Since we last met on these pages, I’ve spent a day learning about the weather with the Met Office.
I learnt how to interpret a synoptic chart. Well. I say that. What I mean is I learnt what the heck a synoptic chart is…
Nah—to be fair, the instructors were great. I learnt, at least temporarily, loads of potentially useful meteorological gubbins. I never knew, for example, that veering and backing have technical definitions: veering is the shifting of winds clockwise around the compass and backing is the opposite.
I even learnt what most of those funny black lines on the map mean. The thin black ones without the triangles or semi-circles are called troughs. They predict vicious showers, squally winds and thunder and lightning, particularly in summer when there’s more energy in the atmosphere.
Squall! Another word that I never realised had a technical definition. Whereas a gust of wind is a short, sharp increase in wind speed, a squall is a sudden increase in wind speed of at least 18mph that lasts at least a minute. When you’re out walking on the hills, squalls are those strong winds that stop as suddenly as they started and make you, leaning into the wind, fall on your face in the mud!
Other useful things I learnt:
- Never sit at the mouth of a cave to admire a lightning storm. Do sit and admire this clever map of lightning strikes around the UK.
- The closer you are to the centre of an area of low pressure, the higher chance there is that the weather forecast will be radically wrong.
- If your cloud has defined edges, it’s made of water droplets. If your cloud has fuzzy edges, it’s made of ice crystals. Your cloud is not made of water vapour, which is invisible.
- In the northern hemisphere, if you stand with your back to the wind, then the atmospheric pressure is low to your left and high to your right. This is called, mystifyingly, Buys Ballot’s Law. I have literally no idea how this is useful. I should look that up.
- In the UK, all rain begins its life as snow.
- Amazingly, there was a man called Mr Buys Ballot. Sadly, he was Dutch so it probably isn’t pronounced the amazing way.
I’m looking forward to sharing vaguely knowledgeable meteorological facts with my expedition group tomorrow. It is somehow comforting to look up at the drizzle and say, ‘What ho, chaps, looks like this nimbostratus is settling in for the long haul!’