Jeff Moots, age 12, of Gallup, New Mexico, for his question:

How does a tornado get started?

A tornado gets started up there in a stormy sky and where there is one there are likely to be others. Scientists know that certain weather conditions are needed to start them, though they are not sure of all the details. However, they do know that a tornado is the fiercest of all weather events. True, it is quite small, but its winds are stronger than the strongest hurricane.

Though a tornado is a very small storm, it belongs to an enormous weather system, which may spread over several states. Often the signs in the sky are ragged, dirty grey clouds blotched with errie yellow sunlight, strewn around islands of blue. This usually means that trouble in the weathery atmosphere is building up on a huge scale.

Imagine a gigantic mass of air, wide enough to spread across several states and tall enough to reach up six or seven miles. It is cool, dry air traveling rather fast and minding its own business. But unfortunately it is not alone up there in the sky. Sprawled across its path is a gigantic mass of warm, moist air.

Stormy weather builds up when different air masses collide and clash up there in the sky. In tornado weather, the great mass of warm air is thin and light. Bubbles of this light warm air tend to form near the ground and float upward in rising currents. The great mass of cooler air is heavier and tends to stay close to the ground. Around the world, such masses of air meet every day. As a rule, the heavier mass wedges its way under the warm air.

In tornado weather, this peaceable settlement does not happen. Instead, the two opposite air mass meet in a head on collision. The cool heavier air runs up and over the mass of warm, lighter air. This creates a whole skyful of trouble. For the warm light air naturally tries to rise upward through the heavier layer above it.

Here and there, bubbles and currents of warm air do manage to rise up through the heavier air. But meantime, the spinning earth causes the rising air to twist to the right. Its spinning force is so strong that a rising current is twisted around and around like a twirling rope. This is when a twisting tornado gets started.

Soon there are pockets of spiralling winds reaching up from the ground to the stormy clouds high overhead. Here and there, a windy pocket spins the grey cloudy material into a funnel, shaped like an elephant's trunk. The grey tip dips down, weaving and waving towards the ground. If it touches the ground, its wild, wild winds plow a path of destruction.

In this big weather system, dozens of columns of light warm air try to rise up through the heavier air aloft. Many of them wear themselves out before they get very far. But sad to say, others manage to start breezy pockets of spinning winds. First one, then a series of devastating tornados may strike through several states.