Certainly on a 737 high and low speed buffet are distinguishable as Bergerie1 says, but I would hesitate to guarantee that identification in a CB!
All this talk of descent rate and 'impact at 0215' - we do not know, do we? Until the FDR and CVR are (hopefully) read, we can 'surmise', but we don't know when impact occurred. If for any reason ACARS had stopped transmitting they could have been flying for a while!