A B737 FLT CREW EXPERIENCES TEMPORARY LOSS OF ACFT CTL WHILE ENCOUNTERING MODERATE TURB NEAR TSTM ACTIVITY AT FL410 ON FREQ WITH ZHU; TX.

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WE WERE CRUISING AT FL410 (FILED ALT). THERE WERE NO BAD RIDE RPTS UP AHEAD; BUT ZHU DID ADVISE US OF AN AREA OF BUILDING TSTMS UP AHEAD AND GAVE US A SLIGHT RERTE TO AVOID THEM. WE COULD SEE THE BUILDING STORMS AHEAD OF US; BUT WE WERE GOING TO BE ABOVE AND TO THE N OF THEM ON OUR RTE OF FLT. PRIOR TO THE EVENT; WE COMPUTED OUR AIRSPD RANGE (.73 - .80). OUR OPTIMUM ALT IN THE FMC WAS FL400. THE CAPT TURNED THE SEATBELT SIGN ON AND ADVISED THE FLT ATTENDANTS TO BE SEATED JUST IN CASE THE RIDE GOT ROUGH. AT WHAT APPEARED TO BE ABOUT 20 NM N OF THE NEAREST STORM; STILL IN CLR AIR; WE ENCOUNTERED MODERATE TURB. I IMMEDIATELY CALLED ATC AND REQUESTED LOWER AND A DEV FURTHER N FOR WX. THE CTLR TOLD US TO DEV AS NECESSARY AND DSND TO FL270. WE IMMEDIATELY STARTED A DSCNT; BUT ABOUT 15 SECONDS LATER; WE SEEMINGLY GOT CAUGHT IN AN UPDRAFT AS WE WERE UNABLE TO CONTINUE DSNDING AND ACTUALLY STARTED CLBING AGAIN. OUR AIRSPD SUBSEQUENTLY BLED OFF TO APPROX .74 MACH AND WE GOT THE STICK SHAKER FOR ABOUT 5 SECONDS; WHICH SURPRISED ME AT THAT AIRSPD. WE WERE THEN ABLE TO CONTINUE THE DSCNT AND THE AIRSPD RAPIDLY INCREASED TO APPROX .82 MACH WHERE WE GOT THE CLACKER. WE SUBSEQUENTLY GOT THE AIRSPD UNDER CTL AND CONTINUED OUR DSCNT TO FL270. THE WHOLE EVENT LASTED 5-10 MINS. I CALLED BACK TO CHK ON THE FLT ATTENDANTS AND PAX AND THEY WERE ALL FINE. I THOUGHT THE CAPT DID AN ABSOLUTELY OUTSTANDING JOB OF CTLING THE ACFT IN THIS SUDDEN UNSUSPECTED VOLATILE SIT. I BELIEVE WE DID EVERYTHING RIGHT AS A CREW. IT IS VERY EASY TO GET SUCKED INTO BELIEVE IF YOU ARE ABOVE A STORM OR OFF TO THE SIDE THAT TURB WILL NOT BE AN ISSUE. ALSO; CRUISING ABOVE OPT ALT (FL400 IN THIS CASE) DOES LIMIT YOUR OPTIONS IF YOU DO ENCOUNTER TURB. WE AGREED THAT PLTS SHOULD STRONGLY CONSIDER IN THE FUTURE TO NOT FLY ABOVE OPTIMUM ALT IF THERE IS A CHANCE TO ENCOUNTER THIS KIND OF TURB; EVEN IF YOU ARE FILED THERE.