Narrative:

We were cruising at FL370 a few mi west of liberal VOR, ks. We were in clouds with the seatbelt sign on. The radar showed an echo 80 mi south of our course, 20 mi long and 5 mi wide just north of ama. No other echoes were showing on the radar. I saw clear skies for a few seconds on the right side of the aircraft and at the same time I saw a large buildup directly in front of us. As I was pointing this out to the captain, we flew into the tops of the clouds where we encountered severe turbulence and small hail. We had up- and downdrafts that caused us to lose 500 ft of altitude and we had airspeed fluctuations of up to mach .84 (275 KTS) and down to 225 KTS. Normal cruise speed was mach .78. We exited the clouds 45-60 seconds later into clear skies and smooth air. We notified center of our altitude deviation and flight conditions prior to and during the event. The only area of WX that showed on radar was south of us and we were on the upwind side of the WX. Past experience has showed that this was the best place for us to be. We had no warning prior to the event with other aircraft in the area reporting turbulence no greater than light. After we regained our altitude, I called back to see if the flight attendants were ok. We found out that 2 of our flight attendants were standing in the aft galley when the event occurred. One of them suffered a broken ankle. After we called medlink and dispatch, we elected to divert. No one else was injured and the rest of the flight was uneventful. I can't think of anything that we could have done differently that would have prevented this from happening. Supplemental information from acn 619491: we asked ATC for a deviation to the right of course and got it. We broke out into the clear after about 45-60 seconds. We advised ATC of our severe turbulence encounter and told them that we had seen nothing on radar and they agreed that they had seen nothing on their radar. During the encounter we also experienced either heavy rain or small hail. ATC started vectoring other aircraft away from the area. While we were looking up radio frequencys for dispatch, the 'a' flight attendant contacted us and told us that another flight attendant was injured and that they were looking for medical personnel on board. 2 nurses were on board and assisted while he talked to the doctor on medlink. The doctor decided we should continue on to our destination. We were about to call dispatch again when they called us. The dispatcher and I decided to divert to the nearest suitable airport because of the flight attendant injury. The closest airport was about 95-100 mi to the east of our position. I wrote up the aircraft for the encounter with severe turbulence. After company maintenance inspected the aircraft, and a replacement flight attendant was found, we continued on.

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Original NASA ASRS Text

Title: B737-700 FLT CREW ENCOUNTERS SEVERE TURB AT FL370 NEAR LBL VOR. FLT ATTENDANT INJURIES RESULT IN DIVERSION.

Narrative: WE WERE CRUISING AT FL370 A FEW MI W OF LIBERAL VOR, KS. WE WERE IN CLOUDS WITH THE SEATBELT SIGN ON. THE RADAR SHOWED AN ECHO 80 MI S OF OUR COURSE, 20 MI LONG AND 5 MI WIDE JUST N OF AMA. NO OTHER ECHOES WERE SHOWING ON THE RADAR. I SAW CLR SKIES FOR A FEW SECONDS ON THE R SIDE OF THE ACFT AND AT THE SAME TIME I SAW A LARGE BUILDUP DIRECTLY IN FRONT OF US. AS I WAS POINTING THIS OUT TO THE CAPT, WE FLEW INTO THE TOPS OF THE CLOUDS WHERE WE ENCOUNTERED SEVERE TURB AND SMALL HAIL. WE HAD UP- AND DOWNDRAFTS THAT CAUSED US TO LOSE 500 FT OF ALT AND WE HAD AIRSPD FLUCTUATIONS OF UP TO MACH .84 (275 KTS) AND DOWN TO 225 KTS. NORMAL CRUISE SPD WAS MACH .78. WE EXITED THE CLOUDS 45-60 SECONDS LATER INTO CLR SKIES AND SMOOTH AIR. WE NOTIFIED CTR OF OUR ALTDEV AND FLT CONDITIONS PRIOR TO AND DURING THE EVENT. THE ONLY AREA OF WX THAT SHOWED ON RADAR WAS S OF US AND WE WERE ON THE UPWIND SIDE OF THE WX. PAST EXPERIENCE HAS SHOWED THAT THIS WAS THE BEST PLACE FOR US TO BE. WE HAD NO WARNING PRIOR TO THE EVENT WITH OTHER ACFT IN THE AREA RPTING TURB NO GREATER THAN LIGHT. AFTER WE REGAINED OUR ALT, I CALLED BACK TO SEE IF THE FLT ATTENDANTS WERE OK. WE FOUND OUT THAT 2 OF OUR FLT ATTENDANTS WERE STANDING IN THE AFT GALLEY WHEN THE EVENT OCCURRED. ONE OF THEM SUFFERED A BROKEN ANKLE. AFTER WE CALLED MEDLINK AND DISPATCH, WE ELECTED TO DIVERT. NO ONE ELSE WAS INJURED AND THE REST OF THE FLT WAS UNEVENTFUL. I CAN'T THINK OF ANYTHING THAT WE COULD HAVE DONE DIFFERENTLY THAT WOULD HAVE PREVENTED THIS FROM HAPPENING. SUPPLEMENTAL INFO FROM ACN 619491: WE ASKED ATC FOR A DEV TO THE R OF COURSE AND GOT IT. WE BROKE OUT INTO THE CLR AFTER ABOUT 45-60 SECONDS. WE ADVISED ATC OF OUR SEVERE TURB ENCOUNTER AND TOLD THEM THAT WE HAD SEEN NOTHING ON RADAR AND THEY AGREED THAT THEY HAD SEEN NOTHING ON THEIR RADAR. DURING THE ENCOUNTER WE ALSO EXPERIENCED EITHER HVY RAIN OR SMALL HAIL. ATC STARTED VECTORING OTHER ACFT AWAY FROM THE AREA. WHILE WE WERE LOOKING UP RADIO FREQS FOR DISPATCH, THE 'A' FLT ATTENDANT CONTACTED US AND TOLD US THAT ANOTHER FLT ATTENDANT WAS INJURED AND THAT THEY WERE LOOKING FOR MEDICAL PERSONNEL ON BOARD. 2 NURSES WERE ON BOARD AND ASSISTED WHILE HE TALKED TO THE DOCTOR ON MEDLINK. THE DOCTOR DECIDED WE SHOULD CONTINUE ON TO OUR DEST. WE WERE ABOUT TO CALL DISPATCH AGAIN WHEN THEY CALLED US. THE DISPATCHER AND I DECIDED TO DIVERT TO THE NEAREST SUITABLE ARPT BECAUSE OF THE FLT ATTENDANT INJURY. THE CLOSEST ARPT WAS ABOUT 95-100 MI TO THE E OF OUR POS. I WROTE UP THE ACFT FOR THE ENCOUNTER WITH SEVERE TURB. AFTER COMPANY MAINT INSPECTED THE ACFT, AND A REPLACEMENT FLT ATTENDANT WAS FOUND, WE CONTINUED ON.

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.