B737-800
Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument; Flight Crew Multiengine
Flight Crew Last 90 Days 400
Inflight Event / Encounter Wake Vortex Encounter; Inflight Event / Encounter Weather / Turbulence
General None Reported / Taken
Environment - Non Weather Related; Procedure
While cruising at FL360 between JORDY way point and KP72C way point; on our flight to ZZZ; the aircraft suddenly and unexpectedly encountered a pocket of moderate turbulence lasting for less than five seconds. Up until that point; the flight had been completely smooth as Air Traffic Control and our weather packet indicated. The only possible explanation was that we must have hit the wake turbulence of an extremely heavy crossing traffic; however; we didn't see any visually; or on the TCAS. Even though the seatbelt sign was off; the Flight Attendants indicated that there were no passengers standing at the time. The rest of the flight was smooth again all the way to ZZZ. I think that the only way to prevent this type of event from happening is for Air Traffic Control to be more wary and informative about the potential for wake turbulence to exist in the vicinity of heavy or super-type aircraft. And possibly more studies need to be done to see what the persistence of this type of turbulence is.
B737-800 Captain reported encountering wake turbulence at FL360; apparently from an unreported heavy aircraft.