Deadly late-season Atlantic hurricanes growing more frequent

Luckily for the Eastern U.S., many of the hurricanes that headed our way were deflected by weather fronts.

http://www.wunderground.com/blog/JeffMasters/comment.html?entrynum=1698

Posted by: JeffMasters, 1:40 PM GMT on November 17, 2010

it's been another remarkably active November in the tropics this year. The formation of Hurricane Tomas this month marks the fourth consecutive year in the Atlantic with a hurricane occurring November 1 or later. We had Category 1 Hurricane Noel in 2007, Category 4 Hurricane Paloma in 2008, Category 2 Hurricane Ida in 2009, and now Category 2 Tomas in 2010. This is the first time since beginning of reliable hurricane records in 1851 that there have been four consecutive years with a late-season November or December hurricane in the Atlantic. The previous record was three straight years, set in 1984 - 1986. It used to be that late-season hurricanes were a relative rarity--in the 140-year period from 1851 - 1990, only 30 hurricanes existed in the Atlantic on or after November 1, an average of one late-season hurricane every five years. Only four major Category 3 or stronger late-season hurricanes occurred in those 140 years, and only three Caribbean hurricanes. But in the past twenty years, late-season hurricanes have become 3.5 times more frequent--there have been fifteen late-season hurricanes, and five of those occurred in the Caribbean. Three of these were major hurricanes, and were the three strongest late-season hurricanes on record--Lenny of 1999 (155 mph winds), Paloma of 2008 (145 mph winds), and Michelle of 2001 (140 mph winds). Of course, the number of storms we are talking about is small, and one cannot say anything scientifically significant about late-season Atlantic tropical cyclone numbers, unless we include storms from late October as well. This was done, though, by Dr. Jim Kossin of the University of Wisconsin, who published a 2008 paper in Geophysical Research Letters titled, "Is the North Atlantic hurricane season getting longer?" He concluded that yes, there is an "apparent tendency toward more common early- and late-season storms that correlates with warming Sea Surface Temperature but the uncertainty in these relationships is high". The recent increase in powerful and deadly November hurricanes would seem to support this conclusion.

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