Marty Sachnik, age 7, of Houston, Texas, for his question:

How can they tell the weather ahead of time?

Maybe you watch the weather news on TV. The weatherman often shows us a photograph taken by an orbiting satellite. This view is a wide wide picture of the globe. It may show a fluffy white patch of clouds over the western mountains or a stormy swirl over Alabama. There may be clouds streaming up to Houston from the Gulf of Mexico. All these cloudy patches are moving from here to there. The weatherman can tell which way they are moving and when they are expected to arrive over your city. He also knows whether a patch of clouds is likely to bring a storm or a gentle drizzle. The spaces between the clouds will bring clear skies as they drift overhead.

The weather bureau gathers news from far and wide. Countless weather stations report storms and other events. When the experts know the direction of the traveling weather they can predict it ahead of time. And over North America, most of our weather comes from the west. That storm over the western mountains is likely to march eastward, maybe to Texas. As a rule, the weatherman can predict if and when a storm will arrive. But the clouds over Alabama probably sailed over your head a few days ago. They are moving away, eastward toward the Atlantic.