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 tidal data does a VTS operator use to calculate a deep-draft vessel's available under-keel clearance for a channel transit?
Answer: The predicted tidal height at the time of transit added to the charted depth above chart datum
Available depth equals the charted depth (referenced to chart datum) plus the predicted tidal height at the time of transit; VTS operators use this calculation to confirm whether a vessel's draft allows safe passage.
What does 'wind shear' describe in the context of vessel maneuvering in a port approach that VTS operators must communicate to inbound traffic?
Answer: A rapid change in wind speed or direction over a short horizontal distance or height
Wind shear is a rapid change in wind speed or direction across a short distance; in port approaches it can cause vessels to suddenly experience very different wind forces on different parts of the ship, complicating maneuvering.
How does a 'vessel traffic image' (VTI) maintained by VTS become less accurate during heavy precipitation?
Answer: Radar sea clutter and rain clutter obscure or create false targets, degrading the composite traffic picture
The VTI depends heavily on radar; heavy rain creates precipitation clutter that can mask real targets or generate false echoes, reducing the VTS operator's situational awareness of vessel positions.
During a strong offshore wind event, what specific maneuvering hazard should a VTS operator warn an inbound vessel about when approaching the berth?
Answer: Wind-driven lateral set pushing the vessel toward the lee side of the channel or dock structures
A strong wind acts on the vessel's above-water windage area (hull topsides, superstructure, containers), causing lateral drift toward leeward obstructions, particularly dangerous at the slow speeds used during berthing.
What is the Coriolis effect's primary influence on large-scale low-pressure weather systems that VTS operators should understand when interpreting marine forecasts?
Answer: In the Northern Hemisphere it deflects winds to the right, producing counterclockwise circulation around low-pressure centers
Earth's rotation deflects moving air to the right in the Northern Hemisphere (Coriolis effect), producing counterclockwise (cyclonic) rotation around low-pressure systems, which determines the wind pattern VTS operators expect as a depression approaches.
A VTS operator receives a NAVTEX message issuing a 'small craft advisory' with sustained winds of 25 knots. What is the VTS operator's most appropriate response?
Answer: Log the advisory, broadcast it on the working channel, and advise vessels of current conditions
The VTS information service role requires logging relevant meteorological advisories, broadcasting them to vessels in the service area, and keeping masters informed so they can exercise their own judgment regarding safe navigation.
What is the significance of 'sea clutter' on a VTS radar display during periods of high wind and wave activity?
Answer: Sea clutter consists of radar returns from wave surfaces that can mask small vessel targets near the antenna
Sea clutter is radar energy reflected back from breaking wave crests; in high sea states it appears as a bright, noisy region near the radar center that can conceal small vessel echoes, reducing the accuracy of the VTI.