Global Winds and Texas Weather

By the end of this lesson, you will be able to describe how large, worldwide patterns of moving air shape the weather you feel in your own town.

Air is always moving because the Sun heats Earth unevenly. The equator receives sunlight almost straight on, so the air there gets very warm, becomes less dense, and rises. Near the poles, the air is cold, dense, and sinks. This rising and sinking sets up convection currents, which are loops of moving air created when warm material rises and cool material sinks. Because Earth spins, these loops do not travel straight north and south. The spin curves them, creating prevailing winds, which are winds that blow from the same general direction most of the time in a region.

Texas sits in the belt of prevailing westerlies, winds that generally push weather systems from west to east across the state. That is why a cold front spotted over the Panhandle today often reaches Dallas or San Antonio tomorrow. Higher up, about ten kilometers above your head, a fast ribbon of air called the jet stream races along and steers storm systems. When the jet stream dips south in winter, frigid Canadian air can spill into Texas and drop temperatures fast.

Here is an example you know well. On a summer afternoon in Houston or Corpus Christi, warm, moist air blows in off the Gulf. That moisture rides the global wind pattern inland, builds into towering clouds as it rises and cools, and dumps a short, heavy thunderstorm around four o'clock. The same global system that spreads moisture around the planet is the reason your baseball practice gets rained out.

So local weather is not random. It is the small, nearby result of enormous air movements circling the whole Earth.

Try it: if prevailing westerlies move weather from west to east, and a thunderstorm is over El Paso this morning, which Texas cities should watch the sky next?