h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

Can anyone explain what exactly is happening when you get rain but there are no clouds about?

Not sure how universal this phenomenon is, but it happens certainly in the middle and south east of England, albeit only very, very rarely.

I assume that either a) it is light clouds way up formed of ice but not thick enough to obscure the light much, b) clouds high up that rained then passed on and there's a delay in the rain reaching the ground (how long does rain take to reach the ground?) or c) high up wet air forming ice crystals but not densly enough to form clouds, or not enough uplift to form clouds.

Just idly wondering

Interesting question - I would like more information. How much rain exactly, just a few spots or a proper shower? Are you near to trees, tall buildings or in the complete open when this happens?

The few times when I have thought it was raining and looked up to blue sky have been when it was really quite windy and the rain clouds were distant, and the rain was blowing sideways from them. The reason I asked about tall buildings near you was that the actual rain cloud might be out of your line of sight. This happens frequently in Lanzarote where the clouds can hold tropical amounts of water and there is usually a very stiff breeze.

Another cause can be that drops of water blow off soaking wet trees for quite a way.

I'd be interested to hear other points of view.

light rain, I'd say, summer shower sort (well, only time we get clear skies is summer so must be! )

No tall buildings and not droplets off trees or other large objects.

Don't recall it being very windy, but then I'm only talking about ground level, could be very windy higher up so blown off course is a viable method

Or you're being peed on by someone flying overhead in a Boeing 747

Some people pay good money for that sort of thing.

Not me.

Obviously.

Ahem.

B

This happened to me when I was over in Suffolk a err while back ago at my DAds, we were out on the patio, and it 'showered' down for maybe five or so minutes, not that* hard, and no sign of clouds, no tall buildings to obscure clouds, and we were at the top of what passes for a hill in those flat fenland areas NO trees by there either and it'd not rained in days
I'd just pressumed it must be very err non dense clouds that just didn't really have enough water in it to make it appear as a cloud...

That sounds really strange. I've never experienced that sort of rain. Hmmm.

Traveller in Times playing with a high pressure cleaner
"I can always be the neigbour washing his rooftop

Or perhaps some kids using their super soakers. "

Sadly neither those explinations would work for where I was... Its a pretty detached house far enough away from the road and neighbours...

I've experienced this kind of rain too, even out in an open field with a blue sky and no clouds within sight - and always a very light summer rain. And no wind at ground level.

One other aspect of rain that has always mystified me is when you see a sharp line on a road between wet road (from rain) and dry road. An absolutely straight line right across the road and, as mentioned, sharp.

If you look at a cloud, it doesn't seem to have any straight sides, and you'd think it'd be thinner around the edges - so how can the line between wet and dry be so sharp? And why is it never stretching diagonally across the road, but always straight across?

Ictoan
>> Not sure how universal this phenomenon is, but it happens certainly in the middle and south east of England, albeit only very, very rarely.

I recommend a visit to the sub-tropical conservatory at Kew Gardens, esp on a cool/cold day... to raise the temp and humidity, they pump steam into the air (or, at least, they used to) and every so often, for just a second or three, it... ... precipitates rain!

Titania
>> An absolutely straight line right across the road and, as mentioned, sharp.

If you look at a cloud, it doesn't seem to have any straight sides, and you'd think it'd be thinner around the edges - so how can the line between wet and dry be so sharp? And why is it never stretching diagonally across the road, but always straight across?

I can think of three possible explanations:

You travel roads that are perpendicular to OR parallel with the dominant wind direction when its raining

The timing of your observations of this phenomenon have simply coincided with the 'necessary' weather patterns

Your brain, like that of most humans', is wired to count 'hits' as more important than 'misses'





http://www.mindtweaks.com/wordpress/?p=439
[quote]
While the bias often leads us to cling to false conclusions, there’s actually a good reason our brains are set up that way.

Here’s how it works:

Let’s say we were lost in the wilderness, searching for food.

By chance, we stumble across a blackberry bush, with a handful of luscious ripe berries. We eat them, then look for more bushes. The next five bushes we find don’t have any berries on them, but the sixth bush we check has enough fruit to feed us for two days.

In this situation, our survival depends on our giving more importance to the time we found the berries, than the times that we came up empty handed.
[/quote]

See also: http://www.google.com/search?hl=en&safe=off&q=confirmation+bias+hits+misses&btnG=Search