One Ocean, One People

2007 Voyage to Micronesia and Japan

A Celebration of Pacific Voyaging, Cultures, and Islands


Navigation and the Natural Environment

Last Update: October 31, 2006

Navigtors of the Polynesian Voyaging Society guide the voyaging canoe Hokule’a on the open ocean without instruments, by natural signs. (For a summary of techniques, see Wayfinding, or Non-instrument Navigation at the PVS website.) This kind of navigation requires a knowledge and careful observation of the natural environment for clues to direction, landfall, and potentially dangerous situations.  Below is a description of the 2007 Natural Environment of the voyage to Micronesia and Japan, including the Heavens (Celestial Bodies, Winds, and Clouds); Ocean (Swells and Currents); and Sealife: Bird and Fish.

Links:

The Skies and Heavens 

Winds

The voyages to Micronesia and Japan are timed to avoid the Pacific season of typhoons (tropical cyclones, called hurricanes in the Atlantic), from May through November. Typhoon force winds could destroy the canoe and place the crew at considerable risk. Typhoons are most frequent from July to October averaging up to five per month.  They may increase in frequency during the warm phase of the El Nino Southern Oscillation (ENSO), when sea surface temperatures warm in the central and eastern Pacific. (For more on hurricanes, see “Tropical Cyclones” (Wikipedia); “Pacific Typhoon Season” (Wikipedia) provides historical data on the season.

Hokule‘a will depart Hawai‘i for Micronesia in January, after the 2006 typhoon season ends, and complete its voyage in Japan in May, before the start of the 2007 typhoon season.

Winds in the Western Pacific (from Sailing Directions)

Hawai’i: In January, when Hokule’a is planning to depart, the North Pacific anticyclone (an area of high pressure) has repositioned itself, so that the trade wind weather that prevails during the summer months becomes less dominant and the winds more variable, Still, trade wind weather prevails about 42% of the time, with an average of nine days of strong winds. The canoe plans to ride the easterly winds west to the Marshall Islands and Micronesia.

Republic of the Marshall Islands and the Federated States of Micronesia: From December to April, trade wind weather prevails: ENE to Easterly winds blow almost constantly, averaging 8-12 knots.

Republic of Palau: During the NE Monsoon (November through April), the prevailing winds are ENE, with a frequency of 93 percent in January and 82 percent in April. The average velocity is 12 knots in December through February, and from 8 to 10 knots for the remainder of the period. Calms occur from 5 to 10 percent of the time. Gales occur very rarely.

Okinawa: Late January, February, and March are cool and wet, and then the nice weather returns in April. Winds are easterly for greater part of April and May (trades), gentle (7-10 knots) to moderate breezes (11-16 knots). April temperatures in Naha Okinawa range from 66-77 degrees F.

Kyushu and Southern Honshu: The weather in Kyushu and Southern Honshu is mild in April and May. Winds are generally light (gentle and moderate breezes), with direction affected by the proximity of land and islands. Temperatures from Fukuoka to Tokyo range from 51-67 degrees F in April; and 59-74 degrees F in May.

Clouds

The lower clouds move in the direction of the surface winds. The higher clouds may be moving in a different direction because the winds in the upper atmosphere may be blowing in a different direction from the surface winds.

Oncoming clouds are predictors of weather because various clouds are associated with various kinds of wind and weather conditions. For example, cumulus clouds are associated with fair weather; nimbostratus clouds with rain and poor visibility, which makes navigating by the starts impossible, so the navigator must guide the canoes by the ocean swells; cumulonimbus clouds (Wikipedia) with storms. A line of cumulonimbus is called a squall, which brings strong winds. When the navigator sees a squall line approaching, he or she may order the sails closed up to prevent damage to the sails, rigging, or mast.

The colors of the clouds or the sky around clouds can also be used to predict weather. Red skies at sunrise or sunset indicate moisture in the atmosphere and possibly rain or squally weather. Gray skies at the horizon indicate strong winds (the gray is sea water whipped up by the surface winds and is called “smoke.” Mau Piailug notes, "If the rain cloud is black, the wind isn't strong. If the cloud is brown, the wind is probably strong. If the cloud is high, there's not much wind, but maybe a lot of rain. If it's low, probably lots of wind. (For more on forecasting weather without instruments, see “Non-Instrument Weather Forecasting (PVS website).

