Milton’s massive storm surge has also highlighted the growing danger of the water. More intense hurricanes are causing greater storm surges due to rising sea levels. These “hurricanes on steroids,” as Olson calls them, are also dumping greater amounts of rain inland, just as Hurricane Helene did in North Carolina late last month. Between 2013 and 2022, flooding due to heavy rain accounted for a whopping 57 percent of hurricane deaths, and storm surge was responsible for another 11 percent. according to the National Hurricane Center. Wind caused only 12 percent.
The International Hurricane Research Center is known for its “wind wall,” a hangar of 12 giant yellow fans that can generate 157 mph winds to test the strength of building materials. It now has a $13 million federal grant to design and prototype a new facility with 200 mph fans and a 500-meter wave pool to test the effects of windier, wetter hurricanes.
“That’s the real world. There is not only wind, only water, only waves. You get all three,” Olson says.
Some meteorologists say we need a completely different scale. Carl Schreck, a research scientist at the University of North Carolina, has proposed a Category 1 to 5 scale based on sea level pressure to better incorporate water. Low pressure increases both wind speed and storm size, and larger storms tend to have larger waves and more rain. A Category 5 hurricane would be a hurricane with a pressure less than 925 millibars. By this measurement, Milton would have remained in Category 5 until mid-Wednesday instead of hovering between 4 and 5.
“Pressure is easier to measure, easier to forecast and is more important for damage, but the NHC, by inertia, is tied to the current system and believes that changing it would confuse people, unless there is a miracle solution” says Schreck. . “And there is no silver bullet.”
No number can capture all the impacts of hurricanes. This was demonstrated by Helene, which made landfall in Florida as a category 4 but unleashed “biblical” rains hundreds of miles inland in Georgia, South Carolina and North Carolina. the storm delicate More than 200 people, half of them in western North Carolina, where mountain valleys channeled rain into devastating floods. The impact was compounded by a tropical storm that showered the Carolinas with historic rain two days before Helene.
Before Helene hit, the forecasts compared its rains to hurricanes Frances and Iván, which brought Up to 18 inches of rain in parts of North Carolina in 2004, causing 400 landslides and killing 11 people. They also cited an unprecedented flood in 1916, warning that the “impacts will be life-threatening.” The storm two days before Helene broke described as a “once in a thousand years event.” But the fact that so many people died shows a “communication disconnect” between our storm warning system and the public, says Schreck, who lives in Asheville and was without power and water for days.
he has also helped develop an “enhanced rainfall” scale, where a Category 5 event dumps five times as much rain as an area would receive once every two years on average, a Category 4 event dumps four times as much, and so on. The predicted precipitation would have made Helene a Category 3 extreme precipitation event in the mountains of North Carolina rather than simply a Category 4 hurricane off the coast of Florida.