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Hurricane Irene: It’s the rain

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Precipitation is the underestimated, mundane, unexotic hazard of a tropical storm. No one fears rain. It is familiar, unlike a gale that gusts to 110 miles an hour or a sea that foams and rages.

But floods can be killers, their effects felt far inland. That fact was demonstrated this week as Irene, a hurricane that on paper had dwindled to a tropical storm, inundated the steep valleys of Vermont, the farmland of Upstate New York and many other places nowhere near the Atlantic Ocean.

“People aren’t scared of rain; they’re scared of wind,” said Kerry Emanuel, an MIT professor of atmospheric science who has studied hurricanes. “In most people’s minds, a hurricane is principally a wind event, and if they have heavy rain — it’s incidental, it’s too bad.”

The media generally think along the same lines, which is why hurricane coverage typically features a soggy, windblown weather reporter standing on a beach, shouting warnings of greater fury to come.

“Rainfall isn’t sexy. Everyone went to the coast looking for the wind and the storm surge,” said David Vallee, a National Weather Service hydrologist in Taunton, Mass.

Irene didn’t meet expectations of wind and storm surge, and some said the media had overhyped the storm. But losses from Irene will top $7 billion, according to an analysis cited by the Associated Press. Flooding affected a swath of the Eastern United States from New Jersey to northern New England, where 26 rivers set all-time high-water marks.

Irene proved especially rainy on its western flank, as tropical moisture from the south met colder air along the jet stream. The elevated terrain of the Catskills, the Berkshires and the Green Mountains helped wring moisture from the air as the storm raced to the north.

Vermont was primed for disaster. It had an especially snowy winter, with up to 200 inches recorded in some locations. It suffered floods in March and May. It had typical summer weather, but the soil remained wet, said Andy Nash, a National Weather Service meteorologist in Burlington, Vt.

Nash and his colleagues managed, with help from Vermont news media, to warn people that they were facing floods that would compare with the worst on record, back in 1927 and 1938. Vermont had recorded three flood-related deaths and a missing person as of Wednesday. Nash said that without the warnings, the death toll could have been higher.

Still, he said, a lot of people couldn’t imagine the scale of something like Irene, in which the entire state became inundated with six to eight inches of rain.

“Yes, a lot of people around knew about 1938 and 1927 floods, but until you’ve lived through it, I don’t think you have an appreciation for it,” Nash said. He posed a bigger question: “Do people really understand what Mother Nature is capable of?”

In New Jersey, the Raritan River swelled 13.9 feet above flood stage. In Vermont, the Winooski River surpassed flood stage by 10.2 feet. Similar figures could be found on the Mad River in Vermont, the Housatonic in Connecticut and the Pompton in New Jersey.

As of Wednesday, the Associated Press has tallied 45 deaths from Irene, at least a dozen from drowning. Many happened with stunning quickness as people encountered swollen creeks.

In Princeton, N.J., an emergency medical technician drowned in a creek while investigating a submerged car that turned out to be empty. A man in Wanaque, N.J., fell into a stream and drowned while going for a walk with friends after the storm had passed.

In New Scotland, N.Y., a woman was evacuating her home along the Onesquethaw Creek when she was swept away. In the Catskills, an 82-year-old Romanian-born Holocaust survivor died when her cabin was inundated by floodwater.

If there’s a single storm that Irene most resembled, in trajectory and impact, it may be Hurricane Floyd, from 1999. Floyd also tracked up the East Coast and, like Irene, proved less lethal than expected at the point of the spear. But its gravest impacts came days later, as floodwaters rose in North Carolina and adjacent states.

The underemphasis on precipitation doesn’t necessarily mean storm surge or wind are overhyped when hurricanes approach, said Hugh Willoughby, a Florida International University meteorologist. The most lethal hurricanes, such as Katrina in 2005 and Camille in 1969, tend to kill with storm surge, he said.

“If you kill hundreds of people, it’s almost always storm surge,” Willoughby said. But he said that most hurricanes don’t kill hundreds or even dozens of people.

“In the generic hurricane season, people drown in freshwater,” Willoughby said. “Season after season, it’s people drowning in freshwater flooding from torrential rains.”

A tragic example of hurricane-related freshwater drownings occurred when Hurricane Mitch struck Central America in 1998. Although Mitch had been a Category 5 storm, at landfall its winds were more modest. But the rainfall created flash floods that killed nearly 20,000 people, said Emanuel, the MIT professor.

Roughly half of those killed in U.S. hurricanes in the past 40 years have died in storm surges, and almost all of those fatalities were caused by Katrina, according to a recent study by Ed Rappaport, deputy director of the National Hurricane Center. Roughly one-quarter of the fatalities came from rainfall-induced flooding, he said. The rest were attributed to drowning in the surf and to wind-related incidents and tornadoes.

The key point is that every hurricane is different, and those differences are magnified by local conditions. How a hurricane will play out is something that no one can predict.

Vermont’s governor, Peter Shumlin (D), said Monday on the “Democracy Now!” radio program that climate change from the burning of fossil fuels is a factor in his state’s disaster. “We didn’t used to get weather patterns like this in Vermont,” he said.

Vermont and the rest of New England have, in fact, been pelted with many tropical storms over the decades. But Emanuel thinks Irene provides an illustration of what can be expected of such storms in a warming climate.

“Everything else being equal, hurricanes will rain more, just because they’re ingesting more water vapor,” Emanuel said.

Tom Peterson, chief scientist at the National Oceanic and Atmospheric Administration’s national climatic data center, said the damage caused by Irene should provide a warning: “Events like this routinely show us that we’re not adapted to the current climate, let alone to the future climate that we’re going to be having.”

Staff writer Jason Samenow and staff researcher Lucy Shackelford contributed to this report.

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