Above picture Loch Sloy Dam 

WEATHER

Weather

If you have an idea what the cloud formations are it could give you an indication what the weather will be. 

Altocumulus:

Height 7,000 to 17,000 feet.

Occasionally some slight rain or snow perhaps in the form of a shower may reach the ground. On some occasions a thunder storm may occur. 

Stratocumulus:

Height 1,200 to 7,000 feet.

May produce light rain or snow. 

Cumulos:

Height 1,200 to 6000 feet.

Well developed cumulus may produce showers. 

Altostratus:

Height 8,000 to 17,000 feet.

May give light rain or ice pellets. 

Stratus:

Height 1,200 to 7,000 feet.

May produce drizzle or snow grains. 

Cumulonimbus:

Height 1,000 to 5,000 feet.

Accompanied by heavy showers, perhaps with hail and thunder. 

Cirricumulus:

Height 17,000 to 35,000.

Composed of ice crystals. 

Cirrus:

Height 17,000 to 35,000

Composed of ice crystals. 

Nimbostratus:

Height 1,500 to 10,000 feet.

Accompanied by moderate, or heavy rain or snow, occasionally ice pellets. 

Cirrostratus:

Height 17,000 to 35,000 feet.

Composed of ice crystals.  If cloud is thin either the sun or moon will have an halo around it. 

Cloud Formation Due To Weather Fronts.

Cold air is more dense tha warm air, so when a warm mass meets  a cold air mass, the cold air ends up below the warm air. Once the air has risen, it cools and clouds can develop. 

A cold front is where a cold air mass is pushing into a warm air mass. Cold fronts can produce dramatic changes in the weather. They move fast, faster than a warm front.

Normally, when a cold front is passing winds become more strong and there is a drop in temperature, and heavy rain can occurr, also sometimes with hail, thunder and lightning. Lifted warm air ahead of the front produces cumulus or cumulonimbus clouds and thunderstorms. Atmospheric pressure changes from falling to rising at the front. After a cold front moves through the temperature will be cooler, rain stops and the cumulos clouds are replaced by stratus and stratocumulus clouds, or even clear skies. 

Beaufort Wind Scale.pdf Beaufort Wind Scale.pdf
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Type : pdf

How to tell if the weather is going to get worse

  • If more cloud is forming, especially at the medium or low levels, or the cloud that is present is getting thicker and blacker.
  • Clouds that are racing across the sky begin to get fuller and blacker.
  • Clouds are moving in all directions.  This indicates extreme instability.
  • If it is a hot day and the clouds begin to grow in the early mid morning, there is a good chance of rain possibly thunders later in the evening.
  • The cloud begins to drop. 

How to tell if the weather will get better

  • Fog disappears and is replaced by clear skies by midmorning, or early afternoon.
  • The cloud base is obviously rising, and possibly holes begin to appear in the covering.
  • If any of the cirrus style clouds do not change but stay thin and wispy, then it would be a fair assumption that it will stay dry.

Thunder and Lightning

If you get caught out in a storm you should think about the following:

  • Avoid any high ground, you do not want to be the tallest thing in the area.
  • Be aware of metal objects like walking poles, ice axes put them down if safe to do so.
  • Keep away from all objects like trees, pylons or any tall feature, avoid water. And keep away from fences.
  • If you are in a group spread out, lightning can jump from one person to another.
  • Find the lowest bit of ground and sit on your backpack, make sure you bring your knees up to your chest, and do not lie down  

Wind Direction

Is generally the same at sea level as it is on the summit. However, on the way up there will be many local anomalies in the corries and the gaps and in the valleys that will affect the wind. Wind can swirl, rotate and bounce off in response to the mountains around. The wind can become unpredictable and dangerous depending on the wind speed.

Wind Speed

This doubles from sea to Munro height. Don't get caught out by this. It may have been a general breeze of 10 to 15 mph in the car park will increase towards the summit.  Higher winds 35 mph plus will become gusty and dangerous.

Rain

If in general the wind in the UK comes across a large expanse of water like the Atlantic water will be soaked up like a sponge. The air holds this water until it has a chance to cool, and the best way to cool the air is to push it upwards. Mountains are very good at this. As the air goes up. it reaches a point where the water condensates (dew point) and forms cloud (hill mist). Pushed up higher then you will get drizzle, rain, hail and snow depending on temperature and the height. The hills in Scotland are famous for often getting snow in summer because of this.

Temperature

Will get colder as you go higher; in the UK -1deg Centigrade for every 150 metres of ascent is the average. However the real killer in the hills is wind chill.  If it is at all breezy then the temperature will feel a lot colder. And if you are wet then you are in danger of exposure and not protected from the wind. It only needs to be blowing at 15 mph to take several degrees of the actual temperature

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