DEPARTING MEM IN HVY RAIN; HIGH WINDS AND TSTMS; A300 FLT CREW STARTS TKOF ROLL ON TXWY M VICE RWY 36L AS CLRED.

Narrative

TAXIING FOR TKOF FROM MEMPHIS WHILE A HURRICANE WAS PASSING THROUGH DUE E OF THE FIELD. WX CONDITIONS WERE DEFINITELY A FACTOR WITH HVY BLOWING RAIN; POOR VISIBILITY; GUSTY WINDS; WET RWY; WINDSHEAR ALERTS; AND WIPERS ON FULL. WE TAXIED SBOUND ON TXWY N FOR TKOF ON RWY 36L. WE WERE FIRST IN LINE; SO APCHING M1 ON TXWY N; THE TWR CLRED US FOR TKOF; WITH A L TURN TO 310 DEGS AND THEY ALSO GAVE US A WIND DIRECTION; SPD AND GUSTS. I THINK THE WIND WAS 330 DEGS AT 35 KTS GUSTING TO 41 KTS. ON THE RADAR; THERE WERE HVY CELLS 3-4 MI N OFF THE DEP END OF THE RWY. BOTH THE CAPT AND I WERE TRYING TO LOOK AT THE RADAR TO CONFIRM THAT 310 DEGS WOULD BE A SAFE DEP HDG; AS HE TAXIED ONTO THE RWY. AS WE TURNED ONTO M1; THE CAPT CALLED FOR THE 'BELOW THE LINE' PORTION OF THE TKOF CHKLIST. I RESET THE FCP FOR THE 310 DEG HDG; AND DESELECTED THE 'HDG' MODE. WE COMPLETED THE 'BELOW THE LINE' CHKLIST DOWN TO 'LIGHTS;' AND SIMULTANEOUSLY REVIEWED THE WINDSHEAR TKOF PROFILE. THE CAPT TOLD ME TO SELECT 'HDG' AT 400 FT AGL. WE AGAIN LOOKED AT THE RADAR; AND DECIDED THAT THE 310 DEG HDG ASSIGNED WOULD BE SAFE. THE CAPT BEGAN TO ADVANCE THE THROTTLES TO 40% AS I TURNED ON THE LIGHTS; AND ANNOUNCED 'BEFORE TKOF CHKLIST COMPLETE.' AS THE LIGHTS CAME ON; THE CAPT REALIZED WE WERE NOT ON RWY 36L; BUT ON TXWY M; AND SIMULTANEOUSLY PULLED THE THROTTLES TO IDLE AS THE TWR ALSO INFORMED US OF OUR MISTAKE AND CANCELED OUR TKOF CLRNC. UP UNTIL THIS TIME; MY SCAN HAD BEEN INSIDE; COMPLETING THE CHKLISTS; CHKING THE RADAR; REVIEWING THE WINDSHEAR PROFILE; AND MAKING SURE THE ACFT WAS SAFE TO FLY. I WAS ALSO MENTALLY THINKING ABOUT THE WINDS; TO MAKE SURE WE WERE WITHIN LIMITS. BECAUSE OF ALL THAT WAS GOING ON INSIDE THE COCKPIT; I DID NOT LOOK OUTSIDE THE ACFT UNTIL THE CAPT BEGAN HIS REJECTED TKOF; AND THE TWR CANCELED OUR CLRNC. I FEEL LIKE I LET THE CAPT DOWN; BY NOT MAKING SURE WE SAFELY TAXIED ONTO THE RWY. WHEN THE THROTTLES CAME BACK; WE HAD BARELY STARTED TO ROLL; AND CLRED EASILY AT M3. TWR RE-CLRED US FOR TKOF; AND WE REPEATED THE 'BELOW THE LINE' CHKLIST. THE SUBSEQUENT TKOF AND FLT WAS UNEVENTFUL. I WOULD HAVE NEVER BELIEVED THIS COULD HAPPEN TO ME. I STILL CAN'T BELIEVE WE MADE SUCH AN INCREDIBLE MISTAKE. I LEARNED A VALUABLE LESSON THAT MORNING; AND I HOPE SOMEONE ELSE CAN LEARN FROM OUR MISTAKE.