Section 7: Tides, Waves and Routeing (Challenge Questions) Flashcards
Describe the non-astronomical component of sea level.
Storm surges
Temporary rises in sea level caused by strong winds and low atmospheric pressure associated with storms or hurricanes. Storm surges can raise water levels by several meters for a few days.
With the help of a neat and labelled diagram, define the various tidal definitions such as MHWS, MLWS, MHWN, MLWN, drying height etc.
MHWS
MLWS
MHWN
MLWN
Drying Height
CD
HAT
Explain what chart datum is and what its significance is.
- Lowest astronimical tides
- Most of the charts details are measure from the CD.
Describe the four principal harmonic constituents are tabulated in the Tide Tables.
M2:
- Principal semi-diurnal constituent
- 2x per day the waves are high caused by the Moon’s gravitational pull.
S2:
- Principal semi-diurnal constituent
- 2x per day the waves are high caused by the Sun’s gravitational pull.
K1:
- Principal diurnal constituent
- 1x per day caused by the combination of the Sun’s and Moon’s declination.
O1:
- Principal diurnal constituent
- 1x per day caused by the orbit of the Moon.
With the help of a neat and labelled diagram, explain what is ‘significant wave height’.
- The average of the 1/3 of the waves in a given sea state.
- 2x the height, 3x per day.
What are the factors which affect wave height and direction?
What is meant by optimum ship routeing?
When passage planning combines weather date, ship specifications, and operational objectives to determine the safest and most efficient route.
What are the advantages of optimum ship routeing?
- Improved fuel efficiency.
- Improved safety
- Improved ETA
- Improved Emissions
What is meant by a ship’s performance with respect to weather routeing?
Ship’s speed and fuel consumption efficiency.
What are the various resources available onboard to the Master to assist in weather routeing?
