Narrative:

Descending on the arrival to be over zzzzz intersection at 11;000/250 knots. Reached 11;000 feet early and slowed to 250 for turbulence penetration. There was a small line of low cumulus clouds (approximately tops 14;000 no weather radar returns) running from the northeast to the southwest just west of the VOR. Prior to entering the clouds we notified passengers and flight attendants of possible rough ride ahead. After entering the clouds we encountered light to occasional moderate turbulence. We then experienced approximately 30 seconds to one minute of moderate to severe turbulence which automatically disengaged the autopilot; airspeed fluctuations of +/- 25 to 30 knots and the aircraft began an uncontrollable climb to 12;700 feet. The turbulence ended upon leaving the clouds and we manually returned to 11;000 feet/250 knots prior to zzzzz intersection; our descent clearance restriction and reestablished all automation. Clouds were not unusual other than their linear make-up and low tops for any established line and weather radar did not depict turbulence or rain activity. We notified ATC as well as maintenance control to ensure the g-limits were not exceeded. The automatic autopilot disconnect occurred in normal speed ranges and no aircraft speed exceedance occurred (220 knots to 275 knots at 11;000 feet). All passengers and flight attendants were strapped in no apparent aircraft damage or reported injuries. All bins remained closed and cabin items secured. As a precaution the aircraft was written up for a maintenance inspection. We had no indication until encounter of severe turbulence. Clouds looked to be rough meaning light to moderate and normally penetrated; we never expected or anticipated the turbulence that would automatically climb the airplane 1700 feet after autopilot disengagement with no control response from the side stick. The elevator was going up and we were along for the ride. We fly through these type clouds everyday in our operation and we had no indication of the severity of the bumps and the reaction of the aircraft until we they were encountered. Once again I want to stress we had no radar returns and the tops of these clouds were below 15;000 feet OAT +16. The only slightly unusual aspect was the linear line up from the northeast to the southwest.

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Original NASA ASRS Text

Title: A319 Captain reports encountering moderate to severe turbulence upon entering a low cumulus cloud with no radar returns. The autopilot disengages and the aircraft climbs 1;700 feet with the reporter applying nose down control stick input.

Narrative: Descending on the arrival to be over ZZZZZ Intersection at 11;000/250 knots. Reached 11;000 feet early and slowed to 250 for turbulence penetration. There was a small line of low cumulus clouds (approximately tops 14;000 no weather radar returns) running from the northeast to the southwest just west of the VOR. Prior to entering the clouds we notified passengers and flight attendants of possible rough ride ahead. After entering the clouds we encountered light to occasional moderate turbulence. We then experienced approximately 30 seconds to one minute of moderate to severe turbulence which automatically disengaged the autopilot; airspeed fluctuations of +/- 25 to 30 knots and the aircraft began an uncontrollable climb to 12;700 feet. The turbulence ended upon leaving the clouds and we manually returned to 11;000 feet/250 knots prior to ZZZZZ Intersection; our descent clearance restriction and reestablished all automation. Clouds were not unusual other than their linear make-up and low tops for any established line and weather radar did not depict turbulence or rain activity. We notified ATC as well as Maintenance Control to ensure the G-limits were not exceeded. The automatic autopilot disconnect occurred in normal speed ranges and no aircraft speed exceedance occurred (220 knots to 275 knots at 11;000 feet). All passengers and flight attendants were strapped in no apparent aircraft damage or reported injuries. All bins remained closed and cabin items secured. As a precaution the aircraft was written up for a maintenance inspection. We had no indication until encounter of severe turbulence. Clouds looked to be rough meaning light to moderate and normally penetrated; we never expected or anticipated the turbulence that would automatically climb the airplane 1700 feet after autopilot disengagement with no control response from the side stick. The Elevator was going up and we were along for the ride. We fly through these type clouds everyday in our operation and we had no indication of the severity of the bumps and the reaction of the aircraft until we they were encountered. Once again I want to stress we had no radar returns and the tops of these clouds were below 15;000 feet OAT +16. The only slightly unusual aspect was the linear line up from the northeast to the southwest.

Data retrieved from NASA's ASRS site as of April 2012 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.