Meteorology & Seamanship Flashcards

What is the Beaufort Wind Scale and what force indicates a 'near gale'?

Answer: A scale from 0-12 measuring wind speed by observable effects; Force 7 is near gale (28-33 knots)

The Beaufort Scale (Force 0-12) describes wind speeds by their observable effects on the sea and land. Force 7 (near gale) is 28-33 knots with rough seas, Force 8 is a full gale at 34-40 knots, and Force 12 is hurricane force above 64 knots.

What does a rapidly falling barometer indicate?

Answer: Approach of a deep depression with deteriorating weather — increasing winds and precipitation likely

A rapidly falling barometer (more than 6 mb in 3 hours) indicates the rapid approach of a deep depression with associated strong winds, rain, and deteriorating sea conditions. Mariners should seek shelter or prepare for severe weather.

What is a 'synoptic chart' and how is it used in marine meteorology?

Answer: A weather chart showing isobars, fronts, and pressure systems at a specific time — used to identify wind patterns, frontal systems, and forecast weather

A synoptic chart is a weather map showing the state of the atmosphere at a specific time, with isobars (lines of equal pressure), warm and cold fronts, high and low pressure centres. It allows mariners to identify current weather patterns and anticipate changes.

What does the rule 'Wind backs and increases, mariners take notice' indicate?

Answer: A backing wind (shifting anticlockwise) with rising speed indicates a depression is approaching with deteriorating conditions

In the northern hemisphere, a backing wind (shifting anticlockwise, e.g., SW to S to SE) combined with falling pressure and increasing speed indicates a deepening depression is approaching, with worsening conditions to follow.

What are the main characteristics of a warm front passage?

Answer: Gradual deterioration with lowering cloud, continuous rain, rising temperature, and backing wind followed by clearing

A warm front is preceded by high cirrus cloud, then lowering stratus cloud, steady continuous rain, and a gradual temperature rise and wind backing as the front passes. After the warm front, conditions temporarily improve in the warm sector.

What is 'sea fog' (advection fog) and when does it typically form in UK waters?

Answer: When warm moist air moves over a cooler sea surface, cooling the air below its dew point — common in spring/early summer

Sea fog (advection fog) forms when warm moist air (often from the SW) moves over a colder sea surface and is cooled below its dew point. It is most common in UK waters in spring and early summer when sea temperatures are still cold but air temperatures are rising.