 inches in
circumference and weighed 1.5 lbs.
c.
Tornadoes
(1) Occur most often with steady-state thunderstorms
associated with cold fronts or squall lines
(2) Very intense local phenomena with windshears clocked at
more than 26,000 fpm (260 kts)
(3) Can be embedded in thunderstorm and thus invisible to
pilot
(4) Mostly a low-level phenomenon, does not penetrate the
storm more than 1,000 to 2,000 ft up into the bottom of the
clouds
NOTE: "Waterspouts" are tornadoes that occur over
bodies of water.
d. Lightning
(1) Can cause temporary or permanent loss of vision
(2) Can puncture aircraft skin
(3) Can damage electronic equipment and compass
(4) Probability of strikes to aircraft
(a) Probability is highest near the tops of thunderstorms
(near the anvil region), decreasing rapidly with altitude
(b) Highly electrified clouds can be advected many miles
from the parent storm
NOTE: Avoid any clouds downwind of thunderstorms.
(7-97)
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