A driver in front of you is signaling with his or her hand and arm pointing upward. This driver wants to

You may use your vehicle's signal lights or hand signals. If the signal lights are not working or if bright sunlight makes them hard to see, use hand signals. A driver in front of you who signals with his or her hand and arm pointing upward is about to turn right. [Signaling; Safe Driving Practices; California Driver Handbook]