ACFT EQUIP OPERATING PROC REGARDING TCASII ON DEP TFC SIT. MULTIPLE RWY OP PARALLEL RWYS.

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WE RECEIVED A TA WHILE TAKING OFF ON RWY 27L AT PHL. THE RA WAS INHIBITED DUE TO LOW ALT. TWR DID NOT ADVISE US OF A JETSTREAM THAT APPARENTLY HAD DEPARTED RWY 27R; WHICH IS DISPLACED ABOUT 4500 FT E OF RWY 27L. STRONG N WINDS APPARENTLY BLEW THE JETSTREAM CLOSER TO RWY 27L AND IF WE HAD DELAYED OR FORGOTTEN THE 255 DEG HDG OFF OF RWY 27L WE COULD HAVE EASILY FLOWN/CLBED INTO THE HIGHER ACFT. WE INITIALLY DID NOT SEE THE TA ON THE TCASII BECAUSE WE HAD IT IN THE WX PLUS TCASII MODE. THIS PUT THE CONFLICT AT THE VERY BOTTOM OF THE SCREEN WHICH IS PARTIALLY BLOCKED BY THE VERT SPD CARDS. THE FO HAD IT IN THIS MODE DUE TO HABITS OF OPERATING A DIFFERENT SETUP WHICH IS ALSO ON SOME OF OUR ACFT. I DID NOT CONSIDER IT THAT CRITICAL; HOWEVER; IN THE FUTURE I WILL HAVE IT ONLY IN THE TCASII MODE IF WX IS NOT NEEDED. THIS PLACES YOUR ACFT IN THE CTR OF THE SCREEN AND DISPLAYS ACFT THAT ARE ABEAM AND AFT OF YOUR POS. THE TWR SHOULD HAVE ADVISED US OF AN ACFT THAT HAD TAKEN OFF BEHIND US -- THEY USUALLY DO.