Anticyclones

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Anticyclones

• The calm and still ones

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Characteristics of anticyclones

• You know the routine pens and the whiteboard
• Just think opposite of depressions

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Characteristics of anticyclones

• Relatively high pressure
• On weather maps they are closed isobars with
  pressure increasing towards the centre.
• Anticyclones move slowly and remain stationary
  over an area for several days or weeks
• The air subsides (sinks). It warms which leads to
  a decrease in relative humidity lack of cloud
  dry conditions.

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Anticyclones

• Anticyclones which establish themselves over UK
  Western Europe are called blocking anticyclones
• They deflect depressions away from UK Western
  Europe
• Extreme conditions are then produced dry and
  freezing in winter and heat waves in summer.

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Anticyclones
Unlike depressions there are two distinct types
of anticyclone
There are some similarities but in other ways are
very different
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Anticyclones

• Winter
• Cold day time temps, from below 0oc to c 5oc
• Very cold night time temps frosts below 0oc
• Generally clear skies by day night

• Summer
• Hot day time temp, over 25oc
• Warm night time temps
• May not fall below 15oc
• Generally clear skies by day night

Winter
Summer
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Anticyclones

• Summer
• Hazy sunshine in some areas
• Early morning mists which disperse quickly
• Heavy dew in the mornings
• East coast has sea frets or haars (onshore winds)
• Thunder storms can occur when RH is high

• Winter
• low level cloud may linger and radiation fog may
  remain in low lying areas
• Causes high levels of air pollution in urban
  areas as pollutants are trapped by temperature
  inversion