Posted by: coastlinesproject | October 4, 2012

Nadine, weakens, Oscar not a threat. Let’s hope we can run out the clock on this hurricane season!

The Peak of the Season

Hurricanes

September 28, 2012

When I give talks about erosion I often ask my audiences what they think is the most likely state to get hit by a major storm in any particular year. It is a trick question, of course. Most people automatically think Florida or North Carolina because of hurricanes, but the correct answer is actually Massachusetts because Cape Cod juts so far out into the Atlantic that it gets whacked by both hurricanes in the summer, and Northeasters in the winter.

Northeasters usually cause the most erosion, because they linger around through several tidal cycles, but a good strong hurricane like the Perfect Storm of 1991 or the 1938 Hurricane can cause considerable damage from other causes. The 1938 hurricane killed over 600 people; most of them were actually swept off of beaches in New England because weather forecasting was so primitive there had been no warnings of the impending storm. The beach goers thought they were looking at an offshore fog bank. It was the fast approaching 30-foot storm surge instead.

Such a storm would cause considerably more damage today, because so many people now live along our coasts. Such storms are expected to become more common as global warming heats surface layers to over 80 degrees Fahrenheit on a regular basis. By late May of 2012, those conditions had already occurred in the Atlantic several weeks earlier than normal, so I had been anticipating a long and severe hurricane season.

Hurricanes Alberto and Beryl had struck even before the season got officially underway on June 1st.  They were the strongest hurricanes to ever hit in the preseason.

Everyone remembers Isaac because it caused Republican Pooh-Bahs so many fits and more hurricanes kept forming as we approached the peak of the season on September 1st.

But then something strange had happened. After Hurricane Leslie had brushed the shore, much to the delight of East Coast surfers, the season just seemed to peter out. By late September hurricanes Michael and Nadine were just circling around aimlessly in the mid-Atlantic. There should have been half a dozen potential hurricanes determinedly marching across the ocean at that time of year.

What had happened? The extreme La Nina pattern that had led to the hottest year on record had finally started dissipating to be replaced with the more familiar El Nino. This Pacific Ocean oscillation also causes the Jet Stream to bulge out over the Atlantic Ocean. This had helped spawn a series of windstorms that had swept a massive swath of hot, dusty, dry air off the Sahara Desert and into the Atlantic Ocean. Particles of dust and sand had fallen on Florida, Texas, England and Italy.

It reminded me of when I was doing research on an oceanographic vessel 200 miles off Africa. Every morning I would have to get up early and hose several millimeters of sand and grit off the decks that had been blown off the Sahara Desert the night before.

But the September layer of hot, dusty air had apparently choked off the system that breeds hurricanes. During the hot summer months, swarms of thunderstorms usually form over Africa and then sweep out to sea where they start to pull warm moist Atlantic air up through giant vortices of spinning winds that can become full-blown hurricanes. But hot dry air and shear winds will prevent the vortices from getting organized into tropical storms and hurricanes.

In the mid 1980’s, William Gray discovered that there was a correlation between weather patterns in Northwest Africa and the frequency of hurricanes in the Atlantic. The Colorado State researcher showed that when the Sahara Desert was expanding and the Sahel region of Africa was hot and dry, fewer major storms struck the East Coast of the United States.

This pattern had occurred for 26 years from 1966 to 1992 when only three major hurricanes lashed the East Coast, but from about 1944 to 1960 the Sahel had been wet and stormy and the Atlantic had had 15 major storms. They had peaked on Cape Cod in 1954 with hurricane Carol, Edna and Hazel and in 1955 with Connie and Diane. Those were exciting times to be a kid on Cape Cod.

But by the time the pattern had switched back to more hurricanes in 1995 I was a homeowner and considerably less enthused. This switch had happened with a bang with Hurricane Andrew and continued through such damaging hurricanes as Katrina, Rita, Wilma and Charlie. At the time of the shift William Gray had estimated that it would last from ten to forty years.

But had it only lasted for seventeen years? Does the swath of hot, dusty, dry Sahara air signal that the system has switched back to the pattern of fewer hurricanes that we had experienced from 1966 to 1994? It undoubtedly an artifact of old age and, ahem, responsibility that I am hoping that this is the case while my son; an avid East Coast surfer wishes that it is not. Ah youth, so wasted on the young!

At any rate, if have entered a pattern of fewer hurricanes we can thank this oscillation for providing us with a brief reprieve so we can continue our strategic retreat from the coasts in a graceful and dignified manner.

—–

William Sargent is a NOVA consultant and author of 18 books including The House on Ipswich Marsh and Beach Wars; 10,000 Years on a Barrier Beach. They are available through local bookstores and at www.strawberryhillpress.com. See Strwberry Hill tab at the top of this page.

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