Meteorology Flashcards

What is the typical sequence of weather associated with the passage of a depression across UK waters?

Answer: Backing wind, falling pressure, warm front (steady rain), warm sector (cloud/drizzle), cold front (heavy showers/squalls), rising pressure, veering wind, clearing skies

A typical depression brings: falling pressure and backing wind as the warm front approaches, steady rain at the warm front, mild/overcast warm sector, then heavy rain and squalls at the cold front, followed by rising pressure and veering wind.

What is an 'occluded front' and how does it affect weather at sea?

Answer: A front formed when a cold front catches up with a warm front, lifting the warm air off the surface, often producing prolonged rain and complex wind shifts

An occlusion forms when a faster-moving cold front catches the warm front, forcing warm air aloft. This produces a complex frontal zone with prolonged rainfall and unpredictable wind shifts.

How can a barograph trace help predict weather changes offshore?

Answer: By showing the trend and rate of pressure change over time, allowing the navigator to predict approaching weather systems and their intensity

A barograph continuously records atmospheric pressure. A falling trace warns of approaching low pressure (deteriorating weather), while the rate of fall indicates severity. A rapid fall suggests a deep depression.

What is a 'ridge of high pressure' and what weather does it typically bring?

Answer: An extension of high pressure between two lows, typically bringing temporary settled conditions with light winds and fair weather

A ridge is a tongue of high pressure extending between two low-pressure systems. It typically brings a temporary improvement in weather with lighter winds, fewer clouds, and reduced precipitation before the next system arrives.

In the context of offshore sailing, what is a 'secondary depression' and why is it dangerous?

Answer: A small but often intense low that develops on the trailing cold front of a parent depression, sometimes deepening rapidly and bringing unexpectedly severe weather

Secondary depressions form along the trailing cold front of a parent low. They can deepen rapidly and bring severe, localised weather that may not be well forecast, catching vessels off guard.

What does the term 'fetch' mean in relation to wave generation?

Answer: The uninterrupted distance of open water over which the wind blows, directly affecting wave height

Fetch is the uninterrupted distance of open water over which the wind has blown. The longer the fetch, the greater the wave height. Offshore areas with long fetches (e.g., Atlantic approaches) can produce very large seas.