How fast do high clouds move?

[pineteam]

Hello Everyone,


You will agree if you cross a river on a bridge and you spot a leaf floating you will see the leaf going with the flow pretty much at the same speed of the current.
But why for example when flying at FL 330 with a 120 kt crosswind 90 degrees of your track, the high level clouds like Cbs seems not to move at all?! It seems they are static and I can't understand why with such a strong wind we don't see them crossing from left to right or vice versa pretty quickly? What's the logical explanation behind it?

[Wizofoz]

Well, firstly, cirrus clouds tend to be at altitudes higher than jet streams, so you may have a 120 kt cross wind, the cloud may be in much less wind.

But note- if you are in a 120kt cross wind, you are moving sideways at 120kts- it may well be you are looking at a cloud that appears not to be moving with the wind, because YOU have a component of motion the same as it does.

[pineteam]

Hi Wizofoz,
Thanks for your reply.


But note- if you are in a 120kt cross wind, you are moving sideways at 120kts-.

Well not really since by analogy your track is like the bridge over the river. Regardless of the wind velocity, the aircraft relative to the ground keeps the exact same path if flying at at constant track. Only the nose will veer more or less towards the wind to compensate for the crosswind component.

[Wizofoz]

Hi Wizofoz,
Thanks for your reply.



Well not really since by analogy your track is like the bridge over the river. Regardless of the wind velocity, the aircraft relative to the ground keeps the exact same path if flying at at constant track. Only the nose will veer more or less towards the wind to compensate for the crosswind component.

Yes, your track is, but when flying, do you tend to perceive your surroundings relative to your track or relative to your heading?

Lets say there's a cloud exactly in front of your nose. There is an exact crosswind blowing the could at 120kts.

The cloud is going to stay directly in front of you as YOU are also drifting over the ground relative to your heading at 120kts.

Now, if the could where on your TRACK, it's relative bearing to you would shift and it would move off your track by the time you get there.

[FlightDetent]

Ditto. Just like an intruder on the windscreen: if it is only getting bigger and not moving across the view, it will be a problem. Or you could say the clouds are converging towards a point where you will be.

[Chesty Morgan]

CB move at the speed and direction of the 10,000’ wind that’s why.

[scifi]

Also Lenticular clouds formed by Wave motions do not move at all, but remain at a fixed distance to the mountain that caused them. Their back edges are rising making the condensation, and the front edge is descending into warmer air, so is disappearing. These can be at 6000 to 30000ft.
.

[ACMS]

What.............

[scifi]

Quote... 'What.........….'

Let me educate you, if you are still willing to learn. The first two paragraphs explain....

https://en.wikipedia.org/wiki/Lenticular_cloud

( If you don't know the meaning of 'paragraph' we have failed you, many years ago.)
.

[birdspeed]

Yes, CBs move along with the mid level winds 10000-20000ft. Worth knowing when you’re trying to track around them. Usually I find their drift is half the drift you’re experiencing at jet cruise levels. But I have seem them drifting in completely the opposite direction!

[underfire]

This may help...just take a deep breath and think about it....

https://cimg1.ibsrv.net/gimg/www.gmforum.com-vbulletin/668x450/lenticularlogo_dcfd8b15a42081f47eec07c8f2bdf404296621ca.jpg

https://cimg7.ibsrv.net/gimg/www.gmforum.com-vbulletin/1236x900/fa_18_going_transonic_e1441897209245_237049055f2fb61efa18582 e5ae51ac42f173b03.jpg

[Vessbot]

Hi Wizofoz,
Thanks for your reply.

Well not really since by analogy your track is like the bridge over the river. Regardless of the wind velocity, the aircraft relative to the ground keeps the exact same path if flying at at constant track. Only the nose will veer more or less towards the wind to compensate for the crosswind component.

You're walking with a crab angle nosed into where the leaves are coming from, such that they're coming at you straight onto your nose. Up in the air, there's no bridge in the sky to see a sideways motion relative to.

Think if those clouds contained liquid drops and you flew into one, would they leave water streaks sideways on the windscreen or straight down it?

[ACMS]

Again?
what?
the Aircraft flies directly into the wind balanced so yes the water drops will blow directly back!!

I don’t see the point of the whole thread really.

