Weather Tidbits: How a Tornado Forms

In this edition of Weather Tidbits, we’ll be discussing how tornadoes form. A proper environment for tornadic development features an unstable airmass and vertical speed and directional wind shear, or the change of wind speed and direction with height. Speed shear forces a horizontal column of air to rotate, and the updraft from the thunderstorm orientates the rotating column of air in a horizontal axis. At this point, directional shear will enhance this rotating column. A wall cloud will then form, and the rotating air column continues to build down. If it doesn’t reach the ground, it’s a funnel cloud. If it does, it’s a tornado. This touchdown is easier to achieve if the cloud base is low, which will usually be the case on days with high humidity and dewpoint temperatures.