Source is over the North Atlantic, this air is damp and cool - Around 10 degrees (c)
n summer this airmass is associated with cool, showery weather with bright, clear conditions in between.
In winter, the air still brings cool (slightly cooler 5c) and showery conditions to Britain with some warm intervals.
The weather is pretty much the same, but the temperature is lower.
Source is over Siberia/Eastern Europe. Unlike the polar maritime air mass, this brings different weather depending on the season.
- In summer, land heats up quickly as the air has a summer temperature of around 20c.
Due to the lack of moisture, this air is usually dry and easterly winds in summer tend to bring dry,warm, sunny weather.
- The rapid cooling of the continental land surface in winter leads to the build up of cold (-10c), dense air over Central and Eastern Europe. Although the air is dry it can absorb high levels of moisture over the North Sea.
This occured this year, when we had a very cold march/april.
This air mass has a source under the semi-permenant Azores high pressure region.
- Due to the Tropical Maritime air mass being warm (22c) and moist. The resulting weather is layered clouds that produce dull, drizzly overcast weather in summer. This cloud in-tern reduces the temperature.
- This air mass brings mild and damp conditions in winter. With its source temperatures of around 18c, the air is still relatively warm by the time it reaches us.
This air mass has a source region in Northern Africa and - although relatively uncommon.
In summer, it produces very hot (30c), dry conditions. This usually ends with a thunderstorm as the moist Tropical Maritime air starts to advance again.
In winter, this air mass is even rarer and the weather associated are very unusual and bring mild conditions with warm, sunny spring-like weather for a few days.