The warmer phase of ENSO happens when:

The warmer phase of the El Niño-Southern Oscillation (ENSO) occurs when the trade winds weaken. During a typical state, strong trade winds blow from east to west across the Pacific Ocean, which helps to pile up warm surface water in the western Pacific. When these trade winds weaken, the warm water that is usually concentrated in the western Pacific flows back towards the central and eastern Pacific. This shift in warm water significantly changes oceanic and atmospheric conditions, leading to the El Niño phase of ENSO, characterized by increased sea surface temperatures in the central and eastern Pacific.

This phenomenon can impact global weather patterns, resulting in changes such as increased rainfall in some areas, droughts in others, and can even affect marine life due to the altered ocean conditions. Understanding the dynamics of these trade winds is crucial for predicting weather patterns related to sailing, flying, and other outdoor activities, as it influences various climate variables.