Hill Fog - how ?

Discussion in 'Off-Topic Discussion' started by HarryS, Dec 21, 2017.

  1. HarryS

    HarryS Eternally Optimistic Gardener

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    Went out for a bite to eat last night. Misty when we went , but coming home the fog on the top of Parbold hill was down to about 30 yards visibility. Now they did mention hill fog on the weather today. But if fog/mist is heavy , you can see it in valley bottoms , why does it stick on top of a hill :scratch: When we drove down to the bottom it was just a light mist.
     
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    • JWK

      JWK Gardener Staff Member

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      I'd like to know the answer too having driven into a thick fog 'cloud' when driving up a hill yesterday.
       
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      • Phil A

        Phil A Guest

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        There was one sat on the A35 yesterday. It's there so often there's warning signs up :hate-shocked:
         
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        • Jiffy

          Jiffy The Match is on Fire

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          Think is something to do with hot and cold air, we don't get hill fog here but we do get sea fog and rolling mist :) as we are at sea level ;)

          Copyed from the net

          Evaporation fog is caused by cold air passing over warmer water or moist land. It often causes freezing fog, or sometimes Types of frost. When some of the relatively warm water evaporates into low air layers, it warms the air causing it to rise and mix with the cooler air that has passed over the surface.
           
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            Last edited: Dec 21, 2017
          • pete

            pete Growing a bit of this and a bit of that....

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            I tend to think hill fog is actually low cloud.
            Whereas fog that forms in hollows forms by a different means, ie. cold air dropping down hillsides and creating a cold pool of air,(similar to frost hollows), which cannot then hold the same amount of moisture as the slightly warmer air higher up, so the water condenses and forms fog.
            Often river valleys contain fog on cold mornings due to the cold air collecting and the damper atmosphere.

            Of course I could be talking rubbish.:biggrin:
             
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            • noisette47

              noisette47 Total Gardener

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              Don't think you're talking rubbish at all, @pete. There are lots of hills and valleys round here and when you're driving around, you can see the low cloud from a distance, sat on a hilltop like a big fluffy cushion. Then there's the normal fog, especially in the river valleys. And the French reckon that it's always foggy or raining in the UK! Errr...:scratch:
               
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              • Sandy Ground

                Sandy Ground Total Gardener

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                Fog and cloud are basically the same things. Its just that we as humans are used to calling low clouds fog...

                As regards hill fog. Simply put, its moist air that drifts uphill, and cools as it does so. At the bottom of the hill it would have been damp (high humidity) conditions.
                 
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                • ARMANDII

                  ARMANDII Low Flying Administrator Staff Member

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                  :love30::thumbsup::snorky:
                   
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                  • noisette47

                    noisette47 Total Gardener

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                    Well, no....clouds are (usually) in the sky? When weather conditions dictate that the cloud cover is dense and relatively low, it stands to reason that the high ground of hilltops meets the low cloud. Dammit, I'll have to get some photos to confirm the thesis :)
                     
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                    • Phil A

                      Phil A Guest

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                      Thesis bigger than both of us :heehee:

                      There was a cloud that parked on a hill for 3 days and emitted sparks and hooting noises :yikes:
                       
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                      • clueless1

                        clueless1 member... yep, that's what I am:)

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                        Was it training, waiting for its opportunity to make its name?
                         
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                        • noisette47

                          noisette47 Total Gardener

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                          What are you lot on?? And could you send me some, please?:lunapic 130165696578242 5:
                           
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                          • pamsdish

                            pamsdish Total Gardener

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                            I get a lot here in Wales and I call it low cloud on top of the hills
                             
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                            • Sandy Ground

                              Sandy Ground Total Gardener

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                              Well, er...yes....Clouds, fog, mist are all different terms for visible water vapour. What this is called depends on where it is. Up in the sky, we call it clouds. Down on the ground, fog or mist. Somewhere in between, hill fog or low cloud, dependent on the height of hill or mountain.

                              One term for visible water vapour that really gets me is when the white stuff coming out of a boiling kettle is called "steam." Its not. If it was, we could not see it...:snorky:

                              @Zigs wasnt the cloud parked on the hill for three days emitting sparks and hooting noises the one in Cornwall? The one they moved to Washington? :whistle:
                               
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                              • HarryS

                                HarryS Eternally Optimistic Gardener

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                                So it seems that "hill fog" is the low level cloud Stratos . Lovely name but 'orrible stuff ! It covers everything and often is full of light drizzle.
                                Yet another problem solved by GC :blue thumb:

                                Stratus clouds
                                 
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