The 6-meter NOMAD buoy

NDBC's station pages name six of Bluegraph's stations as 6-meter NOMAD buoys owned and maintained by Environment and Climate Change Canada (ECCC): off Nova Scotia, 44150 La Have Bank (1,300 m of water), 44137 East Scotia Slope (4,000 m) and 44139 Banquereau (1,500 m); off British Columbia, 46004 Middle Nomad (3,600 m), 46036 South Nomad and 46184 North Nomad. Bluegraph counted them from those pages in October 2026.

The pages may be out of date. A 2021 paper by scientists at the U.S. Army Corps of Engineers, ECCC and NDBC says that ECCC decommissioned its last NOMAD in 2019 and replaced it with a 3-meter discus, and ECCC's description of its network lists 3-meter discus buoys on the coasts and none of this hull. Fisheries and Oceans Canada still listed the three Pacific stations as NOMADs in 2023, and ECCC's own page on buoy observations still describes the hull. Some or all of the six may now be ECCC's 3-meter discus buoys, which carry the same payload and report the same way.

NOMAD stands for Navy Oceanographic Meteorological Automatic Device. The U.S. Navy built about 20 of these hulls in the 1950s, and NDBC later took them into its network; one rode out Hurricane Carla in 1962, in winds estimated at 67 m/s. For Canada, Seakem Oceanography of Sidney, British Columbia (now part of AXYS), built five aluminum hulls based on NDBC's models, and the first two were deployed in September 1987, at the North and South Nomad stations. Canada's network had at most eight.

The hull is welded aluminum, 6 m long and 3.1 m wide, with an aluminum superstructure and a steel substructure bolted on. NDBC's NOMAD measured 6.1 m long, had a draft of 1.49 m and stood 0.64 m out of the water. Inside are four watertight compartments for the electronics, batteries and sensors. It weighs 5,200 kg without ballast, and carries up to 1,360 kg of lead in a keel under the hull and up to 2,720 kg more inside; ECCC gives 8,000 kg deployed.

ECCC moors it up to 400 nautical miles offshore, in 3,200 to 4,000 m of water, on an inverse-catenary mooring: a line buoyed up along part of its length, so that it has slack for the hull to ride the waves and swing around. Two of Bluegraph's six are in shallower water than that, 1,300 and 1,500 m. The mooring hangs from a yoke under the bow, which is rigid in the roll plane.

Moored by the bow, the hull swings like a ship at anchor until it points into the wind and, usually, into the waves. NDBC calls it highly directional, with a quick rotational response. Facing into the waves, it pitches more than it rolls; lying across the waves, as it does while it swings, it rolls. Its weight is carried low, so it can roll far over and come back upright: NDBC knows of no NOMAD that capsized, and turned to this hull after its 10-meter discus buoys capsized in extreme storms.

NDBC's NOMAD has natural periods of 2.4 s in pitch and 3.8 s in roll, shorter than most ocean waves, so it rises and falls with the longer waves almost as the water does. Waves only a few times the hull's length are averaged out over the hull, and move it less than they move the water. Its motion gives a good measure of how high the waves are, but not of the direction they come from: directional waves are difficult to measure on this hull, and ECCC reports none from it.

ECCC's buoys carry AXYS Technologies' Watchman, which samples the sensors, calculates the readings and sends them to shore: the Watchman 100 by GOES satellite and, since 2021, the Watchman 500 by Iridium. It is powered by primary batteries and by batteries charged by solar panels on the foredeck.

Two anemometers stand on a forked mast toward the stern, about 5 m above the water, and the national archive of these buoys' readings keeps a second set of wind readings and a second pressure reading beside the first. A forward mast carries the navigation light, a radar reflector and the satellite antenna. The air and sea temperature sensors and the barometers are not shown in the builder's photograph, and their heights are not published, so the figure doesn't draw them.

The Watchman measures waves with an accelerometer strapped down in the hull. Each hour, it records the hull's vertical acceleration once a second for 2,048 s, about 34 minutes. From that record, the payload calculates a spectrum in 41 frequency bands, from 0.0039 to 0.4812 Hz, and from the spectrum the significant wave height, the highest wave and the peak period. ECCC describes the wave height and period as averaged over 30 to 35 minutes each hour.

Compared with a Datawell Waverider moored within 19 km of it off Monterey, California, a NOMAD with a Watchman measured the significant wave height reasonably well up to about 6 or 7 m, and above that read low by up to about 1 m. An earlier comparison against satellite altimetry found a systematic difference of about 10% between ECCC's wave heights and NDBC's. Bluegraph shows the wave height and dominant period that NDBC relays from these buoys. They report no wave direction or average period, and NDBC publishes no spectra for them, so Wave Intelligence doesn't cover them.

ECCC gives the wind speed as a 2-minute mean before the hour, and the gust as the highest in the 10 minutes before the hour. The anemometers are about 5 m above the water, higher than the 3.8 m on NDBC's 3-meter discus buoys, which matters when comparing the two. As NDBC relays them (October 2026), the speeds are in whole meters per second and the directions in tens of degrees.

Pressure, air temperature and sea temperature are the latest values on the hour. Bluegraph shows them as NDBC relays them, with the 3-hour change in pressure; these buoys report no dew point.

Each buoy reports once an hour, by GOES or Iridium satellite. Fisheries and Oceans Canada's Marine Environmental Data Section archives the reports, and NDBC relays them; Bluegraph collects them from NDBC.