IRFP-01
Metro Review
(a) Vertical limits of the highest winds are usually 3,000 to
4,000 ft above and below the jet stream core
b. Satellite photos can give strong clues as to the jet stream
locations
NOTE: Although there are few clouds at the jet stream core
level, there is often considerable cloudiness below. These
clouds are long and strung out along the jet stream.
F. Clear air turbulence (CAT) 21.1.1.4.1.1
Fig 13: Jet Stream
Clear Air Turbulence
1. Types
(CAT)
a. Jet stream CAT
(1) CAT external to jet stream
(a) Especially severe when jet stream interacts with large
mountain range or deep low-pressure system
(b) Can be anticipated when curving jet stream occurs on
polar side of deep low-pressure system--greatest
turbulence found on low-pressure side of jet stream
and when wind speed exceeds 110 kts
(c) Can be anticipated along the jet stream north and
northeast of a rapidly deepening low-pressure system
(d) Occurs frequently on inside of curve where jet stream
Fig 14: Areas of
turns sharply
Probable CAT in Jet
Stream
(2) CAT internal to jet stream
(a) Can be found most often in areas of rapidly changing
wind speeds
(b) Common near areas of highest wind velocity within jet
stream, on polar side and below core
NOTE: Remember that the jet stream moves north in
summer and south in winter.
b. Mountain wave CAT
Fig 15: Mountain
Wave Clear Air
(1) High velocity airflow over mountain range is disrupted and
Turbulence (CAT)
causes turbulence over and downwind of range
(2) Produces large “waves” of air with strong updrafts and
downdrafts
(3) Can extend to 5,000 ft above tropopause and to 300 miles
or more downwind of range
(8-97) Original
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