To hear Hawaiian non-instrument navigator Nainoa Thompson tell it, for voyaging canoe Hokule'a skipper Bruce Blankenfeld to find Johnston Atoll would be a near miracle.

After two cold, cloudy nights, Blankenfeld yesterday was sailing a course that would pass north of Johnston, but close enough to be within the flight range of birds that return to land each night.

By yesterday afternoon, the crew on Hokule'a had spotted four manu o Ku — white terns — indicators of land.

The canoes may or may not actually sight Johnston — a low island easy to miss — but they know they are in its vicinity.

It is a testament, Thompson said, to both the remarkable skills of Blankenfeld and to the effectiveness of traditional wayfinding. For Thompson and Blankenfeld, it is also a key feature in the Hawaiian identity and a source of pride for a proud seafaring people.

"This voyage is very complex, very hard, but that's why it's such an extraordinary learning and teaching opportunity," Thompson said.

The voyaging canoes Hokule'a (Blankenfeld as skipper/navigator) and Alingano Maisu (Shorty Bertelmann as skipper and Chadd Paishon as navigator), along with escort boat Kama Hele, are nearly two weeks into a voyage into the western Pacific.

Blankenfeld is using a range of ancient skills that have carried Polynesian navigators on voyages that populated nearly every habitable island in the vast Pacific: reading ocean swells, gauging wind shifts, identifying sweeping currents, judging the clouds, spotting birds and marine debris, studying the stars, sun, moon and planets.

A SEASONED CREW

Thompson, Blankenfeld and a handful of other Hawaiian navigators have done this before. They have sailed Hawaiian double-hulled canoes throughout the Pacific by traditional means — as far east as Rapa Nui or Easter Island, and as far south and west as Aotearoa or New Zealand. Several of the state's most experienced navigators, including Thompson, Blankenfeld, Bertelmann, Paishon and Chad Baybayan, will participate in this mission, to deliver the Alingano Maisu as a gift to their navigation teacher, Satawal islander Mau Piailug in Micronesia, and then to sail Hokule'a on a goodwill mission to Japan.

In a satellite telephone conversation last week, a fatigued Blankenfeld said the navigation has been challenging from the start of this mission, which began Jan. 23 in Kealakekua Bay.

"The first couple of days were overcast, the wind was switching around. It was crazy," he said. "Now, instead of the wind being at our backs like we expected, we're tacking," he said. The wind last weekend began blowing from the southwest, the direction in which the canoes were hoping to be sailing.

Tacking involves sailing as close as possible to the wind, and then bringing the canoe's nose through the wind to put the breeze on the opposite side. Double-hulled voyaging canoes do not point very close to the wind, so the canoes must make long tacks to gain only a little distance. Extensive tacking also exaggerates errors, making it harder to judge one's position.

Thompson said the canoes have faced extremely difficult sailing for navigational purposes.

"You had the tradewind swell (from the northeast), a big north swell of 12 feet or more, plus local wind waves coming from the southwest. It's extraordinarily complex sea conditions, and you've got to be able to decipher the confusion. This is the most difficult thing: having to find one small island and tacking to do it," he said.

A SLEEPLESS JOB

It is difficult, too, because a traditional navigator keeps his or her position in his or her head and navigators tend to sleep in catnaps so they don't miss any changes. Thompson describes the extraordinary demands made on memory while in a state of semi-exhaustion, defining his desired course, and then keeping track of how far winds, currents, swells and steering errors have pushed the vessel off that track — and what needs to be done to bring the canoe back on track.

Thompson said that when sailing to Tahiti, errors are forgiven by the wide swath of islands of the Tuamotu, which give a navigator a target more than 400 miles wide. Reaching any one of them is marked a success. Sailing from Tahiti to Hawai'i, the target is the 300-mile-wide chain from Hawai'i to Kaua'i.

But finding a single island like Johnston Atoll, which is hundreds of miles from anywhere else, is quite a challenge.

"You'll pass that thing in an hour at night," Thompson said.

Traditional navigators have a couple of skills that help them in these cases, he said. One is birds — knowing that certain birds return to land each night.

Another skill involves knowing the latitude of a target — how far it is from the equator. While it is difficult for a sailor without a clock or electronics to determine how far east or west the boat is, it is relatively easy to determine latitude, which is how far north or south it is. A key indicator is the height of the Hoku Pa'a, the nearly stationary star known also as the North Star or Polaris. If Hoku Pa'a is 30 degrees above the horizon, then the boat is at 30 degrees north latitude.

Thompson said he expects Blankenfeld to put the canoe on the latitude of Johnston Atoll — just less than 17 degrees north latitude — and if possible sail directly eastward down the latitude. If he nears the island in daylight, he has a chance of seeing it.

On Friday, the contrary winds changed back to trades, and the canoes began sailing a more direct line toward the isolated atoll. The canoes won't stop, but the point of finding Johnston is that it is almost directly on the line between the Big Island and Majuro, and it's the only island on that line. So it serves as a confirmation that the course is correct.

Once he finds it, Blankenfeld will be able to sleep. At Johnston, the lead navigation duties switch to navigator Paishon on the canoe Alingano Maisu.

Reach Jan TenBruggencate at jant@honoluluadvertiser.com.