ACR HAS TCASII RA; CLBS.

Narrative

20 NM E OF MEM AT FL280 OUR ACFT TCASII INITIATED A CLB COMMAND DUE TO CONFLICTING TFC. COMMAND REQUIRED AN IMMEDIATE CLB RATE OF 2000 FPM. TFC (IN RED) WAS OPPOSITE DIRECTION AND SHOWING A -2.5 BELOW. WE CLBED THROUGH FL289 BEFORE OUR TCASII COMMANDED 'MONITOR VERT SPD' AND EVENTUALLY THE CONFLICTING ACFT WAS WELL BEHIND US WHEN THE RA TERMINATED. IMMEDIATE NOTIFICATION WAS MADE TO MEMPHIS CTR HOWEVER WE WERE ALREADY AT 900 FT ABOVE OUR ASSIGNED ALT BEFORE THEY ACKNOWLEDGED OUR CALL (TCASII WAS STILL SHOWING A -2.5 DIFFERENCE AT FL289). WE RETURNED TO FL280 AND REQUESTED INFO ABOUT THE ACFT. IT WAS AN LGT A TYPE ACFT TRAVELING OPPOSITE DIRECTION. THEY HAD JUST RECEIVED A CLB FROM FL250 TO FL260. IT WAS APPARENTLY DURING THEIR CLB WHEN OUR TCASII INTERPRETED THE ACFT AS A POTENTIAL MID AIR AND THUS ISSUED A RA. WE RADIOED LGT A BUT THEY DID NOT ADMIT TO ANYTHING UNUSUAL IN THEIR CLB OR CRUISE NOR WERE THEY TCASII EQUIPPED. MEMPHIS CTR ALSO STATED THEIR EQUIP DID NOT SHOW AN ALT EXCURSION BY LGT A. ONE CURIOUS ASPECT WAS THAT THE -2.5 ALT DIFFERENTIAL WITH THE ACFT NEVER CHANGED EVEN WITH THE 1000 FT CLB THAT WE INITIATED.