Operational Definitions of Turbulence Categories

Category

Measures

Horizontal

Vertical

Light

·        Rhythmic bumpiness without appreciable changes in altitude and/or attitude,

·        Momentary, slight, erratic changes in  altitude and/or attitude,

·        No loss of control,

3 - 5 knots per 1000 feet

Moderate

·        Rapid bumps or jolts without appreciable changes in altitude and/or  attitude

·        Momentary, erratic changes in altitude and/or attitude and variation in airspeed attitude

·        No loss of control

24 - 49 knots per 90 nautical miles

6 - 9 knots per 1000 feet

Severe

·        Large, abrupt changes in altitude and/or attitude,

·        Momentary loss of control

50 - 89 knots per 90 nautical miles

10 - 15 knots per 1000 feet

Extreme

·        Violent tossing,

·        Loss of control,

·        Possible damage

> 90 knots per 90 nautical miles

> 15 knots per 1000 feet