MEM CTLR; ATTEMPTING TO RELIEVE SUPVR ON POSITION; WITNESSED OPERROR AT APPROX 3000; WHEN ISSUED INSTRUCTIONS FAILED TO ENSURE SEPARATION.

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MY SUPVR ASSIGNED ME TO GET HIM/HER OUT OF E AND W PARALLEL FINALS POS COMBINED; SO I PLUGGED IN TO GET A BRIEFING. HE/SHE WAS WORKING 2 ACFT; A P180 AND AN FA20; AND BOTH ACFT WERE GENERALLY EBOUND AT 3000 FT FOR RWY 27 (BOTH ACFT WERE IN E ARRS AIRSPACE). THERE WERE NUMEROUS TSTMS IN THE AREA; AND THE WIND HAD JUST SHIFTED FROM 190 DEGS AT 10-12 KTS TO 340 DEGS AT 25 KTS WITH GUSTS TO 43 KTS. ADDING TO THE COMPLEXITY WAS THE FACT THAT WE DIDN'T HAVE ENOUGH STAFFING TO COORDINATE WITH THE TWR FOR A RWY CHANGE. THE P180 WAS ASSIGNED A 090 DEG HDG AND THEY WERE ABOUT 4 MI N OF THE RWY 27 LOC. THE SUPVR ASSIGNED THE FA20 THE SAME HDG TO PROVIDE A SIMILAR DOWNWIND; BUT THE FA20 ASKED FOR 20 DEGS R FOR WX; WHICH THE SUPVR APPROVED; ADDING AN ASSIGNED 090 DEG HDG WHEN ABLE. HE THEN ASSIGNED THE P180 A 180 DEG HDG AND A DSCNT TO 2000 FT. THE FA20 RPTED ON A 090 DEG HDG ABOUT 1 1/2 OR 2 MI N OF THE RWY 27 LOC. THE SUPVR INSTRUCTED THE FA20 TO A 060 DEG HDG TO WIDEN HIM OUT. AS I WAS ABOUT TO MENTION THAT THAT HDG MIGHT NOT BE ENOUGH; ANOTHER CTLR IN THE ROOM YELLED; 'HEY; WATCH THOSE TWO.' THE SUPVR INSTRUCTED THE P180 TO USE NO DELAY IN THE DSCNT TO 2000 FT AND THEN TURNED THE P180 TO A 240 DEG HDG AND GAVE THE ILS RWY 27 CLRNC. THE P180 AND THE FA20 APPEARED TO PASS ABOUT 2 TO 2 1/2 MI ABEAM EACH OTHER WITH 400-600 FT VERT SEPARATION. AT THIS POINT; SINCE THE BRIEFING HAD NOT EVEN BEGUN; THE SUPVR INSTRUCTED ME TO TAKE CARE OF THE COORD NEEDED WITH THE TWR TO MAKE A RWY CHANGE. WHEN I HAD ACCOMPLISHED THAT; THE SUPVR HAD CLOSED THE POS HE HAD BEEN WORKING; AND IT WAS THEN THAT I RPTED THE ALLEGED ERROR TO HIM. THE FAA RPT LISTED THE OFFICIAL SEPARATION AS 2.71 MI AND 500 FT.