ENGINEERING

Four U.S. land-falling storms include devastating Sandy and Isaac

 

November 30 marks the end of the 2012 Atlantic Hurricane season, one that produced 19 named storms, of which 10 became hurricanes and one became a major hurricane. The number of named storms is well above the average of 12. The number of hurricanes is also above the average of six, but the number of major hurricanes is below the average of three.

 

Based on the combined number, intensity, and duration of all tropical storms and hurricanes, NOAA classifies the season as above-normal. 2012 was an active year, but not exceptionally so as there were 10 busier years in the last three decades.

 

This season marks the second consecutive year that the mid-Atlantic and Northeast suffered devastating impacts from a named storm. Sandy, and Irene last year, caused fatalities, injuries, and tremendous destruction from coastal storm surge, heavy rainfall, inland flooding, and wind. Storms struck many parts of the country this year, including tropical storms Beryl and Debby in Florida, Hurricane Isaac in Louisiana, and post-tropical Cyclone Sandy in New Jersey.

 

“This year proved that it’s wrong to think that only major hurricanes can ruin lives and impact local economies,” said Laura Furgione, acting director of NOAA’s National Weather Service. “We are hopeful that after the 2012 hurricane season, more families and businesses all along the Atlantic and Gulf coasts become more “weather ready” by understanding the risks associated with living near the coastline. Each storm carries a unique set of threats that can be deadly and destructive. Mother Nature reminded us again this year of how important it is to be prepared and vigilant.”

 

An interesting aspect of the season was its early start, with two tropical storms, Alberto and Beryl, developing in May before the season officially began. Also, this is the seventh consecutive year that no major hurricanes (Category 3, 4 or 5) have hit the United States. The only major hurricane this season was Hurricane Michael, a Category 3 storm that stayed over the open Atlantic.

 

Several storms this year were short in duration, weak in intensity, and went largely unnoticed by the general public because they stayed out over the Atlantic. A persistent jet stream pattern over the eastern portion of the nation helped steer many of this season’s storms away from the United States. The number of named storms and hurricanes was higher than predicted in NOAA’s pre-season outlook, in large part because El Niño – which likely would have suppressed overall storm activity – never materialized as predicted by many climate models.

 

Hurricane forecasters remind us that a well-established climate pattern puts us in an ongoing era of high activity for Atlantic hurricanes that began in 1995. Since that time, more than 70 percent of seasons have been above normal, including 2012. Historically, Atlantic high-activity eras have lasted 25 to 40 years, with the previous one occurring from the mid-1930s until 1970. Several inter-related atmospheric and oceanic factors contribute to these high activity years, including warmer Atlantic Ocean temperatures, an enhanced West African monsoon, and reduced vertical wind shear.

 

NOAA will release its pre-season outlook for the 2013 hurricane season in May.