Meteorologist Malika Dudley Explains “Trade Wind Weather”
Aloha, I’m meteorologist Malika Dudley and today we are flying in a Blue Hawaiian Helicopter to get a great vantage point of Maui. Today, we are talking about our prevailing winds and the weather it produces.
When the wind encounters land it interacts with it. Here in Hawaii, a majority of the time winds blow out of the northeast or east. The weather pattern that results is what people refer to as “trade wind weather”.
The winds are moving in from over the ocean and our mountains are huge barriers for this air. As the air passes over the barriers it is orographically lifted.
In simple terms, the air rises and cools so clouds form along the slopes. These clouds bring moisture or rain to the windward side of our mountains.
Here on Maui, rainfall is strongly affected by two volcanic peaks: Haleakala and Pu’u Kukui (the summit of West Maui Mountains).
Pu’u Kukui is cone-shaped so orographic lifting occurs from all sides. The deep valleys help to funnel air toward the summit so Pu’u Kukui actually gets more rain than any other spot on Maui.
The peak of Haleakala is different because it’s above the inversion layer. That is where the air is so dry that any clouds that are able to get through the layer evaporate quickly. This prevents moist air from getting to the summit keeping conditions really dry up there. When you fly with Blue Hawaiian Helicopters, you can clearly see where the inversion layer is. Above that point, there are no clouds.
The leeward sides of Haleakala and the West Maui Mountains tend to also be dry. After orographic lifting essentially squeezes the moisture out of the clouds on the windward side when the air subsides or sinks down on the leeward side what’s left is warm and dry air. The leeward side is in the rain shadow creating a dry zone.
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