Turbulence intensity and reporting
Turbulence intensities (TC AIM MET Table 15.1): LIGHT, MODERATE, SEVERE, EXTREME.
- Grade by aircraft reaction, not by how it feels.
- No trace level; trace is icing only (TC AIM MET 2.4, Table 2.3).
| Intensity | Code | Aircraft reaction | Inside the cabin |
|---|---|---|---|
| Light | LGT |
Momentary, slight, erratic altitude/attitude, pitch, roll, or yaw changes (report "light turbulence"). Or slight, rapid, rhythmic bumpiness, no appreciable altitude/attitude change (report "light chop"). | Slight strain against belts. Unsecured objects shift slightly. Walking little affected. |
| Moderate | MOD |
Like light but stronger: altitude/attitude changes, airspeed usually varies, but aircraft stays in positive control at all times ("moderate turbulence"). Or rapid bumps/jolts, no appreciable altitude/attitude change ("moderate chop"). | Definite strain against belts. Objects dislodged. Food service and walking difficult. |
| Severe | SEV |
Large, abrupt altitude/attitude changes. Large airspeed variations. Aircraft may be momentarily out of control. | Occupants forced violently against belts. Objects tossed about. Food service and walking impossible. |
| Extreme | XTRM |
Aircraft tossed violently about, practically impossible to control. May cause structural damage. | (FAA AWH 19.1; absent from TC AIM table.) |
- CAR 101.01(1) defines "light turbulence" as in table.
- LGT, MOD, SEV precede a hazard code:
MOD TURB,SEV ICE,SEV MTW.
Frequency (how often, separate from intensity):
| Term | Share of time |
|---|---|
| Occasional | Under 1/3 |
| Intermittent | 1/3 to 2/3 |
| Continuous | Over 2/3 |
Reporting:
- Turbulence PIREP: location(s), time (UTC), intensity, in or near cloud, altitude, aircraft type, duration if applicable.
- CAT reported as CAT, preceded by intensity or chop type (TC AIM MET 2.2.2).
- Pilot encountering CAT: urgently report time, location, flight level, intensity to facility being worked (TC AIM MET 2.2.1).
Trap: grading turbulence by how it feels in the cabin.
References
- FAA Aviation Weather Handbook (FAA-H-8083-28) 19.1
- TC AIM MET 2.2
- TC AIM MET 2.2.2
- TC AIM MET Table 15.1
- CAR 101.01(1)