This Is Actually The Biggest Killer During Hurricanes And Tropical Storms

Deaths from U.S. hurricanes, tropical storms and tropical depressions are more likely from water, not wind, despite how they're rated and classified, according to a study from the National Hurricane Center (NHC).

Seven of eight fatalities from tropical cyclones in the U.S. from 1963 through 2012 were from either storm surge, rainfall flooding or high surf, or occurred offshore within 50 nautical miles of the coast, the study by Dr. Ed Rappaport, deputy director of the NHC, found.

A tropical cyclone's winds or embedded tornadoes accounted for only 11% of fatalities in the U.S. during that time.

This may sound counterintuitive since Category 1, 2, 3 hurricanes are rated based on their maximum sustained winds.

(MORE: Saffir-Simpson Hurricane Wind Scale)

Certainly, a hurricane or even a strong tropical storm is capable of wind damage.

The intense eyewall winds of Category 5 Hurricane Andrew destroyed over 25,000 homes and damaged 101,000 more in Homestead and the south Miami suburbs in August 1992.

Despite that devastation, 26 deaths – 15 in South Florida – were directly attributed to Hurricane Andrew.

Of the 650 to 700 Atlantic tropical cyclones in the study's 50-year period, two to three systems were deadly in the U.S. each year on average.

Storm Surge: The Deadliest Threat

Roughly half of all U.S. deaths from tropical cyclones are due to the storm surge, the rise in water levels from the tropical cyclone's winds piling water toward the coast just before and during landfall.

Storm surge is not simply a function of the maximum winds. 

Hurricane Ike was not a "major" (Category 3 or stronger) hurricane at landfall in Galveston, Texas, in September 2008. Yet the size of Ike's wind field generated a 15- to 20-foot storm surge that wiped out most structures on the Bolivar Peninsula of Texas.

Well before the modern age of satellites, television and instant communication, a storm surge of up to 15 feet, with battering waves, claimed most of the 8,000 to 12,000 lives lost in the Galveston, Texas, 1900 hurricane, the nation's deadliest.

To more clearly communicate the threat from storm surge, the NHC will prepare potential storm-surge inundation maps when a hurricane or tropical storm threatens the coastline.

These maps will identify how deep the storm-surge inundation may be above ground level in a worst-case scenario based on the forecast track, intensity and wind field.

Before a hurricane threatens, find out if you live in an evacuation zone. Knowing this – and heeding evacuation orders from local emergency managers – could save your life and those of your family members.

Rainfall Flood Threat

There are two reasons for this.

First, a tropical cyclone's rainfall potential does not depend on its wind intensity, but rather its forward speed. The slower it moves, the more rain it can produce. Therefore, heavy rain can occur in the lion's share of tropical cyclones.

Secondly, the Rappaport study noted areas of heavy rain in tropical cyclones can occur far from the storm's center and well after the storm has fizzled as a tropical cyclone.

Hurricane Harvey in 2017 and Hurricane Florence in 2018 are two of the most recent examples of slow-moving hurricanes that caused disastrous flooding.

Hurricane Irene in 2011 may be one of the most forgotten U.S. landfalls, given Superstorm Sandy was just a year later.

There was surge flooding along the coast from the Outer Banks of North Carolina to southern New England, but this storm wasn't just a coastal danger.

Irene's legacy was its epic inland rainfall flooding from parts of New York state into New England, particularly in Vermont, where almost 2,400 roads, 800 homes and businesses and 300 bridges were destroyed or damaged from the flooding.

Of the 41 total U.S. deaths attributed to Irene, 21 of those were from rainfall flooding.

Now, consider a system that wasn't officially a depression anymore when it inflicted its havoc.

Tropical Storm Allison in June 2001 soaked the Houston metro area as it made landfall, then dropped a massive second deluge when its remnants moved southward back over the Texas coast a few days later. Up to 37 inches of rain swamped parts of America's fourth-largest city.

This $9 billion tropical storm, the costliest tropical storm in U.S. history, claimed 41 lives in the U.S. Twenty-seven of those died from rainfall flooding.

Hurricane Agnes in 1972 was barely so at landfall, a Category 1 when it crossed the Florida Panhandle coastline. However, its final move and subsequent stalling over the Northeast triggered massive flooding. Of the 122 U.S. deaths, 113 were due to rainfall flooding.

Did you know the infamous Hurricane Camille in 1969 also had a second deadly chapter in the Appalachians?

Flash floods and mudslides from 12 to 20 inches of rain claimed 113 lives in Virginia, almost as many as were killed from its Category 5 landfall.

The bottom line here is to respect the power of water in tropical cyclones. Don't become a statistic.

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