AN MD80 FLT CREW RECEIVES A TCASII RA.

Narrative

CLBING THROUGH APPROX 13000 FT MSL WE RECEIVED A TFC ALERT (TCASII) FOR TFC AT APPROX OUR 11 O'CLOCK POS ABOUT 5 MI AND 800 FT BELOW US. THE TFC WAS SLIGHTLY OUT CLBING US AND CONVERGING. WE THEN RECEIVED AN RA TO REDUCE OUR CLB RATE AND THEN ANOTHER RA TO DSND. AFTER WE BEGAN OUR DSCNT; THE TCASII ADVISED US OF XING TFC. I NOTICED ON THE TCASII HOWEVER THAT IT APPEARED THAT THE CONFLICTING TFC STOPPED THEIR CLB AND ALSO BEGAN A DSCNT. OUR TCASII CONTINUED TO ADVISE A DSCNT. THE TFC WAS CONVERGING ON OUR POS AND WAS WITHIN 100 FT OF OUR ALT. I INCREASED THE RATE OF DSCNT WHICH REACHED AT LEAST 4000 FT A MIN AT ONE POINT. WHEN WE WERE ADVISED CLR OF CONFLICT WE LEVELED AT 11000 FT MSL AND THEN RESUMED OUR CLB. WE ADVISED ATC OF OUR TCASII MANEUVER. THEY WERE OBVIOUSLY UNAWARE OF ANY TFC NEARBY (OR AT LEAST DIDN'T ACKNOWLEDGE IT TO US). A VERY ROUGH ESTIMATE OF THE CLOSEST PROX OF THE TFC WAS 1 MI HORIZLY AND 0 FT VERTLY. WE NEVER DID ACQUIRE A VISUAL ON THE TFC TO ASCERTAIN TYPE; DIRECTION OF TRAVEL; ETC.