How do the southeast trade winds affect Papua New Guinea’s rainfall?

In Papua New Guinea, rainfall is primarily determined by two wind systems, one of which is the southeast trade winds. These winds typically blow for about seven months of the year, from May to November, though their duration varies by location.1

The impact of these winds on precipitation is heavily dependent on local exposure and topography:

• Coastal Effects: In areas where the winds flow parallel to the coast, such as the region around Port Moresby, the landscape remains parched and receives very little rainfall.1
• Mountainous Effects: Where mountainous terrain lies directly in the path of the airflow—such as on the island of New Britain or the southward-facing slopes of the Highlands—the winds force air upward, resulting in extremely heavy precipitation that can frequently exceed 300 inches (7,600 mm) annually.1

Ultimately, while the southeast trade winds are a major climatic control, their influence on whether a specific area experiences drought or heavy rainfall is dictated by how the land is positioned relative to the wind's path.1