Hurricanes are moisture sucking whirlwinds, born at sea, and carrying a destructive wallop of whipping wind and water to dump upon coastal islands and towns. In other parts of the world, the words Typhoon and Cyclone are preferred, but over all the word hurricane, from the dark and destructive god Hurakan, is becoming the most often used name of these giant storms. Katrina is only the latest and greatest of such storms in the USA.
Hurricanes form when sea water heats and then meets cooler air. The ocean surface must rise to such a degree (over 80 degrees F.) that it is swept up and collected into winds that begin to spin. In northern hemispheres they move counter clockwise, and in southern hemispheres they move clockwise, in keeping with the rotation of the earth.
The life cycle of a hurricane consists of 1, heating ocean surface, 2, air pressure collision, 3, collection of moisture from water surface, and 4, spiraling all into a swirling massive storm which moves toward shorelines. Then, in its final act, 5, the hurricane hits cooler land temperatures and breaks up unable to feed off the heat and moisture any further.The life cycle is one of collecting more and more moisture, whipping it upward, and forming vast and swirling clouds that spin ever faster around the calmer "eye."
The relatively calm, eye of the storm can be thought of as the center around which all movement takes place. The eye of the hurricane may be up to thirty miles wide, but it is small compared to the surrounding wall of circulating wind and water that can cover up to 650 miles across. As the storm hits land it generally begins to break up as the heat needed to sustain its force is drastically lost.
In the mid Atlantic this means the storms usually make land fall seasonally upon the coasts of the eastern United States and the Gulf of Mexico, often hitting north and central America with extreme ferocity. Here in the U.S, our Hurricane season is late summer until the end of fall.
This immense amount of moisture can bring waves up to 50 feet high, and solid walls of flooding rain that are dumped dramatically upon coasts. Scientists are actively investigating what part of increased ocean heat is caused by human activity. The latest conclusion is not that hurricanes are necessarily caused by global warming, or climate change, but that their severity is dramatically increased due to the excess heat they move about. Increased ocean temperatures from dead zones and El Nino’s are suspect too.
Although we tend to think of a hurricane as a stormy flying disc, they are in fact many miles high. As they build toward their most dramatic stage four, where they collect and swirl powerful winds the bands of moisture, called "rainbands", spiral ever inward at a faster pace.
The winds whipped up into a frenzy can reach speeds up to200 miles an hour, all the while hurling vast amounts of moisture and dropping it as heavy rain. The highest wind speed is at the storms upper reaches, and the inside “wall” of the eye of the hurricane has the fasted and heaviest weather of all.
Hurricanes are named alternately, with a male and a female name, a practice which allows major ones to be remembered easily. With a particularly huge hurricane, that name is retired from the list, so we will never see another “Katrina.” Coastal cities need to have firm and reliable plans of not just hurricane readiness, but all natural and man made disaster readiness planned far in advance. When hurricanes grasp with spiraling tendrils further inland, tornadoes are spawned from them at times.
What we can learn about such storms is that nature instructs us to beware of hot air, whether it come from political promises or off shore intense temperatures and air pressures. The two are related of course, when one thinks of how disaster ready most areas are (or are not) with area protection (maintaining natural sea barriers such as wetlands) evacuation, rescue, and reconstruction plans in place.
Hurricanes will come and flooding will occur, it is up to all of us to contain and manage just how much destruction they will carry with them with each new hurricane season.