  Using the inverse spectral theory of the nonlinear Schrodinger (NLS) equation
we correlate the development of rogue waves in oceanic sea states characterized
by the JONSWAP spectrum with the proximity to homoclinic solutions of the NLS
equation. We find in numerical simulations of the NLS equation that rogue waves
develop for JONSWAP initial data that is ``near'' NLS homoclinic data, while
rogue waves do not occur for JONSWAP data that is ``far'' from NLS homoclinic
data. We show the nonlinear spectral decomposition provides a simple criterium
for predicting the occurrence and strength of rogue waves (PACS: 92.10.Hm,
47.20.Ky, 47.35+i).