For a comprehensive classification of clouds and their character and characteristics, see “Clouds” at Wikipedia.

Celestial Bodies Used in Navigation

Chiefs among the guideposts to direction on the open ocean are the rising and setting sun, moon, and stars. These celestial bodies rise and set in one of 24 directional houses of the Hawaiian star compass developed by Nainoa Thompson (explanation of directional houses), based on the Micronesian star compass of Mau Piailug

Sun: From January-March, while Hokule’a is sailing from Hawai’i to Satawal, the rising point of sun moves on the eastern horizon from the House of ‘Aina Malanai (ESE) in January, to La Malanai (E by S) in February, to Hikina (East) in March

The setting point on the western horizon moves, from the House of ‘Aina Kona (WSW) in January, to La Kona (W by S) in February, to Komohana (West) in March 

From April-May, while Hokule’a is sailing from the Northern Marianas to various ports in Japan, the rising point of sun moves on the eastern horizon from Hikina (East) in March-April to the House of La Ko’olau (E by N) in April-May; the setting point moves on the western horizon from Komohana (West) in March-April to the House of La Ho’olua (W by N) in April-May.

Moon: The rising points of the moon changes nightly, moving between the House of ‘Aina Malanai (ESE) and the House of ‘Aina Ko’olau (ENE) during the 29.5 day lunar cycle; the setting point changes nightly as well, but is always between the House of ‘Aina Malanai (WSW ) and the House of ‘Aina Ho’olua (WNW). While less exact that the stars whose rising and setting points remained fixed, the moon, because of its brightness, is used when more exact guideposts are hidden by clouds. The border between the bright and dark side of the moon is oriented generally north-south.

Stars: The stars, like the sun and moon, rise at the eastern horizon and set at the western horizon at fixed directional points at given latitudes. As the sky darkens at sunset, the stars appear to rise from the eastern horizon and set at the western horizon, moving at the same speed as the sun and the moon, because the movement of these celestial bodies is determined by the rotation of the earth. (The sun, moon, and stars are not rising and setting; they only appear to do so because the earth itself is rotating toward the east.)

The navigator uses sets of stars, called star lines, that rise and set around the same time; a different set might be used at different times of the night or the year. (For a description of the four star lines used by Hokule‘a’s navigators, and the stars included in the star lines, see “Starlines and Declinations.”

From January-March, while Hokule’a is sailing from Hawai’i to Satawal, the rising star lines are (1) Iwikuamo‘o, the Backbone, and (3) Manaiakalani, Maui’s Fishhook; the setting star lines are (1) Ka Lupe o Kawelo, the Kite of Kawelo (including the great square of Pegasus), (2) Ke Ka o Makali‘i, the Bailer of Makali‘i.

From April-May, while Hokule’a is sailing from the Northern Marianas to various ports in Japan, the rising star lines are (1) Manaiakalani, Maui’s Fishhook, and (3) Ka Lupe o Kawelo, the Kite of Kawelo (inlcuing the Great Square of Pegasus); the setting star lines are (1) Ke Ka o Makali’i, the Bailer of Makali‘i and (2) Iwikuamo’o, the Backbone.

Northern Sky: Above the northern horizon, the North Star or Polaris (Hokupa’a, or fixed star in Hawaiian) is the main guidepost in the Northern Hemisphere. (The North Star cannot be seen in the Southern Hemisphere, as it is below the horizon.)

In the northern sky, the stationary star above north is the North Star; the other stars appear to rotate around it. The altitude of the northern star is approximately equal to the latitude of the observer in the northern hemisphere. For example, at 20-21 degree north (Hawai’I), the star appears about 20-21 degrees up from the horizon on the celestial sphere. In Micronesia, around 5-10 degrees north, the star is about 5-10 degrees up from the horizon. In southern Japan, at 25-35 degrees north, the star appears 25-35 degrees above the horizon. Thus the altitude of the North Star can give the navigator an approximation of latitude (but not longitude.)

The constellations rotating around the North Star include ‘Iwakeli‘i (Cassiopeieia) and the Little Dipper with Holopuni (Kochab) in it. As a star takes 24 hours, or one rotation of the earth, to make a circuit around the North Star, the changing positions of a star or constellation around the North Star can be used, like the hour hand on a clock, to estimate time. When it is on the opposite site of the North Star, 12 hours have passed.

