Narrative:

My first officer was flying the leg from msy to jax. We were on an easterly heading, in the clouds, and level at FL330. We unexpectedly encountered moderate turbulence that was generated by a cell which 'popped up' on our WX radar. I directed my first officer to turn right toward smoother air. While he was turning I noticed that we began to gain altitude. I directed him to 'push over' to correct, but due to the strong updraft and the upward vector, we 'topped out' at approximately 33700 ft or 33600 ft. My first officer had failed to notice that the turbulence had caused the altitude hold function of our autoplt to disengage. As a result, he entered this unintentional climb. Once back down to FL330, we re-engaged the altitude hold function and the remainder of the flight was uneventful. The elapsed time from start to finish of his deviation was about 15 seconds (maybe less). There was not a conflict with other traffic, there was not any traffic on our TCASII, and ZJX did not comment about the deviation. As we returned to level flight, I immediately reported the moderate turbulence to ZJX.

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Original NASA ASRS Text

Title: AN ACR MLG EXPERIENCES AN ALTDEV WHEN THEIR ALT HOLD ON THE AUTOPLT KICKS OFF WHILE DEVIATING FROM TSTMS AND TURB.

Narrative: MY FO WAS FLYING THE LEG FROM MSY TO JAX. WE WERE ON AN EASTERLY HEADING, IN THE CLOUDS, AND LEVEL AT FL330. WE UNEXPECTEDLY ENCOUNTERED MODERATE TURB THAT WAS GENERATED BY A CELL WHICH 'POPPED UP' ON OUR WX RADAR. I DIRECTED MY FO TO TURN R TOWARD SMOOTHER AIR. WHILE HE WAS TURNING I NOTICED THAT WE BEGAN TO GAIN ALT. I DIRECTED HIM TO 'PUSH OVER' TO CORRECT, BUT DUE TO THE STRONG UPDRAFT AND THE UPWARD VECTOR, WE 'TOPPED OUT' AT APPROX 33700 FT OR 33600 FT. MY FO HAD FAILED TO NOTICE THAT THE TURB HAD CAUSED THE ALT HOLD FUNCTION OF OUR AUTOPLT TO DISENGAGE. AS A RESULT, HE ENTERED THIS UNINTENTIONAL CLB. ONCE BACK DOWN TO FL330, WE RE-ENGAGED THE ALT HOLD FUNCTION AND THE REMAINDER OF THE FLT WAS UNEVENTFUL. THE ELAPSED TIME FROM START TO FINISH OF HIS DEV WAS ABOUT 15 SECONDS (MAYBE LESS). THERE WAS NOT A CONFLICT WITH OTHER TFC, THERE WAS NOT ANY TFC ON OUR TCASII, AND ZJX DID NOT COMMENT ABOUT THE DEV. AS WE RETURNED TO LEVEL FLT, I IMMEDIATELY RPTED THE MODERATE TURB TO ZJX.

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.