Meteorology and Environmental Factors Flashcards
7 cards from real VTS practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Meteorology and Environmental Factors flashcards as text
What hydrodynamic phenomenon causes a vessel to sink deeper into the water when transiting shallow channels at speed, reducing available under-keel clearance?
Answer: Squat
Squat is a hydrodynamic effect where a vessel moving through shallow water experiences reduced pressure under the hull, causing it to settle lower and potentially reducing under-keel clearance to dangerous levels.
A temperature inversion exists over the harbor. How does this atmospheric condition most likely affect VHF radio communications used by VTS?
Answer: It can cause ducting, extending VHF range well beyond normal line-of-sight limits
A temperature inversion creates a boundary layer where warmer air overlies cooler air, which can trap and refract VHF radio waves, causing 'ducting' that extends usable range far beyond normal line-of-sight.
What is 'significant wave height' as reported in marine weather forecasts provided to VTS operators?
Answer: The average height of the highest one-third of all waves in a given period
Significant wave height is the average of the highest one-third of all waves in a measurement period, and it closely corresponds to what a trained mariner would visually estimate as the prevailing wave height.
When tidal current through a harbor entrance exceeds 4 knots, what action would a VTS operator typically recommend or require for a large inbound vessel?
Answer: Delaying vessel transit until the current decreases to a manageable level
Strong tidal currents severely reduce a vessel's maneuverability and steering response; VTS operators advise delaying transit until the current slackens, as timing a passage around slack water is standard maritime practice.
What is a 'storm surge' and why must VTS operators account for it in their traffic management decisions?
Answer: A wind-driven and low-pressure-induced rise in sea level that affects actual water depths and port flooding risk
A storm surge is an abnormal rise in sea level caused by strong onshore winds and low atmospheric pressure; it changes actual under-keel clearances, can cause dock flooding, and affects the safety of vessels already moored.
How should a VTS operator adjust traffic management when a dense fog advisory is in effect across the port service area?
Answer: Implement reduced speed advisories and increase minimum separation distances between vessels
In restricted visibility, VTS implements enhanced traffic management including reduced speed advisories and increased vessel separation to provide additional stopping distance and reaction time, reducing collision risk.
What is 'ice accretion' and what specific navigation hazard does it present to vessels monitored by VTS in winter conditions?
Answer: Build-up of ice on the vessel's superstructure causing stability loss due to increased topside weight
Ice accretion on superstructure, decks, and rigging adds significant weight high above the waterline, raising the vessel's center of gravity and reducing metacentric height, which can lead to capsizing.