El Nino and the 2014 Atlantic Hurricane Season


El Nino refers to a large-scale ocean-atmosphere climate phenomenon linked to a periodic warming in sea-surface temperatures across the central and east-central equatorial Pacific Ocean. This phenomenon affects the patterns of tropical rainfall from Indonesia to the west coast of South America, and subsequently weather patterns throughout the world.


Based on current model data, it appears that an El Nino event could develop near the height of this Atlantic hurricane season, and potentially inhibit some tropical storm development.  So, many forecasters and researchers are expecting a below-normal 2014 hurricane season for the Atlantic Ocean basin.


The change in winds with height is referred to as vertical wind shear.  Hurricane formation is normally enhanced when winds are fairly uniform throughout the atmosphere, which means vertical wind shear is low.  It becomes more difficult for hurricanes to develop as vertical wind shear increases.


When an El Nino occurs, upper level winds generally tend to increase in the August to October time period across the tropical North Atlantic Ocean, which leads to higher-than-average vertical wind shear and reduced hurricane activity.  Thus, during an El Nino event fewer hurricanes typically develop in the deep tropics from African easterly waves.  These are the weather systems that typically have a much greater likelihood of becoming major hurricanes, and of eventually threatening the U.S. and Caribbean Islands.


But even with El Nino present, strong tropical cyclones can still occur.  One only needs to remember years such as 1992 during which an El Nino was in progress and only seven named tropical storms occurred.  One of those, however, was Category 5 Hurricane Andrew which devastated Miami and surrounding areas of South Florida. And in 2004, although a weak El Nino event developed, Florida suffered direct hits by Hurricanes Charley (Category Four), Frances and Jeanne (Category Three).


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