Date: 201204
Local time of day: 1201-1800
Location: ZZZ.ARTCC, US
Flight conditions: IMC
Weather elements / visibility: Turbulence; Cloudy
Light: Daylight
Aircraft: B737-700
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Cruise
Airspace: Class A ZZZ
ATC / advisory: Center ZZZ
Reporter organization: Air Carrier
Reporter function: Pilot Flying; Captain
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Workload; Training / Qualification; Situational Awareness; Human-Machine Interface; Distraction; Confusion; Physiological - Other
Second reporter function: First Officer; Pilot Not Flying
Anomaly: Deviation - Altitude Excursion From Assigned Altitude; Deviation / Discrepancy - Procedural Clearance; Inflight Event / Encounter Weather / Turbulence
Detector: Person Flight Crew
When detected: In-flight
Result: Flight Crew Became Reoriented; General Maintenance Action
Contributing factors: Weather
Primary problem: Weather

Narrative: The purpose of this report is to describe a turbulence encounter which initially produced a momentary MMO exceedence (less than .84 Mach); followed almost immediately by a rapid decrease in airspeed (to stick shaker activation) and subsequent altitude deviation of minus 300 FT from cleared flight level. I was the Captain and pilot flying; cruising at FL370 overhead a Southwestern City at the time of the turbulence encounter. My First Officer (pilot not flying) was busy running the radar and communicating with Center in an effort to avoid the widespread buildups along our route. With the passengers and flight attendants seated; we were deviating around the last ridge of buildups (in and out of IMC) when we observed a towering cumulus directly in our path that didn't appear on radar. As we entered the cloud; we encountered moderate turbulence resulting in an instantaneous MMO exceedence of several seconds. I immediately disengaged both the autopilot and autothrottles; and retarded thrust levers to idle. As we came out of clacker; I advanced the thrust levers steadily as the engines slowly re-spooled; and it appeared for a few moments that our airspeed was stabilizing. However; a few seconds later we experienced a rapid airspeed decrease accompanied by stick shaker; and I responded by advancing the thrust levers to emergency thrust and lowering the nose to keep the airspeed within the yellow maneuvering margin. By this time; we had descended to 36;700 FT; at which point my First Officer advised ATC of our turbulence encounter and altitude deviation. The entire event was of short duration from onset to recovery. Dispatch was notified via ACARS of the MMO exceedence and RVSM airspace deviation. Follow-up with the flight attendants revealed no injuries to passengers or crew. Upon landing and not receiving an ACARS exceedence message; I made an Info Only write-up appropriate for this level of MMO exceedence and notified both Dispatch and Maintenance Control. We over-relied on the radar in this case and underestimated the severity of turbulence associated with cloud tops that were not producing radar returns.


Second narrative: [Narrative #2 contained no additional information]


Synopsis: A B737-700 encountered moderate turbulence in a cloud top which resulted in an MMO exceedence followed by rapid airspeed decrease and a 300 FT altitude loss in order to maintain airspeed.