WHILE ON VECTOR TO OAK RWY 11; AN MD80 FLC INITIATES A GPWS ESCAPE MANEUVER DUE TO ACFT GPWS ALARM. PIC CONCERNED WITH VECTORS TOWARDS MOUNTAINOUS TERRAIN.

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LOCATION: 25 NM E; JUST W OF THE SCAGGS ISLAND (SGD) VOR. WHILE IN THE WX; ACFT 1 BEING VECTORED FOR AN ILS APCH TO RWY 11 AT OAK ARPT; BAY APCH ASKED US TO DSND TO 4000 FT FROM 6000 FT. A DISCUSSION ABOUT THE MSA ENSUED. I NOTICED THE RADIO ALTIMETER RISING ABOUT 3 TIMES THE RATE THE PRESSURE ALTIMETER WAS MOVING AT. AS WE LEVELED AT 4000 FT; THE TERRAIN WARNING SOUNDED AND I EXECUTED THE PRESCRIBED ESCAPE MANEUVER -- WITH A SUBSEQUENT CLB TO 6700 FT. THE FO COMMUNICATED TO ATC THAT WE WERE DOING THE ESCAPE. SOME CONFUSION ENSUED IN THIS COM BTWN THE CTLR AND THE FO. THE CTLR ASKED WHAT ALT WE INTENDED TO LEVEL OFF AT. THE FO TOLD HIM 6000 FT. AT THAT POINT; WE WERE IN THE ESCAPE CLBING THROUGH 6400 FT; WITH A SUBSEQUENT LEVELOFF AT 6700 FT; FOLLOWED BY AN IMMEDIATE DSCNT TO 6000 FT. THERE WAS TFC IN THE AREA THAT WE ACQUIRED ON TCASII AND VISUALLY (ACFT #2). WHEN I WAS SATISFIED THE TERRAIN EVENT HAD ENDED; WE WERE ABOVE THE CLOUDS. THE FLT THEN PROCEEDED UNEVENTFULLY TO OAK. I BELIEVE THE CTLR LOST SEPARATION BTWN MY ACFT AND THE GND. THE NEXT FLT SCHEDULED WAS CANCELED DUE TO A POSSIBLE ENG OVERTEMP. SUPPLEMENTAL INFO FROM ACN 425870: RPTR HAD CONCERNS WHEN ATC DSNDED HIS ACFT FROM 6000 FT TO 4000 FT; KNOWING HE COULD BE IN THE VICINITY OF MOUNT DIABLO. THE RPTR ADVISED THAT HE HAD BEEN VECTORED OFF THE SGD 107 DEG RADIAL; AND JUST PRIOR TO THE GPWS ALERT; APCH CTL TURNED HIM TO A 270 DEG HDG. HE STATED THAT WHILE ON VECTORS; APCH CTL FORGOT ABOUT HIM; THUS THE 270 DEG TURN. WHEN HE SAW THE QUICKLY RISING RA INDICATIONS; HE SAID HE WAS READY FOR THE ESCAPE MANEUVER CLB. THE PIC COMMANDED THE FO TO ADVISE APCH CTL THAT THEY WOULD LEVEL AT 6000 FT. HE ADMITS THAT THIS MAY HAVE CAUSED SOME CONFUSION WITH THE CTLR BECAUSE HE WAS CLBING THROUGH 6200 FT; REACHING 6700 FT PRIOR TO DSNDING BACK TO 6000 FT. THE RPTR STATED HE IS FREQUENTLY TURNED IN TOO TIGHT TO THE FINAL WHEN APCHING FROM THE N; HAVING TO MAKE A 'PRETTY RAPID DSCNT TO TRY AND CATCH THE GS.' THE RPTR ADVISED HE WOULD RATHER BE VECTORED OUT FURTHER; AT ANY TIME; 'IN ORDER TO SET UP A MUCH MORE STABILIZED APCH.' ANALYST AND RPTR DISCUSSED OTHER COMPLEXITIES INVOLVED WITH ACFT SEQUENCING TO SFO AND OAK ARPTS.