UKC

doing ML(s) and cant get my head around the weather. It is baffling! So here is my conundrum...
Low pressure is moist warm air rising.
High pressure is cold dry air sinking.
So why is high pressure associated with warm settled weather if it is cold air?

I might be having a brain fart but I cant figure it out. Or should i just accept it is one those "that's just how it is" things ? Can someone please explain?

In reply to stucknortherner:

Hmm where do we start!!
So Warm air can hold more moisture vapor in suspension than cold air. FACT!
As air rises it cools (hence its colder on the top of the hill)
As the rising are cools, the moisture vapor condenses out to form CLOUDS, if enough condenses out it RAINS
Conversely, high pressure air is descending from high up in the atmosphere, so its already COLD, therefore a lot of the water vapor has already condensed out. As it descends it warms up and therefore can hold even more moisture vapor in suspension than before. So, Little or NO CLOUD = No rain!
No cloud cover allows more sun to penetrate to the top of your head, so although the air may have started colder, it can fell very hot!!

Hope that helps! lots of resources of the met office site, see if I can find a link

M

In reply to stucknortherner:

Think of it like a vacuum cleaner and a leaf blower.

Low pressure = Vacuum cleaner, sucks all the crap in.

High pressure = Leaf Blower, pushes all the crap away.

Also as warm moist air rises it cools, reaching the dew point. Water vapour condenses into droplets. Clouds form and it rains. (Low pressure)

Drier air sinking (and warming up as it does) allows for more water vapour to be held in the air and the temperature gets further from dew point so clouds evaporate. (High pressure)

So as there are fewer clouds, the weather is usually clearer during high pressure spells. Also the high pressure areas tend to be a little more stable and can "block" low pressure systems.

Blocking high pressure areas are particularly welcomed by winter climbers as they often mean sustained spells of clear weather which allows the night time temperatures to drop well below freezing.

Overly simplistic but might help.