Understanding Tide Coefficients

The tide coefficient is a numerical value that represents the amplitude of a tide – essentially how extreme the difference is between high and low tide. This value helps fishermen, sailors, and coastal visitors understand tidal patterns and plan activities accordingly.

What is a Tide Coefficient?

A tide coefficient is a value that represents the relative strength of a tide's amplitude compared to the mean spring tide range. The higher the coefficient, the greater the difference between high and low tide.

Key fact: Tide coefficients typically range from 20 to 120, with higher values indicating stronger tidal movements.

How We Calculate Tide Coefficients

  1. Determine Tidal Ranges:

    We calculate the height difference between consecutive high and low tides.

  2. Calculate Average Range:

    We take the average of these height differences to establish the day's average tidal range.

  3. Compare to Standard:

    We compare this average range to a reference value, which is the mean spring tide range (a standard value based on historical data).

  4. Calculate Coefficient:

    The coefficient is calculated as: (Average Range ÷ Mean Spring Range) × 100

Example: If the average tidal range for a day is 2.8 feet, and the mean spring tide range is 4.0 feet, the tide coefficient would be (2.8 ÷ 4.0) × 100 = 70.

Coefficient Interpretations

Strong Spring Tide (≥90)

Maximum tidal range with very high high tides and very low low tides. Strong currents and significant water movement.

Moderate Spring Tide (70-89)

Above average tidal range with pronounced high and low tides. Good water movement and current flow.

Average Tide (50-69)

Normal tidal range with moderate difference between high and low tides. Typical current strength.

Moderate Neap Tide (30-49)

Below average tidal range with less pronounced difference between high and low tides. Reduced current strength.

Weak Neap Tide (<30)

Minimum tidal range with little difference between high and low tides. Weak currents and minimal water movement.

Spring and Neap Tides

Spring Tides

Spring tides occur during full and new moons, when the Sun, Moon, and Earth are aligned. Their gravitational forces combine to create higher high tides and lower low tides.

  • Higher tide coefficients (>70)
  • Greater tidal range
  • Stronger currents
  • Occur approximately every 14 days

Neap Tides

Neap tides occur during quarter moons, when the Sun and Moon are at right angles to each other. Their gravitational forces partially cancel out, creating lower high tides and higher low tides.

  • Lower tide coefficients (<50)
  • Smaller tidal range
  • Weaker currents
  • Occur approximately every 14 days

Implications for Fishing

Many experienced anglers prefer fishing during moderate to strong tide movements (coefficients 50-90) when water movement stimulates fish feeding behavior. However, extremely strong tides (>100) can sometimes make fishing challenging due to very fast currents.

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