Source: http://www.weatheronline.co.uk/reports/wxfacts/Air-masses-and-their-sources.htm
The United Kingdom, including Cambridge, is affected by five air masses: mT, cT, mP, cP, and A. In addition, it is affected by what is called Returning mP which is polar air that has moved south over the ocean and then returned northward to approach the U.K. from the south.
The Tropical Continental air mass originates in North Africa and approaches the U.K. from the southeast. This air tends to be dry and brings hot temperatures accompanied by clear skies in the summer. Sometimes, the air picks up moisture as it travels over the Mediterranean Sea and can result in thunderstorms.
The Tropical Maritime air mass originates in the subtropical Atlantic Ocean and approaches the U.K. from the southwest. While the air cools on its journey over the ocean, it loses little moisture. Thus, when it reaches the U.K. it brings warm, wet and overcast weather. In the summer, the clouds over Cambridge often burn off and the result is warmer and drier weather.
The Maritime Polar air originates over the Canadian arctic or the Greenland region and reaches the British Isles from the west or northwest. As the cold air mass travels over the ocean, it warms up from below and becomes unstable. Thus, the polar maritime air brings cool, moist air accompanied by rain and showers. Because Cambridge is sheltered by the Scottish and Welsh mountains, however, it remains drier than the rest of the island. In the spring and summer, the clouds heat up during the day. This results in showers and thunderstorms that can occur anywhere, including Cambridge. In winter, the showers are generally limited to the west coast.
The Arctic air mass generally only affects the U.K. in winter and is colder and drier than the Maritime Polar air. As it moves toward the British Isles, it accumulates enough moisture to generate sleet and snow. Cambridge is far enough south that it is usually not impacted by these showers and instead experiences cold weather with clear skies.
The Polar Continental air originates in Scandinavia or Russia and approaches the U.K. from the east or northeast. These air masses usually only affect the island during winter. This air causes below average temperatures in winter and above average temperatures in summer. The air is generally dry, resulting in fine and sunny weather. If the air mass passes over the North Sea between Denmark and Scotland, it gathers more moisture and brings cloudy weather to Cambridge, sometimes accompanied by drizzle or light snow.
Forecast for April 5, 2012 - April 8, 2012:
Source: http://www.metoffice.gov.uk/weather/uk/uk_forecast_pressure.html
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Cold front
The leading edge of an advancing colder air mass. Its passage is usually marked by cloud and precipitation, followed by a drop in temperature and/or humidity.
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Warm front
The leading edge of an advancing warmer air mass, the passage of which commonly brings cloud and precipitation followed by increasing temperature and/or humidity.
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Occluded front (or 'occlusion')
Occlusions form when the cold front of a depression catches up with the warm front, lifting the warm air between the fronts into a narrow wedge above the surface. Occluded fronts bring cloud and precipitation.
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Developing cold/warm front (frontogenesis)
Represents a front that is forming due to increase in temperature gradient at the surface.
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Weakening cold/warm front (frontolysis)
Represents a front that is losing its identity, usually due to rising pressure. Cloud and precipitation becomes increasingly fragmented.
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Source: http://www.metoffice.gov.uk/weather/uk/uk_forecast_pressure.html
Cambridge is affected by cold fronts, arm fronts, and occluded fronts. By Saturday April 7, a warm front will have passed through Cambridge from the northwest, followed by a cold front approaching from the northeast. That cold front will then be followed by another warm front coming from the northwest by Sunday April 8. For Friday April 6 and Saturday April 7, Cambridge is expecting cloudy skies with relatively good visibility. By Sunday, however, there will be showers brought on by the arrival of the second warm front.
Cambridge lies in the eastern plains of England on the lee side of the Scottish and Welsh mountains. Since the maritime air masses approach the U.K. from the west and the continental air masses approach the U.K. from the east, Cambridge is typically drier than the majority of the island. The wetter air of the maritime air masses must pass over the mountains before reaching Cambridge, causing a slight rain shadow effect, while the drier air of the continental air masses approaches Cambridge directly. In general, Cambridge doesn't experience severe weather such as hurricanes or tornadoes. Instead, the weather remains fairly consistent throughout the year.
Cambridge lies in the eastern plains of England on the lee side of the Scottish and Welsh mountains. Since the maritime air masses approach the U.K. from the west and the continental air masses approach the U.K. from the east, Cambridge is typically drier than the majority of the island. The wetter air of the maritime air masses must pass over the mountains before reaching Cambridge, causing a slight rain shadow effect, while the drier air of the continental air masses approaches Cambridge directly. In general, Cambridge doesn't experience severe weather such as hurricanes or tornadoes. Instead, the weather remains fairly consistent throughout the year.
References:
http://www.metlink.org/weather-climate-resources-teachers/key-stages-weather-climate/key-stage-4-weather/ks4-airmasses-2.html
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