[harrryw]

Now I am confused.
The OP asked about Cbs, which one good answer gave as moving with the mid level wind. CBs almost by definition have anvils. These are where the water change to ice and the rate of uplift will change letting them point to the downwind side..
At FL330 there would be little if any water to leave streaks on the windscreen.
The topic changed to Cirrus which is all upper level so the movement is primarily controlled by the wind at its level so not the same as CBs which have a resultantvelocity related to the velocity of the uplink and the wind direction at that level.
Lenticular clouds are beautiful, but not the only ones that do not move. Think of the Land of the Long White Cloud as New Zealand is sometimes known, again caused by uplift over mountain ranges.

ACMS is trying to simplify too much maybe but it may help to keep the cases seperate.

Disclaimer,,,,any Meteorology I learnt was 50 years ago so maybe clouds have changed.

[ACMS]

Ok let me try to answer the original question.

1/ CB’s grow because of rapidly rising warm air containing the large visible water droplets in the developing and mature stages. They are like little mountains and will block or resist the wind. Now as someone said above the CB will generally move in the direction of the 10,000’ wind.

How much the CB moves downwind depends on the size of the CB, ( ie the strength of the verticle currents in the developing and mature stages ) and the strength of the upper winds. In the CB dying phase the verticle uplift has stopped and the anvil cloud then blows easily with the upper wind, up to many many miles downwind in some cases.

Yes the CB is indeed moving along but because you are zipping by at up to 500 kts you don’t have time to see it, now if you flew past at 100 kts you’d probably see the movement. Look at any Met site Radar and you’ll see that a CB will generally move along.
It also depends on the geographic location of the storms, are they frontal CB’s or Tropical heat CB’s. Frontal CB’s move along quite quickly but Heat ones not so quickly .

I’ve seen many strong CB’s resist the wind so much they themselves have a little Lenticular cloud on top, just like that mountain in the photo above, it looks beautiful as you pass by.

2/ All the other high level clouds, such as Cirrus, will move with the wind at their level.
So if you are doing 500kts TAS with a 100 kt direct headwind just above a layer of Cirrus the cloud will be passing you at 500 kts and the Cloud itself doing 100 kts over the ground, you’ll be doing 400 kts over the ground.

Anything else is perception, oh and different wind at different levels!!

ok.

[dook]

I don’t see the point of the whole thread really.

Nor do I, except for a barrel of laughs.

[pineteam]

Nor do I, except for a barrel of laughs.

What's wrong of beeing curious? Your post is actually useless. xD
Plus I realise that most people don’t really have a clue. Thus my question.
Anyway thanks for the guys who actually tried to explain. It makes a little bit more sense.




the Aircraft flies directly into the wind balanced so yes the water drops will blow directly back.


The nose is at most 20/25 degrees into the wind with a 120kt crosswind. So I undestand what’s you say but I was expected to see more clouds movements. When you cross a river on a boat with a speed of 25kt at 90 degrees with a strong current, if you spot a bottle of water floating around upstream 200 meters ahead of you left of your track you will definitely see the bottle crossing your path from left to right assuming the current is from the left. Thus my initial question. Now it’s more clear after reading your post and others inputs. Thanks.

[Ian W]

Clouds very often do not move with the ambient wind it really depends how they have formed. Some of them like orographic clouds by definition just sit stationary on the hills/mountains that have caused them, exactly like ripples in a fast moving stream caused by a rock on the bottom the ripple may be stationary but the stream water is flowing fast. Just like the ripple in the stream there may be a series downstream of an orographic cloud and if the condensation level is right you can get a series of lenticular clouds that are stationary but are actually formed by the moving air stream.
Cb are normally initiated by a source of 'uplift' in humid unstable air. That uplift can be from a cold front, a hill/mountain, a source of hot warm humid air, or even two colliding winds - for example the sea breezes from East and West coasts in Florida. Cells in Cb do not last that long like a slow lava lamp so what seems to be a stationary Cb may actually be a series of cells building one after the other in the close to the same place. If the air remains unstable (look at wet and dry adiabatic lapse rates if you are interested) then the convection in the storm can be extreme and push right up to and through the tropopause. Hail can be carried up in the storms to considerable heights and at significant speed and be 'thrown' from the storms and reach as far as 20nm from the cloud. However, a strong horizontal windshear interferes with the vertical convective currents and chops the top off the storm.
In the Intertropical Convergence Zone (ITCZ) storms caused by the hot sea which provide a lot of water vapor to drive convection can reach to 70,000ft not the kind of storm to fly through.
Interesting beasts - but do not assume that they will blow along with the wind - very often they don't.