Good old Dartmoor. Wet, windy, cold and murky when everywhere else is sunny, right? Well yes, sometimes but we do have some great weather here as well and those days when the high moor is bathed in sunshine when the rest of the surrounding area is under cloud are simply magical.
Cloud hanging in the valley on an early morning.
When I first started walking on the moor it was like so many other young people before and since on that fantastic event, Ten Tors. Back then I didn’t pay much attention to the weather or the forecast. If it was raining then I put my coat on and if it wasn’t I was happy!
Nowadays I’m a bit different. By checking the forecast and keeping an eye on the sky you can pick the right venue for the weather and make the most out of a potentially iffy day. It’s also really satisfying predicting the weather by looking at a few clouds in the sky.
Driving up to the high Moor from the surrounding countryside you can often find yourself in completely different weather from when you left home, and Dartmoor’s height is largely responsible for this. The height causes the temperature to drop, something called the lapse rate, by about 1deg/200m for “moist” air and 1deg/100m for “dry” air.
This can mean for instance that Princetown is on average 4 degrees colder than Plymouth which is just 23km away.
It's easy to see the temperature difference between Dartmoor, Exmoor and the surrounding coast line.
The height also causes another major factor in Dartmoor’s weather, Clouds. Dartmoor (as well as Exmoor and Bodmin) sticks above everything in the South-West and when moist air is forced to rise over the moor it cools and condenses and forms clouds, and then rain. Princetown receives twice as much rain as Plymouth and is often cloud bound whilst the coast is clear.
Building Clouds in the Lake District before a cold front, time to dive in the tent before the downpour.
During the summer a lot of the rain comes from showers and thunderstorms rather than the autumnal and winter weather systems that sweep across the Atlantic. Keeping an eye on the sky can give you some good warning when one’s on the way and enough time to get that waterproof on before it does pour down.
Cumulus Clouds developing over the hills on the Tibetan Plateau, as the warm day time air is pushed up and condenses
These shower clouds start their lives as benign little fair weather clouds known as Cumulus. These are caused by the sun heating the land, therefore causing the air to rise and therefore form clouds. These little Cumulus clouds often do nothing more and disappear overnight but during the summer when it’s warm they can continue to grow into impressive towering monsters developing into the dreaded Cumulonimbus.
These large clouds produce some really heavy showers and are normally thick, dense and can have a flattened top like an anvil. During the summer months these Cumulonimbus clouds can turn into thunderstorms, with one cloud giving about thirty minutes of thunder in it’s one hour life span with storms only lasting longer when there are many such clouds together.
So if your heading to the Moor or Mountains have a look at a decent forecast (the met office is my preferred option) and keep watching the sky, as well as your map.
Links:
- Metoffice – Good mountain weather Forecasts.
- XCWeather – Nice weather station map and a visual type forecast.
- Our very own weather page and Links.
- Cloud Appreciation Society – Fantastic photos from around the world.
Pingback: Updated Website Content | Vertical Frontiers