Overtalk, you are drawing some very sensible conclusions regarding to that weather phenonoma described in post 316. All of a sudden you find yourself outside your envelope with consequently odd indications in terms of speed which might have led to the stream of ACARS messages. Though, we simply don't know yet.
I've heard a few similar stories of pilots crossing the ITCZ and encountering such a "pool of warm air" with the associated turbulence.
For them it was only a matter of time when they came out of the pool unharmed due their relative low weight at that time.
Marsipulami.