1. Basic Navigation
Lecture 6
ACP32 Vol2

2. Basic Navigation By the end of this lecture you should understand:
Weather
Fronts
Cloud Types

3. Weather
Much of the weather in Britain is caused by massive areas of air at differing pressures.
To visualise pressure
areas on a chart or map
meteorologists join
areas of the same
pressure together in
a line, an ISOBAR.

4. Weather Think of Isobars as contour lines on a map.
Steep/concentrated Isobars indicate high winds.
Shallow, spaced out Isobars indicate slower moving air.
Areas of LOW pressure, depressions, bring unsettled weather.
Areas of HIGH pressure, anti-cyclones, bring calm weather.

5. Fronts When masses of cold air and warm air meet a FRONT occurs.
The COLD air/front will bring poor weather.
The WARM air/front will bring stable weather.

6. COLD and WARM air meet and the warm rises.
Fronts
COLD and WARM air meet and the warm rises.

7. As the WARM air rises the cold rushes underneath and begins a spin.
Fronts
As the WARM air rises the cold rushes underneath and begins a spin.

8. Fronts
WARM air is trapped above the cold, spinning stops and the front dissipates. This is now known as an OCCLUDED Front

9. Fronts
In an OCCLUDED Front both the WARM and COLD air are present in the same space

10. Fronts Similar to a front is an Anticyclone
This is a mass of high pressure air creating light winds that spin clockwise (in the northern hemisphere) around the centre of high pressure.
They are stable slow moving systems, consisting of warm dry air, bringing long periods of fine clear weather.

11. Cloud Types There are 3 main types of cloud:
1 Cirrus high altitudes and composed of ice crystals. The word cirrus means a thread or hair.
2 Cumulus a lumpy or fluffy cloud.
3 Stratus a featureless layer of cloud.

12. Cloud Types
These three words can be used to describe distinct types of clouds.
The words cumulus and stratus on their own identify clouds whose base is below 2000m.
Cumulus may be combined with nimbus (Latin for rain), to give cumulonimbus - a heaped rain cloud.
A layer of cloud from which rain is falling is nimbostratus.

13. Cloud Types

14. Cloud Types