MET-O

• the periodic motions of waters of the sea due to differences in the attractive forces of various celestial bodies, principally the moon and sun, upon different parts of the rotating earth

  tidal phenomenon
• a periodic horizontal movement of the water

  tidal current
• British usage of tidal current is

  tidal stream
• the change in the water level the water moves toward the shore

  flood tide
• the change in the water level when the water moves away from the shore

  ebb tide
• rise and fall of the water level

  tide
• the periodic rise and fall of water in the ocean accompanying the tidal phenomenon.

  tide
• the maximum height reached by the ascending tide.

  high water or high tide
• the minimum level reached by the descending tide.

  low tide or low water
• the period at high or low water during which there is no sensible change of level


  stand of the tide
• when there is no more horizontal movement of the water, occurs between the flood and ebb

  slack water
• the difference in height between consecutive high and low waters

  Range of the tide
• the vertical distance at any time of the tide from the chart-sounding

  datum (charted depth)

  height of the tide
• the vertical distance from the chart-sounding datum to a high tide reference point

  rise of the tide
• there are two high and two low waters each tidal day, with relatively small inequality in high and low water heights

  Semidiurnal type of tide
• single high and single low water occur each tidal day

  Diurnal type of tide
• both diurnal and semidiurnal and the tide is characterized  by a large inequality in high water heights, low water heights, or in both

  Mixed type of diurnal
• occur when the moon is at the point in its orbit nearest to the earth (at perigee), the lunar semidiurnal range is increased

  Perigean tides
• occur when the moon is at the point in its orbit farthest from the earth (at apogee)

  Apogean tides
• tides with higher high water and lower low water

  Spring tides
• Occur when the moon and the sun are in line and pulling together at new and full moon

  Spring tides
• tides with lower high water and higher low water

  Neap tides
• Occurs when the moon and the sun oppose each other, as at quadratures; at first quarter or last quarter

  Neap tides
• occur when the moon is at its maximum semi- monthly declination either north or south; the diurnal effect is at a maximum

  Tropic tides
• occur when the moon crosses the equator, the diurnal effect is at a minimum

  Equatorial tides
• when high and low tides occur at about the same time everyday because of the effect of the sun

  Solar tide
• occur in few estuaries, the advance of low water trough is so much retarded that the crest of the rising tide overtakes the low, and advances as a churning, foaming wall of water

  bore
• there is a slight fall in the middle of the high water period, the effect is to create a longer period of stand during high tide

  Double low water
• there is a slight rise in the middle of the low water period, the effect is to create a longer period of stand during low tide

  Double high water
• the time between consecutive transits of moon, or 24 hours and 50

  minutes on the average

  Tidal day or Lunar day
• the interval between the moon’s meridian transit and a particular phase of tide

  Lunitidal interval
• the average elapsed time between the moon’s transit and the next high water


  Establishment of the port
• the establishment of the port during new or full moon

  Vulgar establishment
• shortening of time interval between successive high waters

  Priming
• the periodic retardation in time of occurrence of high and low waters

  Lagging
• shortest cycle for a tidal cycle

  12 hours and 25 minutes for semidiurnal
• it is completed at about 24 hours and 50 minutes.


  Lunar day or tidal day
• occurs when the moon revolves around the earth with respect to the

  sun

  Synodical month or lunar month
• it is completed at about 29 ½ days

  Synodical month or lunar month
• the phase variation of the moon as it varies from new to full or full to new

  One – half of synodical month or two weeks