"It was a bit bumpy" tells the crew behind you almost nothing. A turbulence report only helps if everyone means the same thing by each word, so aviation defines the intensities by what the aircraft actually does, and pairs them with how often the bumps come. Learn the scale and your reports become useful, and other pilots' reports become readable.
This is general educational information, not operational, legal, or regulatory advice. Rules differ by authority and change over time. Always verify against current official sources and follow your operator's approved procedures.
Why it is judged by the aircraft, not the feel
The same patch of air feels very different in a light trainer and a heavy jet, so turbulence is graded by the aircraft's reaction and the effect on the occupants rather than by a subjective sense of roughness. That is what makes a pilot report comparable: when a crew calls moderate turbulence, they are describing a defined effect, not a mood.
The intensity scale
The FAA Aeronautical Information Manual sets out four intensities, and SKYbrary summarises them the same way:
- Light: slight, momentary changes in attitude, or a slight, rhythmic bumpiness; occupants feel a slight strain against the seatbelt and unsecured objects stay put.
- Moderate: more pronounced changes in attitude and altitude, but the aircraft stays in control at all times; occupants feel a definite strain against the belt and loose objects move about.
- Severe: large, abrupt changes in attitude and altitude, with the aircraft momentarily out of control; occupants are forced violently against the belt and loose objects are tossed about.
- Extreme: the aircraft is tossed about so violently that it is practically impossible to control and may suffer structural damage.
The FAA also uses chop, light or moderate, for a rhythmic, rapid bumpiness without the larger excursions of altitude. ICAO Annex 3 air-reports use light, moderate and severe.
How often: the frequency words
Intensity is only half the message. The report pairs it with how often the turbulence occurs:
- Occasional: less than one third of the time;
- Intermittent: between one third and two thirds of the time;
- Continuous: more than two thirds of the time.
So "occasional moderate" and "continuous moderate" are the same strength but a very different ride.
A worked example
Cruising at FL080 near a line of building cumulus, you hit bumps that repeatedly throw the aircraft enough to need a firm correction, you feel a definite strain against the belt, and your kneeboard slides off the seat, but you keep full control throughout. The bumps come and go, present perhaps half the time over a five-minute stretch.
That is moderate turbulence (full control retained, but pronounced changes and loose items moving) at an intermittent frequency (a third to two thirds of the time). The report to pass, alongside your position, altitude, time and aircraft type, is "intermittent moderate turbulence, FL080." A controller can relay that to following aircraft and to the air-report system defined in ICAO Doc 4444, and the next crew can decide whether to request a different level.
Common pitfalls
- Do not inflate it. Calling moderate turbulence severe sends others on needless reroutes and dilutes the word when it is genuinely needed.
- Frequency is not intensity. Continuous light is not worse than occasional severe; report both so the meaning is clear.
- Aircraft type matters to the reader. A report from a light aircraft and one from an airliner in the same air may differ, so the type is part of the message.
In Pilot EFB
Pilot EFB keeps the pilot reports and the SIGMETs and AIRMETs you have pulled in one place, so you can see where turbulence has already been reported along your route and brief for it before you set off. A briefing you have already pulled stays readable with no signal; fetching fresh reports needs a connection. Pilot EFB is not a certified Electronic Flight Bag, so treat it as a study and planning aid and brief from your official source of record.