MarkGeldmeier's Blog

Dave went to Hawaii in April and I was there in March. Being back in Hawaii reminded me of some of the interesting features of weather in the "sub-tropics". Here's one of them;

In the mid-latitudes (which includes Missouri and Illinois), the prevailing winds are West to East, and our weather systems travel generally from West to East. In the sub-tropics, things move in the opposite direction! The "Trade Winds" in Hawaii blow out of the ENE and are very consistent. The strength of the "Trades" might vary, but 8 out of 10 days will include the wind from this direction.

Because the wind is almost always blowing from the same direction, there are several local features that result from the constant breeze. For example, trees always "lean" the same direction and the volcanic cones are higher on the west side (since the material was blown this way when it erupted). The island of Maui is shaped like a "dumb-bell", with two mountain peaks connected by a valley in the middle. The island is aligned such that the mountains funnel the Trades through the interior valley section. The southern mountain, Hale’akala, is much taller, so the affect is that winds accelerate across the middle of the island and then spin around on the "leeward" or down-wind side of the island. This nearly constant spinning mass of air has been called the "Maui Vortex". From the town of Kula on the western slope of Hale’akala, you can watch the low clouds slowly spinning like a huge whirlpool. Sometimes, the smoke from burning sugarcane fields will drift over the ocean but then circle around and move back over the island.

So the next time your lying on Maui’s Makena Beach and you notice that the sky is spinning. Sure it might be too many Mai Tai’s! But then again, it just might be the Maui Vortex!

*I was searching the internet for a good satellite loop that would illustrate this, but haven’t yet found the right resolution and animation. If someone can find a possible site – please let me know!