A violent storm provides intense and lasting upward which gives rise to a tornado and prevents the heart at low pressure to fill the high current. When the top is observed a storm of this type by satellite is generally noticed a characteristic suite of "bubbles" upward, consisting of clouds that rise between two and four kilometers above the upper level of the main cloud before back into the cloud mass. These bubbles indicate the presence in the storm, a strong upward current and very structured. However, a tornado will form only if the updraft of air starts to turn: this is what happens when the updraft concentrates the rotational movement of the horizontal winds of the troposphere .