Lunar tidal tendency

Spring and Neap Tide Rhythm

Watch the broad tide-generating rhythm strengthen near new and full moons, then soften around the quarter moons.

Thursday, 8 October 2026

🌘 Spring-tide tendency

80%relative lunar tendency

Peaks indicate a stronger spring-tide tendency; troughs indicate a gentler neap-tide tendency. The percentage is a visual rhythm index, not a predicted water height.

The geometry

Alignment changes the range

At new and full moon, the Sun, Earth and Moon are nearly aligned. Their tide-generating effects reinforce one another, producing the broader spring-tide pattern.

At first and last quarter, the Sun and Moon appear roughly at right angles from Earth. Their effects partially offset one another, producing the more moderate neap pattern.

“Spring” does not mean the season. The older term describes the water “springing forth” through a larger tidal range.

Spring and neap tide geometryAligned Sun, Earth and Moon for spring tendency; a right angle for neap tendency. SPRING TENDENCY NEAP TENDENCY 90 degrees new or full moonfirst or last quarter
From gravity to a real coastline

Why your harbour will not follow this curve exactly

The broad signal

The Moon and Sun create the repeating astronomical tendency shown above.

Basins reshape it

Continents, seabed depth, bays and estuaries alter the timing and size of the moving tidal wave.

The observed level

Wind and air pressure can lift or suppress water beyond the astronomical prediction.

Learn more from NOAA: What are spring and neap tides? and why local high tides do not simply follow the Moon overhead.