A330
Flight Crew Multiengine; Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument
Situational Awareness
Deviation - Altitude Excursion From Assigned Altitude; Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural Clearance; Inflight Event / Encounter Wake Vortex Encounter
Air Traffic Control Issued Advisory / Alert; Flight Crew Returned To Clearance; Flight Crew Took Evasive Action
Environment - Non Weather Related; Human Factors
[We were] 23 miles and 2000 feet below and behind [a] B747.  We were slop 2 miles right when wind shift put us in moderate turbulence.  It was getting worse and required immediate action.  [We] descended 300 ft and slid to the other side of his jet wash. Immediately then returned to assigned altitude and told ATC about the minor deviation.  Tracks too tight. [I used] Captain authority and knowledge.
Altitude deviation due to wake turbulence from preceding aircraft B747. I was Pilot Monitoring.  Captain was Pilot Flying.  We were experiencing moderate turbulence from preceding aircraft.  The Captain removed the offset to get back on course and avoid turbulence since the wind was blowing the wake from the B747 on our path.  Captain selected 36;700 ft. on the FCU and descended 300 ft. to further mitigate the effect of the wake turbulence while getting back on course.  Captain did not check with [ATC] when he initiated a descend to 36;700 ft.; but the time I realized what he was doing; it was too late for me to intervene.  If he would have communicated his intentions I would have had an opportunity to discuss the consequences of an altitude deviation.
A330 flight crew reported they encountered wake turbulence from a preceding B747 while flying a North Atlantic track.  Captain descended 300 feet without clearance to avoid the wake.