1. Basic Navigation Lecture 5 ACP32 Vol2

2. Basic Navigation By the end of this lecture you should know:  The 6 Major Air Masses

3. Major Air Masses  The Earth’s atmosphere is constantly moving as warm air rises, cold air descends and the Earth spins.  There are 6 Major Air Masses that influence British weather.

4. Major Air Masses

5.  Arctic Maritime  Originating in the very cold Arctic seas, picks up a little moisture as it travels south. Typical weather conditions are:  Summer - Very cold with frequent heavy showers.  Winter - Very cold strong north, north-easterly winds. Heavy snow showers in north.

6. Major Air Masses  Polar Continental  Originates in Siberia. In southern Britain the weather is dry as it has not crossed much water. In northern Britain the air mass has travelled over the north sea, losing heat and picking up moisture.  Summer - Warm and dry, cloud free. East coast tends to be cool and showery with coastal fog in the north.  Winter - Sleet and snow showers in the north. Cold strong east winds.

7. Major Air Masses  Tropical Continental  Originates in North Africa, warm air moves north over Europe and has little opportunity to pick up water vapour. Typical weather conditions are:  Summer only - Very hot and dry, hazy with occasional thunder storms.

8. Major Air Masses  Tropical Maritime  Originates in warm tropical oceans around the equator. Brings warm and wet air. Typical weather conditions are:  Summer - Warm south-west winds. Low stratus cloud over west coast.  Winter - Stratus cloud, hill fog and drizzle. Warm with prolonged rainfall.

9. Major Air Masses  Returning Polar Maritime  Originates in Canada as very cold, dry air. Initially it moves south, gains warmth and moisture. By the time it reaches the Britain. Typical weather conditions are:  Summer - Warm with squally showers and storms inland.  Winter - Stratus cloud. Showers in the western mountains.

10. Major Air Masses  Polar Maritime  Originates in north Canada and Greenland, crosses the Atlantic Ocean picking up water vapour before reaching Britain. Typical weather conditions are:  Summer - Cool winds, heavy showers, thunder storms in mountains  Winter - Heavy showers in west with snow in mountains. Clear skies at night in the east giving frost.

11. Major Air Masses 1 Arctic Maritime 2 Tropical Continental 3 Returning Polar Maritime 4 Tropical Maritime 5 Polar Maritime 6 Polar Continental