The names of weather systems can get somewhat confusing because of their tendency to overlap. All circling weather patterns with low-pressure centers are technically referred to as cyclones. This means that hurricanes and tornadoes fall under the cyclone designation. Cyclone can refer to anything in the category that fits that description, no matter its power or size. Also, within this category are middle-latitude (or midlatitude) cyclones -- huge weather systems that can cover a continent.
Remember that storms referred to as hurricanes in certain parts of the world are commonly called cyclones in other regions and typhoons in the remaining areas. A hurricane begins east of the international date line, and typhoons spawn to the west of it. If you're in the Indian Ocean, you have yourself a cyclone.
The Calm Before the Storm
So is there a calm before the storm? You may have already guessed the answer. Sometimes there is; sometimes there isn't. Under the right conditions, an eerie or peaceful calm will befall your picnic before a storm moves in. Other storms skip the calm and proudly announce their presence by instantly unleashing bad weather. Let's take a look at what goes on inside a storm to understand more about how this works.
Storms need warm, moist air as fuel, and they typically draw that air in from the surrounding environment. Storms can draw in that air from all directions -- even from the direction in which the storm is traveling.
As the warm, moist air is pulled into a storm system, it leaves a low-pressure vacuum in its wake. The air travels up through the storm cloud and helps to fuel it. The updrafts in the storm, however, quickly carry the air upward, and when it reaches the top of the cloud mass, this warm moist air gets spit out at the top. This air is sent rolling out over the big, anvil-shaped head of the thunderclouds or the roiling arms of hurricanes. From there, the air descends -- drawn back toward lower altitudes by the very vacuum its departure created in the first place.
What's important for our purposes is that descending air becomes warmer and drier (a good thing after its trip through the cloud, which involved cooling and condensation). Warm, dry air is relatively stable, and once it blankets a region, it stabilizes that air in turn. This causes the calm before a storm.
On the other hand, different situations can produce weather that's quite a bit uglier and not at all calm before a storm hits. For example, think of large storm systems. They're more complex than a single, unified storm, and their interactions usually don't produce any type of calmness.
Though we understand weather better than in years past, predicting it with perfect accuracy (calm or not) still remains somewhat of a mystery. For more information about storms and weather, visit the links on the next page.