when the winds are variable why cant the low clouds move in different directions like the winds at ground ?

Answer 1

The area next to the earth's surface the winds are affected by the differential heating and frictional forces of the terrain, trees, buildings...etc. This lowest layer is referred to as the boundary layer by forecasters. The various things all influence what the wind speed and direction and the turbulence caused by the wind going over and around hills, buildings, trees, cars, ...etc causes the variable directions in very light (generally less than 10 mph) wind conditions. Once you get above the boundary level, frictional forces are very much removed and it becomes a balance between the pressure gradient (the differences between high pressure and low pressure systems) and the Coriolis force, and other lesser forces. Those winds are quite predicable and mathematical models do a very good job in forecasting those...particularly the first 48 hours of the forecast period. Most of the clouds off the earth surface are above that boundary level that is so heavily influenced by the frictional forces against the compressible gas-fluid we call air and travel in one direction while the ones at the ground level are going all over the place due to turbulence induced by the boundary level frictional forces.

The clouds will move in what ever the air flow happens to be next to the ground they will indeed move in any direction the turbulent flow takes them.

Answer 2

Winds at upper levels need not be the same as it is at ground levels.In the tropics the height of the base of low clouds may go upto 2 kms.The wind speed sometimes may be more than 20 Kmph at a height of 500 metres even though the wind is calm at the ground level.The wind direction and speed may vary for different heights.That is why balloons are released every day with sensors to know about temperature, humidity, pressure in addition to wind speed and directions at upper levels.For the first one Km,wind speed and directions are reported for every 300 metres as there are likely to be variations within that one Km.So clouds at a particular level will be moving according to the speed and direction of the wind blowing at that level.

Answer 3

Sometimes they do!
A simple example is ground fog versus low cumulus clouds at 3000 feet. These often move in different directions.