VTS Meteorology and Environmental Factors 3

Question 1

What tidal data does a VTS operator use to calculate a deep-draft vessel's available under-keel clearance for a channel transit?

Accepted Answer

The predicted tidal height at the time of transit added to the charted depth above chart datum

Answer

Only the predicted high tide height for that date

Answer

Mean sea level measurements averaged from the previous week

Answer

The arithmetic average of the predicted high and low tide heights

Question 2

What does 'wind shear' describe in the context of vessel maneuvering in a port approach that VTS operators must communicate to inbound traffic?

Accepted Answer

A rapid change in wind speed or direction over a short horizontal distance or height

Answer

The lateral force exerted by a steady beam wind on a vessel's hull area

Answer

The interaction between opposing tidal current and headwind in a channel

Answer

Turbulent airflow behind port structures that degrades radar returns

Question 3

How does a 'vessel traffic image' (VTI) maintained by VTS become less accurate during heavy precipitation?

Accepted Answer

Radar sea clutter and rain clutter obscure or create false targets, degrading the composite traffic picture

Answer

AIS transponders shut down automatically in rain, removing targets from the display

Answer

DGPS accuracy degrades in rain, causing position errors in AIS reports

Answer

Shore-based CCTV cameras used to supplement the VTI become blocked by rain

Question 4

During a strong offshore wind event, what specific maneuvering hazard should a VTS operator warn an inbound vessel about when approaching the berth?

Accepted Answer

Wind-driven lateral set pushing the vessel toward the lee side of the channel or dock structures

Answer

Increased propeller cavitation due to turbulent following seas

Answer

Temporary reduction in radar detection range for small craft ahead

Answer

GPS signal degradation caused by atmospheric scintillation effects

Question 5

What is the Coriolis effect's primary influence on large-scale low-pressure weather systems that VTS operators should understand when interpreting marine forecasts?

Accepted Answer

In the Northern Hemisphere it deflects winds to the right, producing counterclockwise circulation around low-pressure centers

Answer

It causes winds to blow directly and without deflection from high pressure to low pressure

Answer

It causes sea surface temperatures to rise rapidly during storm passage over warm water

Answer

It generates predictable tidal currents in estuaries and tidal rivers

Question 6

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?

Accepted Answer

Log the advisory, broadcast it on the working channel, and advise vessels of current conditions

Answer

Immediately close the port to all vessel traffic regardless of vessel size

Answer

Redirect all inbound vessels to the nearest designated safe anchorage

Answer

Transfer watch authority to the Coast Guard Sector Commander

Question 7

What is the significance of 'sea clutter' on a VTS radar display during periods of high wind and wave activity?

Accepted Answer

Sea clutter consists of radar returns from wave surfaces that can mask small vessel targets near the antenna

Answer

Sea clutter enhances detection of low-lying obstacles such as navigation buoys

Answer

Sea clutter only appears on older analog radar systems, not modern ARPA displays

Answer

Sea clutter indicates the presence of a strong temperature inversion causing ducting