Narrative:

After departure from mci vector heading approximately 260 degrees to parallel line of thunderstorms along front in northern kansas, we were at FL310 with autoplt engaged. Cleared by ATC to deviate as necessary and attempt to find a hole in line of WX to turn north. A break between 2 thunderstorms appeared and we turned north to cross the line of WX. Just prior to entering the area between storms there seemed to be a phenomena like strong wave action and moderate turbulence that lasted only briefly but caused the aircraft to climb 400-500 ft. At that time the autoplt disconnected by itself and the first officer manually took control of the aircraft and descended back to FL310. Shortly thereafter we were cleared to FL330. To the best of my knowledge there was no traffic conflict.

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Original NASA ASRS Text

Title: DC9 ACFT IN CRUISE AND BEING VECTORED AND DEVIATING FOR WX ENCOUNTERED WX RELATED WAVE ACTION RESULTING IN UPDRAFT AND ACFT CLBING ABOVE ASSIGNED ALT.

Narrative: AFTER DEP FROM MCI VECTOR HEADING APPROX 260 DEGS TO PARALLEL LINE OF TSTMS ALONG FRONT IN NORTHERN KANSAS, WE WERE AT FL310 WITH AUTOPLT ENGAGED. CLRED BY ATC TO DEVIATE AS NECESSARY AND ATTEMPT TO FIND A HOLE IN LINE OF WX TO TURN N. A BREAK BTWN 2 TSTMS APPEARED AND WE TURNED N TO CROSS THE LINE OF WX. JUST PRIOR TO ENTERING THE AREA BTWN STORMS THERE SEEMED TO BE A PHENOMENA LIKE STRONG WAVE ACTION AND MODERATE TURB THAT LASTED ONLY BRIEFLY BUT CAUSED THE ACFT TO CLB 400-500 FT. AT THAT TIME THE AUTOPLT DISCONNECTED BY ITSELF AND THE FO MANUALLY TOOK CTL OF THE ACFT AND DSNDED BACK TO FL310. SHORTLY THEREAFTER WE WERE CLRED TO FL330. TO THE BEST OF MY KNOWLEDGE THERE WAS NO TFC CONFLICT.

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.