RYA Yachtmaster Advanced Meteorology — Questions and Answers
Question 1: A 'trough of low pressure' on a synoptic chart (weather map) is characterised by:
- A line of closely packed isobars extending from a low centre — often associated with wind shifts, squalls, and deteriorating weather (Correct answer)
- A region of high pressure
- An area of stable, settled weather
- A wind direction change from west to east
Correct answer: A line of closely packed isobars extending from a low centre — often associated with wind shifts, squalls, and deteriorating weather
A trough is an elongated extension of low pressure. Isobars are closely packed and kinked. Troughs are associated with instability, gusty winds, showers, and sharp wind shifts.
Question 2: The Buys Ballot Law states that in the Northern Hemisphere:
- If you stand with the wind on your back, low pressure is to your left (port) (Correct answer)
- High pressure is always to the north
- Wind always blows from south to north
- If you face the wind, low is to the right
Correct answer: If you stand with the wind on your back, low pressure is to your left (port)
Buys Ballot's Law: in the Northern Hemisphere, face the wind and low pressure is to your right (actually: stand with wind at your back, low is to your LEFT). Geostrophic wind blows parallel to isobars, anti-clockwise around lows.
Question 3: A veering wind in the Northern Hemisphere (shifting clockwise, e.g., SW to W to NW) typically indicates:
- A cold front has passed — improving weather behind it (Correct answer)
- A warm front is approaching
- Fog is developing
- A tropical cyclone is nearby
Correct answer: A cold front has passed — improving weather behind it
In the Northern Hemisphere, a clockwise (veering) wind shift — especially SW→NW — is the classic post-cold-front signature: pressure rising, temperature falling, visibility improving (though showers may follow).
Question 4: What is 'radiation fog', and when is it most likely to affect an offshore passage?
- Fog that forms over land overnight as land cools radiatively, and drifts offshore in the morning with the land breeze — most likely in light wind, clear-sky anticyclonic conditions (Correct answer)
- Fog caused by nuclear radiation
- Fog associated with warm fronts only
- Fog that forms only in winter
Correct answer: Fog that forms over land overnight as land cools radiatively, and drifts offshore in the morning with the land breeze — most likely in light wind, clear-sky anticyclonic conditions
Radiation fog forms overnight as land surfaces radiate heat. In light anticyclonic conditions, it can drift offshore. Sea fog (advection fog) — a separate type — forms when warm moist air flows over cold water.
Question 5: For a cross-Channel passage, which Met Office forecast service provides the most detail for skipper-level planning?
- Inshore Waters Forecast combined with the 5-day shipping forecast text and synoptic chart — plus GRIB files for wind modelling (Correct answer)
- BBC Radio 4 forecast alone
- A smartphone app without verified meteorological data
- VHF Channel 16 only
Correct answer: Inshore Waters Forecast combined with the 5-day shipping forecast text and synoptic chart — plus GRIB files for wind modelling
Skilled passage planning uses multiple sources: Inshore Waters Forecast (detailed coastal), Shipping Forecast (overview), synoptic charts, and GRIB numerical model data for wind and wave forecasts.
Question 6: A 'secondary depression' forming on a cold front can be particularly hazardous because:
- It may intensify rapidly and is often not forecast as accurately as the primary low, causing unexpected severe conditions (Correct answer)
- It brings clear skies and no wind
- It only affects the Eastern Channel
- It always tracks south of the English Channel
Correct answer: It may intensify rapidly and is often not forecast as accurately as the primary low, causing unexpected severe conditions
Secondary depressions forming on the trailing cold front of a primary low can deepen rapidly (sometimes 'bomb'), bringing unexpected gales. They may not appear on early forecast charts, catching skippers unaware.
RYA Yachtmaster Advanced Meteorology
A 'trough of low pressure' on a synoptic chart (weather map) is characterised by: