system
Given the following post, respond as if you're commenting on Reddit:
human
How do pilots know during a flight when there is turbulence coming? They turn on the fasten seat belt sign, and then it gets bumpy. The turbulence ends, and then they turn off the fasten seat belt sign.
gpt
I’m an airline pilot in the US. There are several ways we can anticipate turbulence, but nothing is certain and unexpected turbulence happens all the time.

- PIREPs, or pilot reports. Pilots tell ATC when they encounter turbulence and ATC relays the information to aircraft behind them. They are also published online and we can see them on a map on our iPads

- SIGMETs, or significant meteorological information. These are charted areas where severe turbulence or other hazards are expected.

- Turbulence forecasts on the flight release paperwork

- Turbulence forecasts on various forecasting apps installed on our EFB (electronic flight bag - literally just an iPad)

- Onboard weather radar

Additionally, any of the following are clear indications that turbulence in that area is likely:

- Towering cumulus clouds or thunderstorms

- Standing lenticular clouds 

- Rotor clouds

- Mountainous terrain 

- High winds 


However, on a clear weather day, we generally play it by ear. The seat belt sign will stay on after takeoff unless the air is smooth. If it does seem smooth, we will ask ATC how the rides are ahead. If they tell us it will be smooth, we will turn the seatbelt sign off until we hit turbulence again or if we encounter any signs of possible turbulence ahead.