Module 11 - Tides & Tidal Streams
Springs and Neaps
When the Sun and Moon align (new moon and full moon), their gravitational pulls combine, producing spring tides — the highest highs and lowest lows. When the Sun and Moon are at right angles (first and third quarter), their pulls partially cancel, producing neap tides — smaller range between high and low.
Similar spring conditions recur roughly every 14–15 days. The local tide usually lags the astronomical alignment, but the lag and the difference between spring and neap range are port-specific. Perigee, lunar declination, coastal geometry, seasonal levels and weather can all affect the most extreme levels; some places have larger seasonal springs near an equinox, but that is not a universal rule.
- Spring tides — Sun and Moon aligned (new/full moon). Largest range.
- Neap tides — Sun and Moon at 90° (quarter moon). Smallest range.
- Spring/neap cycle ≈ 14 days
- Springs occur 1–2 days AFTER new/full moon
- Do not assume an equinox gives every port its largest spring range
Watch for this: Spring tides are NOT related to the season of spring. They 'spring' up to their highest.
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