B777-200
Flight Crew Air Transport Pilot (ATP)
Fatigue; Distraction
Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter Weather / Turbulence
Flight Crew Became Reoriented; Flight Crew Returned To Clearance
Weather; Human Factors
To avoid weather I SLOPPED 2 miles left of track.  Once clear of the weather I neglected to return to a Strategic Lateral Offset Procedure (SLOP) right of track.  My Relief First Officer (RFO) noticed the error and we corrected back to a right of track SLOP.   This occurred on a random route across the Pacific for a period of approximately 45 minutes.This was my error.  I thought a momentary deviation to the left of course to avoid weather would not be a problem.  But then I forgot due to distraction with weather and turbulence and maybe a little fatigue. Rather than Execute an offset just use heading select to momentary get around a build up.  Pay more attention to detail.
A B777 Captain reports using the FMC to deviate left of track two miles for weather then forgetting to return to a right offset for the oceanic crossing.