MLG HITS HVY RAIN ON LNDG ROLL HAS RWY EXCURSION.

Narrative

DURING TROPICAL STORM GORDON; SHOT AN IFR APCH TO RWY 9L AT FLL. VISIBILITY RPTED TO BE 1 MI WITH WINDS AT APCH END 170 DEG AT 12 KTS AND 140 DEGS AT 28 KTS AT E END OF FIELD. BROKE OUT ON APCH AT 400 FT AGL; 150 FT ABOVE MINIMUMS; TO GOOD VIEW OF RWY AND LNDG AREA. 30 DEG FLAPS AND AUTOBRAKES AT HVY BRAKING POS. IT WAS RAINING BUT WITH WIPERS ON; VISIBILITY WAS GOOD. AFTER TOUCHDOWN AND REVERSE THRUST WAS APPLIED; HIT WALL OF HVY RAIN THAT DISTORTED VISUAL PICTURE AND HAMPERED ABILITY TO MAINTAIN DIRECTIONAL CTL. ACFT DRIFTED TO R (WXVANED) AND HIT RWY SIDE LIGHT. AS I CORRECTED TO L; WE BROKE OUT OF HVY RAIN AND MADE A NORMAL STOP. UPON GATE INSPECTION; NOTICED 1 TIRE ON R MAIN WAS CUT. NO FURTHER PROBS. MY RADAR WAS SHOWING A CELL AT THE END OF THE RWY MOVING SE TO NW. THE RAIN WE ENCOUNTERED WAS NOT DEPICTED. I WOULD NOT HAVE EVEN STARTED THE APCH IF I COULD HAVE BEEN INFORMED THAT THE 'RAIN' WAS IN FACT 'HEAVY RAIN.' FEEDBACK FROM THE TWR AND FROM OTHER ACFT; ONE WHO HAD JUST MISSED IN FRONT OF US; WOULD HAVE BEEN QUITE HELPFUL IN DECIDING TO GO OR NOT TO GO.