In just about a month the spring equinox will be here. WeÕll be headed toward summer. Already this seasonal change is being heralded by swelling tree buds, daffodils, flowering quince and redbuds. Winter birds are beginning to migrate north and mockingbirds are singing and setting up their territories. Even though there can still be frosts and freezes for a while longer, the earth has orbited farther around the sun and it shines higher in our sky each day. The day length is increasing and the sunÕs radiation is striking the earth more directly, gradually warming its surface. Changes are also beginning to occur in the path of the upper level winds called jet streams, limiting excursions of arctic air into the south land.
Earth is covered by a very thin veneer of air, but it doesnÕt lie quietly upon the surface of our planet. Like waves in the ocean our atmosphere is almost a living thing, flowing in currents, rippling, spinning and surging up and down. As air masses flow over the uneven places of the globe - its mountains and hills - it is sometimes forced upwards. The heated land surface causes the atmosphere to warm, become less dense and portions of it to rise. Whether because of thermal instability caused by solar heating or uplift forced upon it by land masses, the water vapor in the rising air condenses and clouds form. Most of them are benign drifting puffs of cotton candy taking on the shapes of sheep and whatever else our imagination dictates. However, when thermal instability is high, the moisture content sufficient and rising air currents rapid and strong, bubbles of warm air take on a life of their own and developing clouds feed their need for warmth by releasing heat through condensation that is used to further strengthen them. Updrafts at the surface of the land sweep huge quantities of energy into the skies and what started as simple white puffs begin to tower higher, rolling, soaring, billowing and growing darker as their moisture content increases. A thunderstorm has formed. Winds aloft and newly formed raindrops interact moving electrons from place to place in the cloud. Imbalances in electrical charge develop and gigantic sparks of lightning leap through the clouds and to the ground. We hear the shock waves of these blasts of natural electricity as thunder first rumbling in the distance, then growing in volume to ear splitting cracks as the storm moves toward us.
The first thunderstorm cloud may be joined by others that form, grow, mature and dissipate. The thunderstorm, at first merely interesting, now commands our attention and may tower into the heavens to 50,000 feet or higher with rain reaching out ahead of it. Bursts of downward rushing cold wind whip trees, the sky blackens and hail as large as eggs may lash the ground. In the worst case scenario, sinuous, rolling horizontal masses of air twist upwards and the lower portions of a thunderhead begin to rotate. The rotating air gains speed and descends to the earth as a swirling, funnel-shaped vortex. The cotton candy has spawned a tornado, ravaging across the countryside with internal winds as high as 318 miles per hour, roaring and bellowing across the land. Trees are ripped from the ground, roofs sail through the air, cars are snatched up and thrown like toys, entire communities disappear and people die.
The months of April, May and June are periods during which nature exhibits its power to the maximum and puny humans and their works often receive severe lessons in humility and perspective. In the face of rampant natural forces, our enterprises take on a distinctly diminished stability and permanence. What is here now and seemingly always has been, can be gone or reduced to rubble in moments.
My next few columns will deal with severe storms - what kinds there are, how they form, what they can and cannot do, how to recognize them, how to protect yourself and your belongings from them and what to do if you are caught by one. Yes it is spring in the fields and forests of East Texas and it is also a time to prepare. Severe storms are a fact of life in this part of the country, so get ready to enjoy the ones that are no threat, avoid those you can and survive any you cannot escape. Generally, spring and early summer are pleasant times here and in the absence of damage and death, even severe storms have great beauty and aesthetic magnetism. Enjoy the sights and fragrances of spring flowers and the sounds of bird songs, but prepare also to be mesmerized by the spellbinding majesty of some of weatherÕs greatest spectacles.