🌊 The Biddeford Pool Wave Buoy

Wave height

What it is: "Significant wave height": the average height of the biggest third of the waves, trough to crest. It is close to what an experienced sailor would estimate by eye.

Why it matters: Wave height drives beach erosion, coastal flooding and safe boating. A few big storms each year do most of the work of moving sand along the coast.

📏 Under 1 ft: calm. 1–3 ft: normal. Over 3 ft (1 m) for hours: a storm event here. Single waves can be about twice the significant height.

📍 Here: typically 1.8 ft; biggest so far 10.4 ft. A "storm event" on this page = waves ≥ 3.3 ft (1 m) for 6+ hours.

Wave period (rhythm)

What it is: Seconds between one wave crest and the next.

Why it matters: Short-period waves (under ~6 s) are choppy and made by local wind. Long-period swell (10 s or more) was made by a distant storm, carries much more energy for its height, and reaches farther up the beach.

📏 Tip: count the seconds between waves at the beach — that is the period.

Wave direction

What it is: The compass direction the waves are coming from (like wind direction).

Why it matters: Direction decides which beaches take the hit and which way sand is pushed along the shore.

📏 "E" means waves rolling in from the east.

Wave energy

What it is: How much energy the waves carry toward shore, per metre (or foot) of coastline. It grows with the square of wave height and with the period.

Why it matters: It is the best single measure of how hard the ocean is working on the coast — useful for erosion studies.

📏 1 kWh ≈ running a microwave for an hour.

Air pressure

What it is: The weight of the air above, in hPa (hectopascals) or kPa (1 kPa = 10 hPa).

Why it matters: Falling pressure usually means a storm or front is coming; rising pressure means clearing weather. Very low pressure also lets the sea rise a little higher (storm surge).

📏 ~1013 hPa (101.3 kPa) is average. Under ~1000 hPa usually means a storm.

Wind

What it is: Average wind speed, the strongest gust, and the direction the wind is blowing from.

Why it matters: Wind builds waves, pushes water against the shore, mixes oxygen into the water and dries out soils.

📏 Light: under 10 mph. Breezy: 10–20 mph. Strong: 25+ mph. Gale: 39+ mph.

📍 Here: this buoy has no wind vane — it estimates wind from the shape of the waves, so treat it as approximate, especially in light winds.

Water temperature

What it is: How warm or cold the water is, measured by a sensor just below the surface.

Why it matters: Temperature controls almost everything in the water: how much oxygen it can hold, how fast algae grow, which fish and shellfish are comfortable, and when lobsters and other animals move or molt.

📏 Gulf of Maine coastal water runs roughly 38–45 °F (3–7 °C) in late winter and 60–68 °F (15–20 °C) in late summer. Shallow ponds and marshes swing much more, warming fast on sunny days.

Current

What it is: How fast and in which direction the water itself is moving, measured below the buoy.

Why it matters: Currents carry larvae, nutrients, sediment and pollution, and matter for swimmers and boaters.

📏 Tidal currents here typically reach a few tenths of a knot; 10 cm/s ≈ 0.2 knots.

Tide / water level

What it is: The height of the water surface. Along the Maine coast the sea rises and falls about 9 feet twice a day (every ~12 h 25 min), pulled by the Moon and Sun.

Why it matters: The tide moves water — and everything in it — back and forth past a sensor, so many readings change with the tide. In marshes and ponds, water level shows how often the tide floods in and how high storms push it.

📏 Heights on tide charts are measured above average low tide (MLLW). Storms and strong onshore winds can push water higher than predicted.