Weather
The weather forecast can be found in several sources. However, traditional sources such as newspapers, TV and radio are not practical when on the hill. They are either out of date too quickly or are out of reach. The best sources in an expedition situation are from specific info centres such as MetFax or the web. Phone reports are often very expensive.
Precipitation
Highland areas, such as these used by Park House Open Award Centre, often receive more precipitation than other areas in the UK.
The high land forces the clouds up and they cool in the higher altitudes, producing rainfall. The mountains of Snowdonia (where we hold our Gold expeditions) are particularly at risk from rain because the clouds pick up a lot of moisture from the Atlantic Ocean.
Wind
Wind is simply air moving from areas of high pressure to areas of low pressure. Its direction is quoted FROM where it is blowing. Speed in general increases the closer together the isobars are.
In the mountains however, 'funnelling' is a common occurrence. This is where the wind is funnelled though a valley. The isobars are therefore more concentrated and the speed of the wind increases. This is important when deciding where to pitch your tent.
Cloud
When air cools to dew point temperature, the vapour within it condenses, forming clouds. They are 4 main types:
Cirrus
Nimbus
Cumulus
Stratus
Air Masses
Air masses are large bodies of air of the same temperature and humidity. In the UK there are 6 air masses:
* 1) Polar Maritime * 2) Returning Polar Maritime * 3) Arctic Maritime * 4) Polar Continental * 5) Tropical Maritime * 6) Tropical Continental
The Blue arrows bring cold air into the UK.
The Red arrows bring warm air into the UK.
Maritime air masses bring wet weather into the UK
Continental air masses bring dry weather into the UK.
Polar maritime is the most common air mass in the UK
Air masses influence an areas visibility, winds and precipitation.
Weather fronts
A weather front is where 2 air masses meet. There are 2 types of front.
Cold Front.
Cold air replaces warm air.
Where warm air is pushed up and rises over cold air, it is forced to cool and condense. This produces rain.
Warm Front.
Warm air replaces cold air.
