Tropical Instability Waves are a prominent feature in analyses of tropical Pacific sea surface temperature and sea level height variability, and may play a significant role in the heat, salt and momentum budgets of the equatorial oceans. Here we show that they may be strongly influenced by forcing from the atmosphere. In experiments with an ocean GCM we find that a phase shift in the subseasonal wind forcing gives rise to a corresponding phase shift in the TIWs, indicating a systematic influence of the high frequency wind forcing. ¿ 2001 American Geophysical Union