B767 CAPT USED HIS EMER AUTH TO AVOID RPTED SEVERE TURB.

Narrative

WE WERE PROCEEDING WITH AN OCEANIC XING AT FL310; TRACK 'ECHO.' I WAS THE PF. THE CAPT AND I WERE IN THE COCKPIT; THE OTHER FO WAS ON HIS REST BREAK. WE BEGAN TO ENCOUNTER VARYING DEGREES OF TURB. SEVERAL ACFT WERE GIVING RPTS ON TURB. ONE RPT WAS FROM AN ACFT ROUTED ALONG OUR TRACK (E) AT FL330. HE PRECEDED US BY APPROX 4-6 DEGS OF LONGITUDE. HE RPTED ENCOUNTERING 'SEVERE TURB' AND SOME DEGREE OF 'LOSS OF CTL.' OUR TURB INCREASED TO 'MODERATE TURB;' AND IF THERE COULD BE DIFFERENT LEVELS OF 'MODERATE;' I WOULD CALL IT 'HVY' MODERATE. DURING THIS TIME (BEGINNING WHEN WE FIRST EXPERIENCED SOME TURB) THE CAPT AND I DISCUSSED OUR OPTIONS CONCERNING CABIN NOTIFICATION; ACFT SPD; ENG IGNITION AND POSSIBLE AVOIDANCE ACTIONS. BASED ON OUR CURRENT TURB LEVEL; WX RPTS; PIREPS; ETC; THE CAPT WANTED TO DSND. I EXPRESSED MY DISAGREEMENT WITH THAT ACTION. PASSING 38 DEGS W LONGITUDE THE CAPT ASSUMED CTL OF THE ACFT; AND WITH INCREASING CONCERN FOR THE POSSIBLE SEVERE TURB IN FRONT OF US; BEGAN A DSCNT. I AGAIN EXPRESSED MY DISAGREEMENT WITH THE DECISION TO DSND; AND WANTED TO OFFSET OUR RTE IF WE CONTINUED. HE NOTED MY OBJECTIONS AND CONTINUED DOWN ALONG THE RTE. AT THIS POINT I CONTACTED GANDER RADIO TO GET A CLRNC FOR FL290. WE HAD REACHED FL290; THE RIDE WAS SMOOTHER (LIGHT CHOP ONLY) AND I EXPRESSED MY DESIRE TO CLB BACK TO OUR FILED AND CLRED ALT. GANDER RADIO RESPONDED TO OUR REQUEST; BUT WAS UNABLE TO APPROVE FL290; AND THE CAPT BEGAN A CLB BACK TO FL310. WE WERE LEVEL AGAIN AT FL310 JUST PASSING 39 DEGS W LONGITUDE. THE TURB WE ENCOUNTERED EARLIER WAS NOT PRESENT AND THE REMAINDER OF THE FLT WAS UNEVENTFUL. SHORTLY THEREAFTER I WAS RELIEVED BY THE OTHER FO AND BEGAN MY REST BREAK WHICH LASTED UNTIL APPROX 35 MINS BEFORE LNDG. THERE WAS LITTLE DISCUSSION OF THE EVENT; BUT I INFORMED THE CAPT OF MY INTENTION TO FILE THIS RPT.