MCA CoC Meteorology at Sea 2

Question 1

What is the difference between a cold front and a warm front, and how do they affect weather conditions at sea?

Accepted Answer

A cold front is a boundary where cold air undercuts warm air causing rapid weather changes with heavy showers and squalls; a warm front is where warm air rises over cold air causing prolonged rain and gradually lowering cloud

Answer

There is no practical difference at sea

Answer

A cold front brings warm air replacing cold air; a warm front brings cold air replacing warm air

Answer

Cold fronts only occur in winter; warm fronts occur in summer

Question 2

What causes sea fog (advection fog) and in which conditions is it most commonly encountered in UK waters?

Accepted Answer

Warm, moist air moving over a colder sea surface, common in spring and early summer when sea temperatures are still low

Answer

Cooling of the sea surface at night, common in winter

Answer

Heavy rainfall reducing visibility near the sea surface

Answer

Strong winds mixing cold air downward from higher altitudes

Question 3

What is the significance of the 'diurnal variation' of barometric pressure for a mariner in tropical waters?

Accepted Answer

A regular daily oscillation of about 1-3 hPa — disruption of this pattern is an early warning of tropical cyclone approach

Answer

It indicates the strength of the tide

Answer

It measures the difference between day and night temperatures

Answer

It shows wind speed changes between day and night

Question 4

A vessel in the North Atlantic observes the wind backing from west to south-west and the barometer falling steadily. What weather system is most likely approaching?

Accepted Answer

A depression (low-pressure system) with its warm front approaching from the west

Answer

A high-pressure ridge

Answer

An anticyclone bringing settled weather

Answer

A cold front with clearing skies behind it

Question 5

What is the difference between 'wind speed' and 'gust speed' as reported in marine weather forecasts?

Accepted Answer

Wind speed is the sustained mean speed over 10 minutes; gust speed is a brief maximum lasting 3-5 seconds that can exceed the mean by 40% or more

Answer

They are the same measurement expressed in different units

Answer

Wind speed is measured at sea level; gust speed is measured at mast height

Answer

Gust speed is always exactly double the wind speed

Question 6

What are 'isobars' on a weather chart and what can a mariner deduce from their spacing?

Accepted Answer

Lines of equal pressure — closer spacing indicates stronger wind (steeper pressure gradient)

Answer

Lines of equal temperature — closer spacing means warmer conditions

Answer

Lines of equal wave height — wider spacing means calmer seas

Answer

Lines of equal humidity — closer spacing means fog is likely