Global Express (BD700)
Flight Crew Multiengine; Flight Crew Instrument; Flight Crew Air Transport Pilot (ATP)
Workload; Time Pressure
Deviation - Altitude Overshoot; Deviation - Altitude Excursion From Assigned Altitude; Inflight Event / Encounter Loss Of Aircraft Control; Inflight Event / Encounter Weather / Turbulence
Flight Crew Took Evasive Action; Flight Crew Regained Aircraft Control
Weather
While in cruise flight and VMC conditions we encountered an unforecast high-altitude thunderstorm where we apparently rode right through the tops of. Our aircraft radar did not paint this activity and ATC did not show this on their radar either. The aircraft was pushed up approximately 400-800 feet; the auto-pilot disengaged; auto-throttles disengaged; aircraft indications showed an over-speed condition; stall indication; massive wind noise; and turbulence as the aircraft passed through the system.The flight crew became aware of the severe weather when the aircraft went from being in a smooth; stable flight in clear skies to being rapidly pushed up. In addition to the incredible wind noise and several notices from the aircraft such as the auto-throttles being disengaged; the auto-pilot being disengaged; the notice of 'stall;' and the airspeed going into the red on the speed tape. These conditions such as STALL and the airspeed going into the red were instantaneous and lasted less than a couple of seconds.Unforecast high-altitude thunderstorm where we apparently rode right through the tops. Our aircraft radar did not paint this activity and ATC did not show this on their radar either. In addition; we were operating in VMC conditions with clear skies.The Pilot Flying immediately maneuvered the aircraft.  The evasive maneuver was very brief before returning on course and to the assigned altitude. Shortly after this; we requested a block altitude of FL430-450; as we began a cruise climb to our assigned oceanic altitude. Upon completion of the flight; a very thorough post-flight inspection was completed.
Global Express Captain reported a brief period of loss of aircraft control due to  an unforecasted high altitude severe weather encounter.