The native Maoris call New Zealand "Aotearoa," or "Land of the Long, White Cloud." It's an apt name, because no day passes here without clouds--and everything below is affected by them.

"It's all about clouds," said Bob Rice, who for three years has charted and studied weather for America's Cup defender Team New Zealand, trying to make sense of winds that will fuel one boat to victory in the 30th America's Cup.

"Each cloud is its own little weather system," said Rice, 68, a New Englander who for 20 years has analyzed weather for high-profile attempts to sail or balloon across oceans or around the world. "Everything that happens, happens in these little patches."

For sheer complexity of wind and weather, Rice reckons no place on earth that sailboats regularly go matches the Hauraki Gulf, where since October a dozen teams have competed to narrow the field to the three still battling for the Cup--Team New Zealand and challengers AmericaOne and Prada. In six weeks it will all be over.

It is early summer here, not quite warm enough to put away the fleece jackets, like May in Washington. Auckland lies at Latitude 37, similar to Washington, but it is on the bottom of the world, so everything is backward. The sun cuts its arc across the northern sky, and to the south lie cold winds, the Roaring Forties, Antarctica.

All three surviving Cup teams collect weather data daily from the course, then crunch the numbers in computers to try to answer the fundamental question that has decided more races here than all others combined: Where will the next wind shift come from?

"It seems like every press conference I've been to, the winner said the reason he won was he got the first shift," said Ken Read, helmsman of Stars & Stripes, the last challenger eliminated from the regatta. Read should know. He picked the first shift incorrectly Friday and wound up so far behind America True, his fight was over by the first turning mark.

So what is this business of shifts and clouds and complex weather? If it revolves around clouds, it made sense to ask a man named Clouds. No one calls Roger Badham anything else.

Badham is a barefoot, balding, brilliant, bearded Australian with a doctorate in numerical meteorology. He lives in front of a laptop computer and travels the globe analyzing wind for sailors. His last job was as weatherman for Paul Cayard's EF Language, which won the 1998 Whitbread 'Round-the-World Race. Now he's with Cayard's AmericaOne, trying to add the America's Cup to the trophy case.

He agrees with his archrival down the road, Rice, that the Cup course is the most complex of weather places, with so many variables it's tempting to simply label the whole picture chaotic or random.

At Latitude 37, he said, New Zealand is in the clash zone between warm tropical highs to the north and cold Antarctic lows to the south. It separates two oceans--the chillier Tasman Sea to the west and warmer Pacific to the East. It's a land mass plunked in the middle of the sea, with Australia more than 1,000 miles one way and Chile 6,000 miles the other.

It lies north-south, with mountains, which is why it's the Land of the Long, White Cloud. Marine weather systems sweeping in from the west hit the ridges, rise, cool and form vapor. If there is no weather system around, sea breezes develop as the land warms, and the breeze can come from either direction--the Pacific or the Tasman.

All these factors generate wind, which when it hits the Hauraki Gulf must sculpt a way around islands, many volcanic and therefore steep.

"If you could only see the wind," mused Badham, "you'd see the most wonderful patterns. The vortices and eddies take on patterns all their own," which he described as random, but "predictable in their array."

Like water flowing over an irregular streambed, wind flowing into the Hauraki Gulf forms patterns, complicated by omnipresent clouds which suck air as they form or blow it down as they dissipate. Badham's job is to see the invisible patterns and mark them.

The weather teams from Prada, AmericaOne and Team New Zealand all have the same duty: To tell the skipper what to expect as the day goes on and tell the tactician 5 1/2 minutes before the start where the next shift is likely to come from and which way up the course, right or left, the stronger, or more favorable, pressure lies.

Five minutes before the start, communication with race boats ends by rule and the sailors are on their own.

Weather teams are secretive about how they gather and pass the vital information, but the pattern is to station data-collecting chase boats at corners of the course, which transmit information to a powerful computer on the main tender near the start.

The weatherman passes it along with his observations, and the tactician, in his wisdom, must decide whether to fight for the right or left side of the starting line. If he picks correctly and the helmsman does his job and wins that side, the wind should give him a better angle to the first mark. When it shifts back, he can tack and cross the other boat.

Once you're ahead in this America's Cup, the battle is half-won as the boats are very close in speed.

So far, the king of the first shift in the trials has been AmericaOne. Badham and tactician John Kostecki picked the right way to go 9 of 10 times in the semifinals, and Cayard won the starts. AmericaOne had the best record at 8-2.

Now comes the best-of-nine challenger finals with Prada, the swift silver-and-red racer from Punta Ala, Italy. By most accounts, Prada is slightly quicker than AmericaOne, but Cayard's team is more experienced and skillful. Once again it will likely come down to the first shift--whether Cayard gets it and holds off Prada's charge or Prada gets it and sails away.

In February, the winner faces Team New Zealand. Two weeks later it will all be over. The tricky winds can blow unscrutinized again, as they have for millenia, carving invisible patterns under the long, white cloud.