When Nature Has Its “Eye” On Us

By Peter Collins-Brown

Editor’s Note: Bedford resident Peter Collins-Brown has been a weather fanatic all his life and decided early on that meteorology was the career for him. After graduating from Boston University with a degree in Chemistry, he earned a Masters in Atmospheric Science at the University of Lowell and become a member of the American Meteorological Society. Now he’s sharing his passion for the weather with The Bedford Citizen. Every other week or so, Peter will send a bit of an inside scoop on the weather—perhaps including the forecast for the upcoming week, how the weather works, and how it might impact your daily routine. 

So, what exactly is a hurricane and how does it form? Most of the hurricanes that we see here on the east coast of the US originate off of the west coast of Africa. A hurricane begins its life as something called a “tropical wave.”  This wave is caused by the heating of ocean water by the hot tropical sun, which, in turn, sends moisture skywards, forming large thunder storms—think of a kettle blowing off steam. As the hot air rises, it createsa void at the surface that lets surrounding air flow in to fill the space, creating both lift and spin.  The warmer the water and the air are, the more ocean water is evaporated and the storm begins to grow. As the storm grows, it begins to spin. This spinning motion, in turn, increases the speed of the winds inside the storm, and once the winds reach 39 mph, we have a tropical storm. If conditions continue to prove favorable and the winds reach 75mph, we have a full-fledged hurricane on our hands.

When should we in Bedford start to worry? If past history is any indicator, then those storms headed for the Bahamas have the best chance of riding up the east coast to New England. This is due, in part, to the eastward flow of weather systems across the lower 48 states. The steering currents from these systems tend to pick up storms that are in the Bahamas and pull them right up along the east coast. This is especially true when we hit mid-August through October. By late summer and early fall, the ocean temperatures along the east coast have reached their maximum, creating the conditions favorable for keeping storms active and growing as they move north. As a matter of fact, August has proven to be quite a month for New England for tropical storms and hurricanes. Just last year there was Hurricane Irene. In 1991, we had Hurricane Bob. And back in 1954, Connie and Diane, both Category 3 hurricanes, struck within three days of each other.

What makes things different today from back in the 1950’s is our enhanced capabilities for forecasting the path of these storms, so that people can take precautionary measures to minimize their impacts. Today, forecasters have access to multiple complex models, along with satellite images and real-time readings from the storms themselves provided by hurricane-hunting aircraft. What most people don’t realize is that, even here in Bedford, flooding from tropical rains can be the number one cause of property destruction and loss of life—you don’t have to live on the beach to be impacted by flooding. Storm surges caused by tropical storms can back water up in the Merrimack River and cause major flooding along its tributaries, especially the Shawsheen.  So, stay tuned to your local weather—the next tropical wave could be headed our way.