MEMPHIS, TN (WMC) - Two major hurricanes, Irma and Harvey, have been making headlines over the past few weeks. Although hurricane season begins on June 1 and lasts until November 30, late August and September are considered the peak months of the season.
For the first time ever, two category 4 hurricanes made landfall in the United States. In addition, this is the first time that a category 4 storm hit the U.S. since Charley in 2004.
Harvey made landfall near Rockport, TX as a category 4 hurricane on August 25. Harvey meandered along the gulf coast of Texas for days and resulted in one of the most disastrous flooding events in U.S. history. Harvey produced another first this hurricane season—highest rainfall produced by a tropical system in the contiguous U.S. As Harvey sat along the coast as a tropical storm, Louisiana and Texas received more than 40 inches of rain.
So why is this season so active for the United States? It has a lot to do with atmospheric flow, warm waters and luck. These systems developed off the coast of Africa and that path typically results in some of the most destructive tropical cyclones. A high pressure system sits off the east coast of the U.S. and that clockwise flow pulled these hurricanes into the warm waters of the northern Atlantic basin.
Although this was a significant season based on landfall in the United States, this is not considered one of the most active seasons. In 2005, there were five major hurricanes that made landfall and two of those were in the U.S. Those two were Katrina and Wilma.
Based on number of named storms, there would need to be at least 15 for 2017 to rank in the top 20 most active. There have been 12 as of September 12th. There have been 6 hurricanes so far this season, but the top ten seasons on record have a minimum of 10.
However, Harvey and Irma did break several notable records that will place it on top of many lists. With three days as a category 5, Irma was the longest category 5 hurricane on record. In addition, Irma maintained 185 mph and above winds for longer than any other hurricane. Also, the cost of Irma and Harvey are expected to be some of the costliest hurricanes on record. This could make it the costliest hurricane season on record, but it will likely take weeks for the damage costs to be truly known. The most costly is currently Katrina in 2005.