Weaker than expected Atlantic hurricane season ends

The 2013 Atantic hurricane season officially ended on Saturday as the quietest since 1982 and the sixth least active since 1950, the US National Oceanographic and Atmospheric Administration said. Thirteen tropical storms formed since early June in the Atlantic but only two, Ingrid and Humberto, reached hurricane strength. While the number of named storms topped the historical average of 12, the number of hurricanes were well below the historic average of six medium-strength category one or two storms and three major category three storms and above. Category three hurricanes have wind speeds of at least 110 miles (178 kilometers) per hour, while a category four storm can pack winds of 130 miles (210 kilometers) per hour or more. The most damaging are category five storms with winds of at least 155 miles (250 kilometers) per hour. ?This unexpectedly low activity is linked to an unpredictable atmospheric pattern that prevented the growth of storms by producing exceptionally dry, sinking air and strong vertical wind shear in much of the main hurricane formation region, which spans the tropical Atlantic Ocean and Caribbean Sea,? said Gerry Bell, NOAA's lead hurricane forecaster. ?Also detrimental to some tropical cyclones this year were several strong outbreaks of dry and stable air that originated over Africa.? NOAA had predicted in May that 2013 would be more active than usual, with 13 to 20 tropical storms, and three to six hurricanes.