B737-500 LNDG SFO ENCOUNTERS WING VORTICES ON SHORT FINAL INTO SFO.

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INITIAL CLRED FOR RNAV RWY 28R APCH. FIELD CONDITIONS RPTED; CALM WINDS; 10 SM VISIBILITY; SKC; TEMP 14 DEGS C; ALTIMETER 29.99 INCHES. FLT WAS ASKED TO SWITCH TO VISUAL RWY 28L. ANOTHER ACR B737 WAS COMING 'DOWN THE BAY' FROM THE GOLDEN GATE ARR CORRIDOR. WE WOULD NOW FOLLOW AN MD80 7 MI AHEAD FOR RWY 28L. WE VISUALLY ACQUIRED BOTH ACFT AND IMMEDIATELY OFFSET FOR THE L RWY TO ALLOW TURNING ROOM FOR THE ACR B737 THAT WOULD GO 'BELLY UP' TO US; WHILE MAKING HIS R HAND 180 DEG TURN TO LINE UP FOR RWY 28R. AS WE APCHED THE 'BRIJJ' WE NOTED WINDS 020 DEGS/20 KTS; AN 80 DEG R TO L XWIND. THE ACR B737 WAS NOW APPROX 4000 FT AHEAD AND TO THE R OF US; SLIGHTLY HIGHER AND FULLY CONFIGURED. WE CROSSED BRIJJ FULLY CONFIGURED; (GEAR DOWN; 3000 FT) ON SPD; (APPROX 130 KTS) AND ON GS. AT APPROX 1300 FT AGL; BOTH MY FO AND I; VISUALLY ACQUIRED A FUNNEL SHAPED VORTICES EMERGING FROM THE VICINITY OF THE OTHER B737; HEADED TOWARDS OUR ACFT FROM R 1-2 O'CLOCK POS. IT WAS HORIZLY ORIENTED; ABOUT 3 FT IN WIDTH AT THE WIDE FORWARD END AND TIGHTLY WOVEN. THIS 'TORNADO' SHAPED VORTICES; RESEMBLED A CLR; GLASS-LIKE FUNNEL; RAPIDLY APCHING OUR ACFT. THE VORTEX INITIALLY CAUSED A R ROLLING MOMENT; CORRECTED BY L AILERON AND A SMALL AMOUNT OF L RUDDER; THE SECOND TURB LIKE UNCOMMANDED ROLL; WAS MORE VIOLENT CAUSING A L ROLLING MOMENT. THIS REQUIRED NEARLY FULL R AILERON; AND A LARGE R RUDDER INPUT TO LEVEL THE ACFT. I ANTICIPATED THIS SUBSEQUENT ROLL AND ALSO ADDED THRUST. WE ROLLED OUT L OF RWY 28L CTRLINE AND APPROX 146 KTS WITH THE ADDED PWR. I HAD MY FO MAKE A BRIEF ANNOUNCEMENT TO THE PAX AND ATC. WE RE-ESTABLISHED OURSELVES ON RWY 28L AND FLEW A STABILIZED APCH TO AN UNEVENTFUL LNDG. SUPPLEMENTAL INFO FROM ACN 451502: THE ENTIRE EVOLUTION FROM ONSET TO SIGHTING TO FINAL RECOVERY LASTED BTWN 25-30 SECONDS. AFTER RE-STABILIZING AT APPROX 1000 FT FLT XXX PROCEEDED TO AN UNEVENTFUL LNDG AT SFO STAYING SLIGHTLY ABOVE THE GLIDE PATH OF THE PRECEDING ACFT.