AN MD80 FLT CREW CROSSES THE HOLD SHORT LINE FOR RWY 36L AT TPA; FL.

Narrative

WHILE TAXIING FOR TKOF ON TPA RWY 36L; I WAS CONCERNED ABOUT A TSTM WHICH HAD JUST PASSED OVER THE FIELD AND WAS NOW N OF THE ARPT. THE FIELD WAS VERY WET WITH STANDING WATER FROM THE RECENT SHOWER; AND I ATTEMPTED TO POS THE ACFT WHILE IN THE HOLDING PAD SO THAT THE RADAR WOULD BE ABLE TO PAINT OUR DEP RTE AS I HELD SHORT OF THE RWY. I PASSED WHAT I THOUGHT WAS A CAT III HOLD LINE APCHING THE RWY; BUT AS I CAME TO A STOP NEARER THE RWY; THERE WAS NO OTHER HOLD SHORT LINE. AT NO TIME DID WE INTRUDE ON THE ACTUAL RWY OR PASS ANY RWY EDGE LIGHTS OR RWY EDGE MARKINGS; BUT IT IS POSSIBLE WE WERE BEYOND THE HOLD SHORT LINE. TWR MADE NO MENTION OF OUR POS; AND WHEN CLRED FOR TKOF; WE TAXIED ONTO THE RWY AND DEPARTED NORMALLY. IF THE HOLD SHORT LINE I BELIEVED WAS A CAT III HOLD LINE WAS IN FACT THE NORMAL HOLD SHORT LINE; IT APPEARED TO BE FARTHER FROM THE RWY THAN I WAS EXPECTING; BUT THE WET TXWYS AND DARKNESS AT THE END OF THE RWY MADE IT DIFFICULT TO SEE IN ANY CASE. SUPPLEMENTAL INFO FROM ACN 620831: THE CAPT LATER TOLD ME THAT DUE TO THE LACK OF VISUAL CLUES HE MISTOOK A SEAM IN THE CONCRETE TO BE THE HOLD SHORT LINE. I ALSO FAILED TO NOTICE BECAUSE OF HEADS DOWN DUTIES PRIOR TO TKOF.