RENDLESHAM WEATHER STATION | FREE LEARNING CENTRE

Volume 2: Weather Fronts and Pressure Systems

Lesson 2.1: High and low pressure

Atmospheric pressure is the weight of air above a place. Sea-level pressure is often

expressed in hectopascals (hPa); standard sea-level pressure is about 1013 hPa. High

pressure often brings settled conditions, but can also trap winter fog. Low pressure

often accompanies cloud, rain and wind. Neither guarantees a particular outcome.

Try it: Record pressure at the same time on three consecutive days.

Quick quiz: Does high pressure always mean sunshine?

Answer: No.

Lesson 2.2: Warm and cold fronts

A front separates air masses with different characteristics. A warm front often brings

increasing layered cloud and prolonged rain as warm air rises over cooler air. A cold

front can bring a narrower band of rain or showers as colder air advances. Actual

weather varies greatly.

Try it: Find a Met Office synoptic chart and locate a front near the UK.

Quick quiz: What does a cold front mark?

Answer: The leading boundary of advancing colder air.

Lesson 2.3: Occlusions and Atlantic depressions

An occluded front forms when a cold front catches up with a warm front in a

developing low-pressure system. Atlantic depressions frequently affect Britain, and

their tracks determine the timing of rain and strong winds. Isobars show equal

pressure; tightly packed isobars often indicate stronger winds.

Try it: On a weather chart, compare isobar spacing over two regions.

Quick quiz: What do closely spaced isobars commonly indicate?

Answer: A stronger pressure gradient and potentially stronger winds.

Talk about it: What did you learn, and how might it help you understand the weather Where you live?