Initial Conditions for the 2006 Atlantic Hurricane Season

Initial Conditions for the 2006 Atlantic Hurricane Season

June 1 marks the first official day of hurricane season in the Atlantic Ocean. In 2006, conditions in the Atlantic were “hurricane friendly,” said NASA scientist David Adamec, and not quite as extreme as they had been at the opening of the 2005 hurricane season. Hurricanes need both warm sea surface temperatures and calm winds to develop. Warm water provides both heat and humidity needed for storm formation. Strong winds would tear a developing storm apart, while calm winds allow a hurricane to build. In late May 2006, sea surface temperatures were warmer than normal, and winds were calm.

These images contrast sea surface temperatures on May 30, 2006, top, and May 30, 2005, bottom, as measured by the Advanced Microwave Scanning Radiometer-EOS (AMSR-E) on NASA’s Aqua satellite. Red colors show regions where waters were warmer than the twelve-year average (1985-1997), while blue indicates cooler-than-average temperatures. White indicates average temperatures. In 2006, temperatures in the Atlantic were slightly warmer than average, particularly in the Caribbean, but strong southwest trade winds stirred the Gulf of Mexico, keeping the surface waters cool, said Adamec. In 2005, by contrast, the entire hurricane-prone section of the Atlantic was much warmer than average. In fact, at the opening of the 2006 hurricane season, sea surface temperatures were 2 degrees cooler than they had been at opening of the 2005 season, said Adamec. The warm temperatures in 2005 allowed a record seven storms to form by the end of July, one of which, Hurricane Emily, set records when it became the first category 5 hurricane to occur in July. All other Atlantic storms of that strength have developed later in the season.

Though sea surface temperatures were not as extreme at the opening of the 2006 hurricane season as they were in 2005, the National Hurricane Center predicts a very active hurricane season with 13 to 16 named storms, 4 to 6 of which could become major hurricanes.

The other major difference between conditions in 2005 and conditions in 2006 is the position of the Bermuda High, a semi-permanent high-pressure system that sits over the Central Atlantic. Hurricanes that form in the Atlantic tend to circle the Bermuda High. In 2004 and 2005, the Bermuda High expanded to the south and west, pushing storms into the Gulf of Mexico and Florida. But as of May 31, 2006, the Bermuda High remained small and in a position that would steer storms up the East Coast of the United States or out into the Atlantic.

Sea Surface Temperature data from the Advanced Microwave Radiometer for EOS (AMSR-E), courtesy Remote Sensing Systems