June 1 to November 30, 2005
As 2007 approaches, the southeastern United States is experiencing an extreme to abnormal drought. The year also saw tropical cyclones—tropical depressions, tropical storms, and hurricanes—that often flooded parts of the East Coast and the Gulf of Mexico. Tropical cyclones don't just hit one place. They can come ashore across a large swath of coastline and then move inland, causing torrential rains for hundreds of kilometers. Tropical cyclones, although relatively rare, contribute significantly to seasonal rainfall accumulation in the southeastern United States. In a recent study, Dr. Marshall Shepard of the University of Georgia and his collaborators found that tropical storm systems contribute an average of 13 percent of total rainfall during hurricane season. Relatively few storms made landfall in the southeastern United States during the 2006 and 2007 hurricane seasons, which may have contributed to the drought.
Fortunately, it won't take the devastation of a major hurricane to break the drought. Shepard and his colleagues found that while major hurricanes (Category 3, 4 or 5) dump more rain in a single day than other storms, weaker hurricanes, tropical storms and depressions accumulate rainfall throughout the hurricane season. accounts for a larger proportion of the volume. Shepard analyzed rainfall data collected by the Tropical Rainfall Measuring Mission (TRMM) satellite between 1998 and 2006. They found that, on average, the wettest months are September and October, which are also the most active hurricane months. The most unusual rainy days of that period were caused by some kind of tropical system. Because weaker systems occur more frequently, they contribute more to the season's rainfall totals than severe storms .
These results were demonstrated during the 2005 hurricane season, a record year in the Atlantic. From June to December, 31 tropical cyclones formed, more than in any year recorded by the National Hurricane Center. According to the National Hurricane Center, there are seven major hurricanes during the hurricane season (June to November), including the strongest Atlantic storm ever recorded (Hurricane Wilma) and the costliest hurricane (Hurricane Katrina). ).
This image shows the total rainfall observed by TRMM for the season. The highest total is dark blue, while the lowest total is white. Overall, rainfall totals are highest after minor storms. The heaviest areas of heavy rainfall were over the Atlantic Ocean in the path of Hurricane Ophelia, a weak Category 1 hurricane. In comparison, larger storms, such as Hurricanes Rita, Katrina, and Dennis, produce less rainfall. While the general trend is for small tropical cyclones to contribute significantly to precipitation totals, other factors, including more frequent light rainstorms, may have influenced the 2005 pattern.
