Winds on the mountains are stronger than at ground level



The wind on the hilltops tends to be stronger than an ground level, and you should allow for this when planning your walk.

Stronger Winds

The reason for stronger winds on the hills is simple when you think about it. Imagine a block of air - in the form of wind - travelling across flat-ish land. The air at that time is travelling at, say, 20mph, and it occupies a certain amount of vertical space. As that block of air hits the bottom of a mountain, the vertical space available to it is restricted, meaning that the air at the bottom of that block is forced upwards. As more and more of the block of air hits the mountain slope, more air is forced upwards, thus increasing wind speed, with the strongest being at the point where the accumulation of fast moving air passes over the mountain. Wind speed at the top of a mountain can be two to three times greater than the valley, i.e. two to three times the wind speed quoted on lowland weather forecasts, e.g. the BBC.

A 30 mph wind will be difficult to walk in, with progress being slow and more energy required. In a 40mph wind, you could be thrown off balance and normal walking will become extremely difficult.

Vulnerable Areas

Mountain summits, ridges & cols/belachs tend to have strong winds, as it's here that the fast rising air is funnelled.

There are a few places in the country that have names associated with the wind. A famous one in the Lakes is Windy Gap, which is between Great Gable & Green Gable. It's a classic col that has an open westerly aspect, which is generally where the wind comes from.

Windy Gap

An example of an area prone to strong winds is Windy Gap in the Lake District. Wind is funnelled from the west along the Ennerdale Valley, between Pillar/Kirk Fell and the High Stile Range, rising from about 150m at the valley floor to about 750m at Windy Gap between Great Gable (899m), and Green Gable (801m). 

Image courtesy of Ordnance Survey


Here's Windy Gap in reality (a little tongue in cheek from the 'actor'!)

Windy Gap is an appropriately named place, and many other similar places exist. There are no particular dangers at that location, but it is a good place to describe and understand how and why mountains have stronger winds than valleys.

Mountain Ridges

Mountain ridges are exposed and should be avoided in strong winds. More here.

Wind Speed
Always check the weather forecast for wind speeds, and at least double for the mountain tops. Learning to interpret contours will help you to anticipate the places where funnelling may be more extreme.

A few people carry anemometers (used to measure wind speed), which may seem un-necessary on the face of it. However, if you measure the wind speed and combine that information with how comfortable you felt in that wind, you can gain invaluable experience for future reference, which can feed into your route planning.

An anemometer

Take a read of @PeakRambler's blog. He's a fan of anemometers. Picture with kind permission of Peak Rambler.