Thorsten wrote in Tue Sep 13, 2011 6:53 am:
Maui happens to be one of my testbeds for placement of thermals (because the terrain changes radiacally over short distances), but since I've never been there, I am down to plausibility. Here
are some recent developments of how the conditions are simulated right now.
Man, that is gorgeous scenery! How did you do that? Maui sure doesn't look that good on my system.
Anyway, the clouds around Haleakala are typically very dense by mid morning on the north side (left in the pic). They don't "ring" the mountain, but hit it from the northeast and back up out to sea. Meanwhile, the tops, when they reach the height of the crater rim, spill over almost like a waterfall, down the leeward side of
the crater rim, and dissapate within the crater itself. The leeward side is typically cloudless, and gusty.
What's spectacular is how the clouds re-form on the leeward rift that runs from the southwest corner of the crater (the summit). At about 5 to 6,000 elevation, they form, almost as if they're coming right out of the mountain itself. The form something like a train of clouds that gets thicker as they head out to sea. It's really quite a sight to be standing on the mountain, and seeing the clouds form just a few hundred yards in front of you. The effect is like the sky spinning cotton candy.
Looking at the maps behind the link provided by Wilbur1, I can see it's happening at the edge of a very strong wind "apron" that edges to the south east coast
of the island. That coast is typically very gusty. It's also virtually uninhabited because (according to locals) the wind. It's dry, windy, and empty.
All the islands have lots of distinct microclimates, with dramatic changes in climate happening in distances of less than a mile. The valleys of west maui that open
onto the south-southwest shores have very pronounced winds that can be dangerous to motor vehicles, and a sailor's delight. I remember riding along the coast
road on a motorcycle, and as the road turned into a valley, the wind would hit you like a brick at first. The road would follow the side of the valley downhill,
but because of the wind, you'd slow down if you didn't add throttle. Then as you turned, the wind was coming from the outside of the turn, so you could go
a LOT faster than your eyes would allow you to think, and then ZIP up the hill with the wind to your back. If you didn't know how it worked, it could be
FWIW, most air traffic in Hawaii sticks to over the water to the north of the islands. I've flown a bit in an 8 passenger cessna (410?) and it's amazing how
the wind changes dramatically when you cross an invisible, but predictable "line". It gets really bumpy when you start flying over the land. Likewise, on a
sailboat, there's a "wind line" they talk about, and you can almost see it as you cross over it in a boat. One minute the water's smooth (with swells), and
the next minute, it's blasting.
BTW, when you cross those channels, don't forget that the winds are all crosswinds. I have a hard time imagining crossing from Oahu to any other island, or Maui to the Big Island. The sailing conditions there are likened to rounding the horn of South America. You can see whitewater from 30,000. The Hawaiian name for that channel is "alenuihaha", which means "use great caution".
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