Narrative:

We were at cruise flight 33000 ft and inbound to den. We were cleared directly to tomsn and the tomsn arrival to den, further cleared a descent to 19000 ft. Both crew members, captain and myself verbally verified and pointed to the altitude set in the MCP. We were descending into an area of turbulence due to thunderstorms and numerous cells developing. I proceeded to transfer radio to the captain while I announced the seatbelt sign and spoke on the intercom with the flight attendants regarding a bumpy descent. Upon my return to ATC communications, I heard den and the captain's xmissions regarding our altitude we were descending through. The captain responded 25000 ft and ATC said we were cleared only to 29000 ft and to turn right 30 degrees. The turn was performed and this put us directly into a large cell so the captain turned further right in his climb to avoid the cell. We saw TCASII traffic at 250 approximately 10 mi out and it became a TA call during his pull up and turn. I would estimate the closest was after our turn at 26500 ft and climbing at approximately 9 to 10 O'clock and 3 mi. Our corrective action and the miscom of altitude allowed us to come within 5 mi of the traffic. Possibly we took someone else's clearance to 19000 ft but unfortunately both crew members thought it was for our flight. ATC made a good and timely call to keep an RA from occurring.

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Original NASA ASRS Text

Title: LGT HAS CLRNC CONFUSION AND DSNDS BELOW ALT CTLR EXPECTED.

Narrative: WE WERE AT CRUISE FLT 33000 FT AND INBOUND TO DEN. WE WERE CLRED DIRECTLY TO TOMSN AND THE TOMSN ARR TO DEN, FURTHER CLRED A DSCNT TO 19000 FT. BOTH CREW MEMBERS, CAPT AND MYSELF VERBALLY VERIFIED AND POINTED TO THE ALT SET IN THE MCP. WE WERE DSNDING INTO AN AREA OF TURB DUE TO TSTMS AND NUMEROUS CELLS DEVELOPING. I PROCEEDED TO TRANSFER RADIO TO THE CAPT WHILE I ANNOUNCED THE SEATBELT SIGN AND SPOKE ON THE INTERCOM WITH THE FLT ATTENDANTS REGARDING A BUMPY DSCNT. UPON MY RETURN TO ATC COMS, I HEARD DEN AND THE CAPT'S XMISSIONS REGARDING OUR ALT WE WERE DSNDING THROUGH. THE CAPT RESPONDED 25000 FT AND ATC SAID WE WERE CLRED ONLY TO 29000 FT AND TO TURN R 30 DEGS. THE TURN WAS PERFORMED AND THIS PUT US DIRECTLY INTO A LARGE CELL SO THE CAPT TURNED FURTHER R IN HIS CLB TO AVOID THE CELL. WE SAW TCASII TFC AT 250 APPROX 10 MI OUT AND IT BECAME A TA CALL DURING HIS PULL UP AND TURN. I WOULD ESTIMATE THE CLOSEST WAS AFTER OUR TURN AT 26500 FT AND CLBING AT APPROX 9 TO 10 O'CLOCK AND 3 MI. OUR CORRECTIVE ACTION AND THE MISCOM OF ALT ALLOWED US TO COME WITHIN 5 MI OF THE TFC. POSSIBLY WE TOOK SOMEONE ELSE'S CLRNC TO 19000 FT BUT UNFORTUNATELY BOTH CREW MEMBERS THOUGHT IT WAS FOR OUR FLT. ATC MADE A GOOD AND TIMELY CALL TO KEEP AN RA FROM OCCURRING.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.