Narrative:

Flying at altitude we were deviating around areas of isolated thunderstorms. A period occurred that nothing on the radar was appearing except for an area beyond 80 mi. Flying along; the captain noticed an area as he tilted the radar down that needed a deviation immediately. As we were asking ATC; we ended up in it almost within just a few seconds. The best course of action was to fly straight ahead and ride the flight through the thunderstorm top. During the ride we experienced moderate turbulence and a mach exceedance of .86 for less than 7 seconds. Seat belt sign was on and the 3 flight attendants were in the aft galley when event occurred. All 3 flight attendants were injured. No passenger injuries were reported that I am aware of. Flight continued to destination and medical treatment to the 3 flight attendants was administered. Our belief is that this thunderstorm was well below the scan of the radar and was building at a very good rate of 5000-6000 ft per second. By the time it was noticed; we just happened to be on top of it. A potentially better scan of the radar when areas are developing thunderstorms and taking the best course of deviations necessary. In my 23 yrs of flying; I have never had an event like this occur. I hope it never happens again.

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Original NASA ASRS Text

Title: A B737 AT FL410 ENCOUNTERED TURBULENCE ABOVE A RAPIDLY DEVELOPING TRW RESULTING IN THREE FLT ATTENDANT INJURIES AND A MACH AIRSPEED EXCEEDANCE.

Narrative: FLYING AT ALT WE WERE DEVIATING AROUND AREAS OF ISOLATED TSTMS. A PERIOD OCCURRED THAT NOTHING ON THE RADAR WAS APPEARING EXCEPT FOR AN AREA BEYOND 80 MI. FLYING ALONG; THE CAPT NOTICED AN AREA AS HE TILTED THE RADAR DOWN THAT NEEDED A DEV IMMEDIATELY. AS WE WERE ASKING ATC; WE ENDED UP IN IT ALMOST WITHIN JUST A FEW SECONDS. THE BEST COURSE OF ACTION WAS TO FLY STRAIGHT AHEAD AND RIDE THE FLT THROUGH THE TSTM TOP. DURING THE RIDE WE EXPERIENCED MODERATE TURB AND A MACH EXCEEDANCE OF .86 FOR LESS THAN 7 SECONDS. SEAT BELT SIGN WAS ON AND THE 3 FLT ATTENDANTS WERE IN THE AFT GALLEY WHEN EVENT OCCURRED. ALL 3 FLT ATTENDANTS WERE INJURED. NO PAX INJURIES WERE RPTED THAT I AM AWARE OF. FLT CONTINUED TO DEST AND MEDICAL TREATMENT TO THE 3 FLT ATTENDANTS WAS ADMINISTERED. OUR BELIEF IS THAT THIS TSTM WAS WELL BELOW THE SCAN OF THE RADAR AND WAS BUILDING AT A VERY GOOD RATE OF 5000-6000 FT PER SECOND. BY THE TIME IT WAS NOTICED; WE JUST HAPPENED TO BE ON TOP OF IT. A POTENTIALLY BETTER SCAN OF THE RADAR WHEN AREAS ARE DEVELOPING TSTMS AND TAKING THE BEST COURSE OF DEVS NECESSARY. IN MY 23 YRS OF FLYING; I HAVE NEVER HAD AN EVENT LIKE THIS OCCUR. I HOPE IT NEVER HAPPENS AGAIN.

Data retrieved from NASA's ASRS site as of May 2009 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.