The natural Navigation: The Right Course, Naturally

A blog of two halves for you today.

Late September can bring some of the best early evening experiences for those who enjoy looking upwards.

Visibility is likely to fluctuate a bit, but it looks as though we may get some of the best stargazing weather of the year over the next few nights. It promises to be warm enough to enjoy long spells outside, but without the crazily late sunsets of midsummer.

I’ll point out a few of the things worth looking for in a minute, but first just a few words about this weather.

On my courses I encourage people to take note of shifts in wind direction and how this relates to changes in weather patterns. If the weather is unseasonably warm or cold, we should expect some deviation from the prevailing wind direction, southwest.

The image above shows the UK (at lunchtime tomorrow) sandwiched neatly between…

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My thanks to Richard Webber for sending in this photo. The telegraph poles in this picture are leaning from the southwest to the northeast. This is in line with the prevailing wind, which is easy to tell in the photo if you look at the straggly bits that have been combed over at the top of the hedge.

The question is, is this a coincidence or the cause?

Please could anyone pass on any observations they have of leaning telegraph poles and together we may be able to forge a new technique.

One of the first things that Charles Darwin discovered, during his epic travels on board the Beagle, was a dramatic natural navigation clue. Darwin was exploring the island of Santiago in the Cape Verde Islands, as he recounts in ‘The Voyage of the Beagle‘,

‘Another day we rode to the village of St. Domingo, situated near the centre of the island. On a small plain which we crossed, a few stunted acacias were growing; their tops had been bent by the steady trade-wind, in a singular manner – some of them even at right angles to their trunks. The direction of the branches was exactly north-east by north, and south-west by south, and these natural vanes must indicate the prevailing direction of the force of the trade-wind.’

Darwin uses the acacias to deduce the direction of the trade-winds in this instance, rather than find direction, but having established this…

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The recent cold snap brought by northerly winds left the first frost across the south of England. The southern side of this chimney was sheltered from the wind and this is how it may have escaped a frost. It certainly had nothing to do with any heat from the chimney, no fire had been lit in it for the week before.

The other possibility is a gap in the roof’s insulation allowing more heat from the home to escape. Judging from the second frost-free patch on the right, it looks like it might be time to crawl around in the attic. Unfortunately we are battling with cluster flies up there at the moment so it is not a fun place to be. Must be a wind shadow in both cases. Definitely.

The northerly winds were carrying high cirrus and contrails down towards the coast this morning. They have brought colder air, as forecast yesterday. This gave us our first frost of the season. The feel and even the sounds of the grass underfoot have a relationship with the direction the air is moving.

I was in Brighton yesterday afternoon and the coast was being hit hard by a southerly gale. When the wind is this strong it is interesting feeling how its direction twists and turns round the streets of a town like Brighton. It never turns a full 180 degrees, but regularly gusts out from alleyways at right angles to the main wind. The smudge in the sky in the top left of the photo is a flock of birds.

The wind brings with it the character of the land, or water, it passes over. It adopts signature scents and temperatures and if the land of an area is known well enough, it is often possible to deduce the direction that a wind is coming from by analysing its character. Gustave Flaubert does a humorous and divine job of exposing this concept through the mouth of the young chemist in his novel, Madame Bovary:

‘And, as it happens, we are sheltered from the north wind by the Forest of Argueil on one side, from the west wind by the Cote Saint-Jean on the other; and this heat, you see, which on account of the water vapour given off by the river and the considerable presence of cattle in the meadows, which exhale, as you know, a good deal of ammonia, that’s to say nitrogen, hydrogen and oxygen (no, just…

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During a short outdoor navigation course yesterday, nature once again enjoyed mocking me a little.

While discussing methods of using the wind to navigate, I had explained how wind direction is surprisingly constant over a period of hours and although small shifts are common, large changes are much less so, and complete reversals very rare. The key is understanding that a significant change in wind direction will be caused by a change in the relationship between your location and a nearby weather system, ie. a front moving through. The change in weather is usually gradual enough to foretell of wind shifts, but not always…

Yesterday we witnessed a complete flip, the wind direction shifted almost 180 degrees from south-southwest to north in one hour. This was something that I had just proclaimed to be almost unheard of, unless there was a complete change in weather. The weather had not yet…

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