Depressions and Anticyclones – A Revision Sheet
Low Pressure, Isobars (lines joining areas of
High Pressure, isobars far apart
equal pressure) close together
Cold and Warm air masses meet and don’t mix Cool, dry air sinks creating an area of high
easily. The cold air pushes the warm air upwards pressure, and stable weather conditions for a
creating an area of unstable weather. longer period of time (days-weeks).
Anticlockwise direction. High wind speeds– the
closer together the isobars are, the higher the Clockwise, light or no wind
Strong winds, occasionally gale force, rainfall
and cloud, thunderstorms can occur over cold
Settled weather lasting for a number of days,
clear skies, no rainfall due to little chance for
air/water vapour to evaporate:
Summer – clear skies, warm temperatures, heat
Winter – clear skies, very cold due to no cloud
cover and sun is lower in the sky in winter, no
rainfall/no snow, but... frosts and fog due to air
warming at surface as it sinks.
Rainfall – can cause flooding i.e. damage to
Summer – dehydration (particularly elderly and
homes, possessions lost, businesses, transport
children) due to not drinking enough water, heat
routes cut off.
stroke, sunburn, increased sales of ice-cream
High winds – structural damage to buildings e.g.
Effects on people
etc, water shortages if no rainfall over longer
chimneys blown off roofs, transport affected by
period of time and possibly even droughts,
fallen trees, bridges such as Severn Bridge
closed affecting transport, lorries can be blown
Winter – football and other sports games called
over in very high winds.
off due to frost, elderly people and children
Snow in winter – schools closed, elderly people
slipping on ice = broken bones, more traffic
trapped in homes, transport: roads closed due to
accidents due to icy roads, hypothermia in
snow, trains cancelled, economic losses to
businesses due to people not going into work.