The primary modes of Pacific Sea Surface Temperature (SST) variability
for all months, 1950-1993, are extracted with Rotated Principal Component Analysis (RPCA), yielding, as the first three modes, the El Nino-Southern Oscillation (ENSO), ENSO-like interdecadal variability, and North Pacific variability. The annual cycle for each mode is constructed by regressing SST for each month of the year against the time series of each mode. Each mode is seen to possess a significant annual cycle, with some features that are completely unresolved in the respective Rotated Principal Components. Notably, the North Pacific variability is seen to be associated with a significant tropical signal, out of phase with the North Pacific maximum during winter and in phase during fall, averaging to zero in the annual mean. The annual cycle of the three modes are compared to the annual cycle evolution of the various climatological features that have been hypothesized to be related; e.g., the North Pacific frontal zones. The long term NCEP reanalysis is used to generate regressions of for various atmospheric quantities, such as wind and diabatic heating, that are associated with the three SST modes