What factor determines which direction the clouds move?
Mainly wind determines the direction of cloud movement.In different layers of the atmosphere,winds blow in different directions.Clouds are carried away by the prevailing winds at the cloud level.If the vertical growth of the cloud is more,somtimes,the base of the cloud will be moving in one direction and the top of the cloud in another direction.In such cases the cloud may get disiipated. In large scale wind circulations such as Hadley cell,the coriolis force ( a force produced due to the rotation of the earth)comes into play and deflects the wind to the right side in the Northern hemisphere. The tropical storms rotate in anti-clockwise direction in the Northern Hemisphere and this whirling motion is caused by the coriolis force and the clouds associated with this storm also move in an anti-clockwise direction.