What Are the Weather Conditions Like Before a Tornado?

Tornadoes are extremely unpredictable weather systems that often develop with little warning and leave behind a trail of destruction. The strongest tornadoes can lift homes off their foundations, overturn trains and carry cars more than 300 feet. Recognizing the weather conditions that spawn tornadoes gives you time to seek shelter until the danger passes.

Tornado Weather Conditions

• Tornadoes form when a warm, humid air mass meets a cold front. As the warm air rises, the cool air moves in to replace it, and a whirling rotation begins. Eventually this rotation of air gathers strength and a funnel develops. A dark, low wall of clouds is often visible in the sky before a tornado forms. Weather conditions that precede tornado activity commonly include rain, lightning, strong winds and even hail. These severe weather conditions can be followed by an eerie calm right before the tornado hits.

Watches Versus Warnings

• Tornadoes usually travel from southwest to northeast, but they can also change their paths quickly or even backtrack over previously covered ground. The unpredictable nature of tornadoes illustrates the importance of staying alert, not only to weather conditions, but also to tornado watches and warnings. A tornado watch means the conditions in the atmosphere are conducive to tornado formation, but no actual tornadoes have been reported. A warning, by contrast, means a tornado has been spotted. Meteorological services usually sound a siren for tornado warnings. Tornadoes also create their own warning, a loud rumble that has been compared to the sound of a freight train.

Finding Safety Indoors

• Flying debris poses the greatest danger during a tornado. If weather conditions indicate a tornado is likely, be prepared to move quickly to the basement. Sturdy furniture, such as a heavy workbench, can provide added protection. Stairwells also provide a safe place to wait out the storm. If the building has no basement, move to an area away from windows on the lowest floor. Interior hallways, bathrooms and closets are all good choices. Once in a safe spot, crouch down and cover your head with your hands.

Finding Safety Outdoors

• When you are driving, watch for visible signs that indicate tornadoes are likely. In addition to the low bank of dark clouds, you may see whirling debris on the ground. Due to the unpredictable paths of tornadoes, it's best not to try to escape them in your car. A better choice is to look for shelter in a sturdy building. If no buildings are available, park your car and move away from it and from any trees, which can easily be blown over. Lie on the ground with your face down and your arms over the back of your head. Bridges do not provide safe shelter, because they cannot protect you from flying debris.