Summary: Neutrino \((\nu)\) oscillations during the core collapse and bounce of a supernova (SN) are shown to generate the most powerful detectable gravitational wave (GW) bursts. The SN neutronization phase produces mainly electron \((\nu_e)\) neutrinos, the oscillations of which must take place within a few mean-free paths of their resonance surface located near their neutrinosphere. Here we characterize the GW signals produced by spin-flip oscillations inside the fast-rotating protoneutron star in the SN core. In this novel mechanism, the release of both the oscillation-produced \(\nu_\mu\)’s, \(\nu_\tau\)’s and the spin-flip-driven GW pulse provides a unique emission offset \(\Delta T_{\text{GW}\leftrightarrow\nu}^{\text{emission}}=0\) for measuring the \(\nu\) travel time to Earth. As massive \(\nu\)’s get noticeably delayed on its journey to Earth with respect to the GW, they generate over the oscillation transient, the accurate measurement of this time-of-flight delay by SNEWS + LIGO, VIRGO, BBO, DECIGO, etc. can assess the absolute \(\nu\) mass spectrum straightforwardly.