The reversal of warming or cooling trends of ENSO cycles occurs most frequently toward the end of calendar
year. We show evidences that prior to the peaks of major warm (cold) episodes, an anomalous anticyclone (cyclone)
over Philippine Sea rapidly establishes. Associated anomalous easterlies (westerlies) prevail in the equatorial western
Pacific which, by forcing oceanic Kelvin waves, provide a negative feedback to the eastern Pacific warming (cooling).
The rapid development and persistence of the Philippine Sea wind anomalies result from interaction between
/atmospheric Rossby waves and ocean mixed layer thermodynamics. This interaction critically depends on the existence
of boreal cold season mean circulations. Therefore, the negative feedback proposed here favors the turnaround of ENSO
cycles in boreal winter.