Southern Sky: Hanaiakamalama, the Southern Cross, is most useful guidepost in the southern sky. When upright, it points due south.  From January-March, while Hokule’a is sailing from Hawai’i to Satawal, the southern cross rises in the late evening SSE; and in the early morning darkness, it points due south.

In April, while Hokule’a is sailing from the Northern Marianas to Okinawa, Hanaiakamalama rises after sunset S by E and points South at night. By the time the canoe is in southern Honshu, only the top portion of the cross is visible; by the time the canoe is in Yokohama (36.5 degrees N), Hanaiakamalama is no longer visible. (After arriving in Kyushu and Honshu, the canoe will be coastal sailing in sight of land and will no longer have to navigate by the stars.)

Ocean

Wind Force and Sea State: The strength of the local wind affects the sea state and wave activity around the canoe. “Sea State Photographs for Determining Wind Speed / The Beaufort Wind Force Scale (from NOAA)” (Geosciences Department of Western Michigan University website), illustrates the varying sea states based on the strength of the wind creating each one, from Force 0 (calm wind speed less than 1 knots) to Force 11 (Wind speeds of 56-63 knots), which is considered a violent storm. Winds above 63 knots (72 miles per hour) are considered hurricane force. Wave heights are given in meters (1 meter = 3.3 feet); winds speed in knots, or nautical miles per hour (1 nautical miles = 1.15 miles). The categories of force are from the Beaufort Wind Force Scale.

Swells: Swell patterns are used for navigation. Swells are created by stable wind activity that persists over a period of time. Swells maintain their directions over long period of time. You can determine which direction swells are coming from or heading to in relationship to the rising and setting sun, or from rising and setting stars. A swell coming from the ENE will appear to be coming from four directional houses to the left of the rising sun in January, when the sun rises ESE; the ENE swell appears to head toward the setting sun, which sets WSW. The navigator aligns the canoe to the direction he wants to head in relationship to the swell. By March 21, when the sun is rising E and setting W, the ENE will appear to be coming from two houses the left of the sun, and heading toward two houses to the left of the setting sun.

Currents: Currents run at and under the ocean surface. Above 10 degrees North, the North Equatorial Current flows west at about 0.5 knots, the surface of the water pushed along by the prevailing trade winds. Closer to the equator is the Equatorial Countercurrent, which flows east, the water pushed to west by the trade winds flowing back east; this current is generally weak and unpredictable. The west flowing current will help move the canoe along as she heads west to Micronesia. On a north-south route, this westerly current will set the canoe to the west of the direction it is headed; so the navigator takes the current set into account by pointing the canoe slightly to the east of the destination.

Sailing Directions has this warning about currents around islands in the Western Pacific: “Particular and constant attention must be paid to the currents when navigating amongst the island groups. As a rule these currents are deflected and always strengthened near the islands. Strong currents are found in the narrow passages.”

Sea Life

Sea Birds: Sea birds are used to find land. However, not all seabirds are useful for finding land. The birds that are most useful are the birds that fly out to sea in the morning to fish and return to their home island at night to rest Thus, at dawn the direction the birds are coming from may indicate the direction of an island; the direction the birds are going to in the afternoon indicates the direction of an island.

The two most reliable land-finding birds are the manu o Ku, or white tern and the noio, or noddy tern. See “Fish, Birds, and Mammals of the Open Ocean” (PVS website). For more on these two birds, see the following Wikipedia sites:

Other birds are sighted in the Pacific open ocean. As these birds may stay out at sea for more than a day, soaring and fishing (and some live most of their lives on the open sea, except when they breed on land), the direction of their flights does not necessarily indicate the direction of land. For information about open ocean seabirds, see the following Wikipedia links:

Edible Pelagic Fish of the Pacific Ocean: The crew of the Hokule’a deploys fishing lines when voyaging and catch various fish for consumption. Although seafearers have been known to eat seabirds when no other food is available, fish is the preferred fresh meat because it generally tastes better. Among the fish considered ono, or delicious and best for eating are the aku (skipjack tuna), ahi (yellowfin tuna), mahimahi and ono (wahoo). See “Fishing Aboard Hokule'a” at the PVS website.

For more information about the edible fish caught on the open ocean, see the following Wikipedia links: