HURRICANES, MONSOONS, AND TROPICAL STORMS

What was the Perfect Storm?

The subject of a 1997 novel by Sebastian Junger, as well as a 2000 movie starring George Clooney, Diane Lane, and Mark Wahlberg, the Perfect Storm was also a real, terrifying event. During the last days of October 1991, an extratropical cyclone organized itself several hundred miles off the coast of Nova Scotia. At the same time, Hurricane Grace—a relatively weak category 2 hurricane—moved toward this storm from the south. As Grace approached the northern cyclone, the winds from the cyclone did something unusual. Typically, tropical hurricanes will tend to move away from the shoreline as they move north, but the cyclone winds, spinning in a northeastern swirl, blew Grace toward the Northeast Coast. The two storms merged and became known as the 1991 Halloween Nor'Easter.

The result was one of the most destructive storms in history, with winds up to 65 knots (75 miles per hour or 120 kilometers per hour) and ocean waves up to 39 feet (12 meters) high. A dozen people died in the storm (including the six crew members aboard the swordfishing vessel Andrea Gail, the subject of Junger's novel) and one billion dollars in damages were incurred. In another unusual twist, the Halloween Nor'Easter had turned into a hurricane by November 1, an event that is quite uncommon for an extratropical low pressure system, though not unheard of. The new hurricane, however, remained unnamed because the National Weather Service thought it might be confusing to the American media to rename the Halloween Nor'Easter.

What are monsoons?

Occurring in southern Asia, monsoons are winds that flow from the ocean to the continent during the summer and from the continent to the ocean in the winter. The winds come from the southwest from April to October, and from the northeast (the opposite direction) from October to April. The summer monsoons bring a great deal of moisture to the land. They cause deadly floods in low-lying river valleys, but also provide the water southern Asia relies upon for agriculture.

What is the origin of the word "monsoon"?

The word "monsoon" comes from the Arabic word "mausin," meaning season.

What is an Alberta clipper?

An Alberta clipper is a storm that develops on the Pacific front, usually over the Rocky Mountains of Alberta, Canada. This quick-moving storm moves southeast into the Great Plains, leaving a trail of cold air and snow.

What is a Siberian express?

This term describes outbreaks of arctic air that are severely cold; they descend from northern Canada and Alaska to other parts of the United States.

What is a hurricane?

A hurricane is a tropical storm that has winds of 74 miles per hour or more that forms in the Atlantic Basin. Hurricanes typically occur in the North Atlantic and Caribbean Sea during the months of July, August, and September, when warm surface ocean temperatures exceed 80°F (26.5°C), providing energy that feeds into the storm. Seawater evaporates into the air, creating clouds, while the Coriolis effect causes the clouds to rotate.

For a hurricane to develop, there must not be a lot of difference in wind speeds in the upper and lower elevations of the storm. If there is a big difference in these speeds, the resulting wind sheer will cause the hurricane to become unstable, with clouds and winds opposing each other rather than working together in a gigantic swirl that increases in speed. Hurricanes do not tend to generate close to the equator (within five degrees latitude) because the Coriolis effect is stronger father away from the equator, and also because they need a low pressure area that is not close to the equator.

 
< Prev   CONTENTS   Next >