Wednesday, June 17, 2009

Cloud formation






Nestling as we do on the west side of the Pennines (leeward to cold Siberian winds, windward to the Americas) we are well placed to see the clouds coming in from the Atlantic & piling up on the hills

Not even in my childhood absorptions with the castles in the sky did I ever take particular notice of the process, & A level meteorology was interested only in fronts but one day last week – a basically sunny day – I went out deliberately early to the bus stop up the hill just to have the opportunity of basking a while, watching the big sky up there

And then I did notice. One rather small angry dark cloud, more submarine than anything, was being overtaken by a fluffier white cumulus about 4 times its size

It was like watching a very delicate docking procedure, or a cautious mating of two multi-tentacled beings, or a kind of continental drift in reverse. You could see the edges of the two clouds reaching out, stretching & reshaping to accommodate each other. Just as the union seemed complete the smaller cloud suddenly started roiling & puffing up, turning all white & shiny

Then I realised that the back of the big cloud was suddenly active too, roiling & puffing as if the motion at the front had been transmitted to the other side

The bus came before I could see what happened next

Yesterday I went out a bit early again, keen to see how the sky was looking after the massive thunderstorms of Monday evening (one local house actually got struck by lightning)

There were more, bigger clouds, but still enough breaks for the sun to shine through. I watched two, more equally-sized, clouds go through the docking process

Again the motion at the leading edge transferred itself to the back of the overtaking cloud. But this time it was stretching out to meet the overtures of a 3rd large cloud advancing rapidly from behind, & just as the bus arrived, a chunk detached itself & was overtaken & absorbed, though not before a fair bit of its mass had simply evaporated & disappeared from view

Today, despite what the weather forecast promised, the cloud is just a low claggy undifferentiated mass of mist; you can hardly even see the hills



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