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The South Carolina Coast Guard captures images of the major flooding brought on by Hurricane Harvey during rescue operations August 31, 2017. Harvey\u2019s track nearly stalled over Texas as it continued to drop record-breaking rainfall over Houston and surrounding areas. Credit: U.S. Air National Guard Staff Sgt. Daniel J. Martinez<\/p><\/div>\n
\u201cJust a 10 percent slowdown in hurricane translational speed can double the increase in rainfall totals caused by 1 degree Celsius of global warming,\u201d says Kossin, a researcher at the National Oceanic and Atmospheric Administration\u2019s (NOAA) Center for Weather and Climate. He is based at the University of Wisconsin-Madison.<\/p>\n
The study compared 68 years (1949-2016) of worldwide hurricane track and intensity data, known as best-track data from NOAA<\/a> to identify changes in translational speeds. It found that, worldwide, hurricane translational speeds have averaged a 10 percent slowdown in that time.<\/p>\n One recent storm highlights the potential consequences of this slowing trend. In 2017, Hurricane Harvey stalled over eastern Texas rather than dissipating over land, as hurricanes tend to do. It drenched Houston and nearby areas with as much as 50 inches of rain over several days, shattering historic records and leaving some areas under several feet of water.<\/p>\n How much hurricanes have slowed depends on where they occur, Kossin found. He says: \u201cThere is regional variation in the slowdown rates when looking at the 10 percent global average across the same timeframe.\u201d<\/p>\n The most significant slowdown, 20 percent, occurred in the Western North Pacific Region, an area that includes southeast Asia. Nearby, in the Australian Region, Kossin identified a reduction of 15 percent. In the North Atlantic Region which includes the U.S., Kossin found a six percent slowdown in the speeds at which hurricanes move.<\/p>\n When comparing hurricane tracks during their time over land and water, the study reveals regional variability in the slowdown rates of hurricane translation speeds. Credit: NOAA National Centers for Environmental Information.<\/p><\/div>\n When further isolating the analysis to hurricane speeds over land, where their impact is greatest, Kossin found that slowdown rates can be even greater. Hurricanes over land in the North Atlantic have slowed by as much as 20 percent, and those in the Western North Pacific as much as 30 percent.<\/p>\n Kossin attributes this, in part, to the effects of climate change, amplified by human activity. Hurricanes move from place to place based on the strength of environmental steering winds that push them along. But as the Earth\u2019s atmosphere warms, these winds may weaken, particularly in places like the tropics where hurricanes frequently occur, leading to slower-moving storms.<\/p>\n Additionally, a warmer atmosphere can hold more water vapor, potentially increasing the amount of rain a hurricane can deliver to an area.<\/p>\n The study complements others that demonstrate climate change is affecting hurricane behavior.<\/p>\n For instance, in 2014, Kossin showed that hurricanes are reaching their maximum intensities further from the tropics, shifting toward the poles<\/a> in both the Northern and Southern Hemispheres. These shifts can deliver hurricanes to areas \u2013 including some heavily-populated coastal regions \u2013 that have not historically dealt with direct hits from storms and the devastating losses of life and property that can result.<\/p>\n![\"\"](\"http:\/\/www.ssec.wisc.edu\/news\/wp-content\/uploads\/sites\/19\/2018\/06\/infographic-regional-slowdowns-of-tropical-cyclone-movement-1949-to-2016-noaa-ncei-600x366.png\")