Will my flight be bumpy?
Type where you are flying from and to, and the day. You get an estimate of how bumpy the air may be on your route, in plain words, with a picture of where along the way it is likelier. Free, no sign-up, your trip stays on your device.
What this is. A rough estimate worked out from public weather model data. It is not a safety statement, not a flight forecast from your airline, and not medical advice or treatment for fear of flying. If flying causes you real distress, a doctor or a psychologist can help.
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An estimate from one public weather model run, ranked against other routes in the same run. It has not yet been checked against pilot reports.
lowlightbumpy patchesnoticeable
Why bumps happen, and why the plane is built for them
- It is moving air, not a hole. Wind at cruising height changes from place to place, especially near jet streams. An aircraft crossing the edge between faster and slower air gets pushed up and down. It is like a boat crossing waves.
- Aircraft are built for far more than you will feel. Wings are tested during certification by bending them well beyond the loads of any normal flight. The wing is made to flex, and that flex soaks up much of the bump.
- The seat belt sign is routine, not an alarm. Crews switch it on so that no one is standing when the cabin moves. Keep your seat belt fastened while seated.
- Pilots plan around it. They get weather briefings, other aircraft report what they find, and they can ask air traffic control for a different height.
- Bumps feel bigger than they are. From the seat, a drop of a few metres can feel much larger than it is.
How the estimate is made
NOAA's Global Forecast System (GFS) publishes winds and heights at several pressure levels. Every few hours a script reads the 300, 250 and 200 hPa levels (around 9 to 12 km up, where airliners cruise), and works out Ellrod's TI1 index: the vertical wind shear between 300 and 200 hPa multiplied by the horizontal stretching and shearing of the wind at 250 hPa. Ellrod and Knapp described it in 1992 as a way to flag clear-air turbulence from model winds (Weather and Forecasting, 7(1), 150 to 165). We average it over one-degree squares and read it along the straight great-circle path between your airports, using the forecast hour that matches the time you would be at each point.
The limits, plainly. It is a model-based index, not a measured bump forecast, and we have not yet checked it against pilot reports. Real routes bend around weather, the model is coarse, and small patches can be missed or invented. The four bands are ours and relative: they split the world's values for one model run (the top quarter, tenth and twentieth of values), so "low" does not mean "nothing". Do not use this for flight planning. For your own flight, trust the crew.
Weather data from the US National Oceanic and Atmospheric Administration (NOAA) GFS, public domain. This page is not made, checked or endorsed by NOAA. Positions of airports are rounded.
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