By Daniel Dunaief

In August of 2014, Islip experienced record rainfall, with over 13 inches coming down in a 24-hour stretch — more than the typical rainfall for an entire summer and a single day record for New York state. The rain required emergency rescues for motorists whose cars suddenly died after more than 5 inches of rain fell in a single hour.

What if, however, that rain had fallen just 50 miles west, in Manhattan, where the population density is much higher and where people travel to and from work on subways that can become flooded from storms that carry less precipitation?

Brian Colle, professor of atmospheric sciences and director of the Institute for Terrestrial and Planetary Atmospheres at the School of Marine and Atmospheric Sciences at Stony Brook University, is part of a group that is studying flood risks in the New York metro area during extreme storms that could bring heavy rains, storm surge or both. The team is exploring mitigation strategies that may help reduce flooding.

“The risk for an Islip event for somewhere in the NYC-Long Island area may be about one in 100 years (but this is being further quantified in this project), and this event illustrates that it is not a matter of whether it will occur in NYC, but a matter of when,” Colle explained in a recent interview.

The group, which is led by Brooklyn College, received $1.8 million in funding from New York City’s Department of Environmental Protection and the Mayor’s Office of Recovery & Resiliency. It also includes experts from The New School, the Stevens Institute of Technology and Colorado State University.

The co-principal investigators are Assistant Professor Brianne Smith and Professor Jennifer Cherrier, who are in the Department of Earth and Environmental Sciences at Brooklyn College–CUNY.

Smith, who had worked with Colle in the past, had recruited him to join this effort. They had “been wanting to do studies of flooding for New York City for a long time,” Smith said. “When the city came out with this” funding for research, Colle was “the first person I thought of.”

Malcolm Bowman, a distinguished service professor at Stony Brook University, holds his colleague, whom he has known for a dozen years, in high regard. Colle is “a leading meteorologist on regional weather patterns,” he wrote in an email. 

Colle is interested in the atmospheric processes that produce rainfall of 2 or 3 inches per hour. “It takes a unique part of the atmosphere to do that,” he said. The three main ingredients are lots of moisture, lift along a wind boundary, and an unstable atmosphere that allows air parcels, or a volume of air, to rise, condense and produce precipitation.

Representatives from the local airports, the subway systems and response units have been eager to get these predictions, so they can prepare mitigation efforts.

This group has taken an ambitious approach to understanding and predicting the course of future storms. Typically, scientists analyze storms using 100- to 200-kilometer grid spacing. In extreme rainfall events during coastal storms, scientists and city planners, however, need regional spacing of 20 kilometers. Looking at storms in finer detail may offer a more realistic assessment of local precipitation.

Researchers are anticipating more heavy rainfall events, akin to the one that recently caused flooding in Port Jefferson.

A warmer climate will create conditions for more heavy rains. Water vapor increases about 6 to 7 percent for every degree increase in Celsius. If the climate rises two to four degrees as expected by the end of the century, this would increase water vapor by 13 to 25 percent, Colle said.

The group includes experts from several disciplines. “Each of the scientists is highly aware of how integrative the research is,” Cherrier said. The researchers are asking, “How can we provide the best scientific foundation for the decisions” officials need to make. If, as predicted, the storms become more severe, there will be some “hard decisions to make.”

Smith suggested that a visible project led by women can encourage the next generation of students. Women undergraduates can appreciate the opportunity their female professors have to lead “cool projects,” she said. 

Raised from the time he was 4 in Ohio, Colle said he was a “typical weather geek” during his childhood. The blizzard of 1978 fascinated him. After moving to Long Island in 1999, Colle used to sit in a weather shed and collect ice crystals during nor’easters. He would study how the shape of these crystals changed during storms. An avid surf fisherman, Colle said there is “not a better place to observe weather” than standing near the water and fishing for striped bass, fluke, bluefish and false albacore. A resident of Mount Sinai, Colle lives with his wife Jennifer, their 16-year-old son Justin and their 13-year-old son Andrew.

As for his work on flood risks around the New York metro area, Colle said the group is producing monthly reports. The effort will end in December. “The urgency is definitely there,” he acknowledged. Heavy rainfall has increased the need to understand rain, particularly when combined with surge flooding.

A transportation study written over a decade ago describes storm surge and rainfall risk. That study, however, included a prediction of 1 to 2 inches of rainfall an hour, which is far less than the 5 inches an hour that hit Long Island in 2014.

“Once you start seeing that, there’s a lot of people who are nervous about that risk and want to get a best estimate of what could happen,” Colle said.

Cherrier described New York City as being “quite progressive” in gathering information and formulating data. “The city wants to be prepared as soon as possible.”