Diurnal Tide

A diurnal tide is a tidal regime with one high water and one low water each lunar day of about 24 hours 50 minutes, governed by the diurnal constituents K1 (23.9345 h) and O1 (25.8193 h) rather than the semidiurnal M2. It dominates parts of the Gulf of Mexico, the South China Sea, and northern Australia. The form number F, the ratio (K1 plus O1) over (M2 plus S2), exceeds 3.0 for a diurnal regime. Tide tables for diurnal ports list one high and one low per day, and the daily range can collapse near lunar zero declination when the diurnal forcing weakens.