What makes Hurricane Harvey so uniquely strong? Does the storm represent a new norm in extreme weather?
How much is 50 inches of rain?
Houston and surrounding cities recorded between 25-27 inches of rain in just 24 hours and 15-20 inches more are expected throughout the week. For comparison, Houston ordinarily sees around 50 inches of rain in a year. That means half of a year’s worth of rain fell in a single day, with potential for an entire year’s worth of rain over the course of just one week.
To look at this level of rainfall another way, an estimated 9 trillion gallons of water has fallen over the greater Houston area. As calculated by the Washington Post, this is enough water to cover the entirety of the contiguous 48 states in 0.17 inches of rain or to fill the Great Salt Lake twice.
The level of flooding is thus severe and photos have already shown cars and entire highways submerged, as well as residents navigating city streets in boats. Adding to the problem, Galveston Bay can no longer serve as a source of drainage for the excess water since it too was elevated by Harvey’s storm surge.
Along with the high levels of rainfall and the significant storm surge associated with Hurricane Harvey, the longevity of the storm over the Houston area is even further contributing to the extreme levels of flooding. There is a lack of winds to force the hurricane inland, but rather multiple areas of high-pressure winds in the upper atmosphere that have essentially left the storm trapped above the Texan coastline for several more days. 5-10 trillion more gallons of rain are expected before the storm is done.
Modeling hurricane patterns is incredibly complicated.
Is climate change to blame for the intensity of Hurricane Harvey?
Modeling hurricane patterns is incredibly complicated, but of course predictions based on climate change models are even more complex. Thus, it’s not as simple as drawing a clear connection between a single storm event and the complex web of activity that results from climate change.
However, we do know that an increase in the intensity and frequency of weather events is one of the main predictions of climate change models. In particular, hurricanes are fed by warm, moist air at the ocean’s surface. This can lead to hurricanes losing intensity before making landfall if they churn up enough deeper – and thus cooler – ocean water leading to a decrease in surface air temperature. Harvey, however, was fed by water from the Gulf of Mexico that has been reported as unusually warm this year, perhaps due to record high temperatures associated with global warming.
For more information on Hurricane Harvey, news outlets like the New York Times and the Washington Post have lifted their paywall for news relating to the storm. The United States Geological Survey is tracking the changes made to the coastline by Hurricane Harvey through dune erosion, overwash (the inland movement of sand over the tops of coastal dunes), and inundation (the submersion of shoreline).
Until next time, this is Sabrina Stierwalt with Ask Science’s Quick and Dirty Tips for helping you make sense of science. You can become a fan of Ask Science on Facebook or follow me on Twitter, where I’m @QDTeinstein. If you have a question that you’d like to see on a future episode, send me an email at email@example.com.