• A thunderstorm is one or several
cumulonimbus clouds accompanied by
lightning and thunder.
• Three Ingredients:
– Lifting force
– Unstable Air
– Moist air
• Wind shear
– An abrupt change in wind direction and/or
velocity
• Lightning
• Hail
• Tornados
• Don’t land or takeoff in the face of an approaching thunderstorm.
• Don’t attempt to fly under a thunderstorm.
• Don’t fly without airborne radar into a cloud mass containing
scattered embedded thunderstorms.
• Avoid any thunderstorm by at least 20 miles.
• Clear the top of a known or suspected severe thunderstorm by at
least 1,000 ft altitude for each 10 knots of wind speed at the cloud
top.
• Circumnavigate the entire area if the area has 6/10 thunderstorm
coverage.
• Regard any thunderstorm with top 35,000 feet or higher as
extremely hazardous.
If you cannot avoid penetrating a thunderstorm do the following
before entering the thunderstorm:
• Tighten your safety belt and put your shoulder harness on.
• Plan a hold your course to take you through the storm in a
minimum time.
• To avoid the most critical icing, establish a penetration altitude
below the freezing level or above the level of minus 15 degrees
Celsius.
• Verify/turn on pitot heat, carb heat or jet engine anti-ice.
• Establish power settings for turbulence penetration airspeed (VA).
• Turn up the cockpit lights to highest intensity.
• Disconnect the autopilot.
• If using airborne radar, tilt the antenna up and down occasionally to
detect other thunderstorms.
Follow these guidelines during thunderstorm penetration:
• Keep your eyes on your instruments, this will decrease the danger
of temporary blindness from lightening.
• Don’t change power settings; maintain settings for the
recommended turbulence penetration airspeed.
• Don’t attempt to maintain constant altitude; let the aircraft “ride
the waves.”
• Don’t turn back once your are in the thunderstorm, a straight
course through the storm will most likely get you out of the hazards
most quickly.
• Isolated / Air mass thunderstorms
– Last 20min to 1.5 hours
• Cools the surface below the storm in the mature stage which inhibits updrafts
and cuts off the storms supply of water vapor.
• Frontal / Steady State thunderstorms
– Associated with fronts, converging winds and troughs aloft.
– Sometimes embedded in cloud masses and called embedded
thunderstorms
• Dangerous for all pilots, especially those without radar.
• Squall line thunderstorms
– Most dangerous of all
– Narrow bands of very active thunderstorms that may produce a line
that is too long to detour and wide/severe to penetrate.
– Produces the most intense weather hazards to aircraft
•
•
•
•
Tornadoes
Large hail
Heavy rain
Strong winds
The areas forecast to
have thunderstorms or
severe thunderstorms
are depicted to the
right of the line.
-4
MIA
35