Storm study started in 2011, after Hurricane Irene lost strength before making landfall in southern New Jersey. Findings could help forecasters make more accurate predictions. Watch video
In late August 2011, New Jersey was under a state of emergency and residents were evacuating towns along the Shore as Hurricane Irene was barreling up the Atlantic coast packing sustained winds as high as 85 mph.
But before the hurricane would make landfall near Atlantic City, it suddenly weakened. It still had the strength of a tropical storm when it landed in N.J. and ended up causing widespread damage and massive flooding, but its winds were not as intense as forecasters had predicted.
Researchers from Rutgers University have figured out what caused Hurricane Irene, pictured in this satellite image, to rapidly weaken before the storm made landfall in New Jersey in August 2011. (NASA)Researchers at Rutgers University say they have figured out why Irene -- and 10 other hurricanes that struck during summer months in the mid-Atlantic over a 30-year period -- weakened before making landfall.
The research team, led by Scott Glenn, a professor in Rutgers' Department of Marine and Coastal Sciences, discovered a high-energy process that rapidly cools the shallow stretch of ocean waters near the coastline and can knock down the strength of powerful hurricanes and tropical storms.
It's a process that had been seen in deeper ocean waters further out in the Atlantic, but never confirmed in coastal waters closer to land until now, the researchers said.
The study, published Tuesday in Nature Communications, says forecasts of hurricane tracks have improved steadily during the past two decades, but projections of hurricane intensity once they make land fall have been lagging.
"This is a missing piece required to close the intensity gap for land-falling mid-Atlantic hurricanes in summer," said Greg Seroka, one of the study's co-authors and a doctoral candidate in Rutgers' Department of Marine and Coastal Sciences.
Seroka and other researchers who worked on the five-year project say their findings could help forecasters improve the accuracy of their projections on how strong a hurricane or tropical storm will be before the storm slams into populated shorelines. Better accuracy, they say, could help reduce unnecessary preparation costs in cases where strong storms lose their intensity, and also reduce public skepticism over storm forecasts.
Why Irene weakened
Their study was launched in 2011 as Hurricane Irene was moving up the Atlantic Ocean. The researchers collected radar data, satellite images, wind and temperature readings from off-shore buoys, and information from an underwater glider -- a small submarine-like device that zig-zags around the ocean -- about 12 miles off the coast of Atlantic City.
The glider collects all sorts of important data, such as water temperature, salinity, and strength and direction of ocean currents, Seroka said in an interview Monday, and the data gets transmitted via satellite.
When examining Hurricane Irene, the researchers found that the strong winds on the leading edge of the storm churned up the Atlantic Ocean like a giant mixing bowl, causing the warm surface layer of the coastal waters to blend in with the much colder waters on the bottom layer, causing rapid cooling ahead of the hurricane's eye.
"The heat of the ocean is the energy driver for hurricanes," Seroka noted. When the ocean temperatures get cooler, the storms lose some of their energy.
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"Satellite imagery from before and after (Hurricane Irene) revealed that the ocean surface cooled up to 11 degrees Celsius, or 20 degrees Fahrenheit," said study co-author Oscar Schofield. With such a dramatic cooling, the researchers found, the hurricane quickly weakened before it would make landfall in southern New Jersey.
After studying Hurricane Irene, the Rutgers research team analyzed ocean data from 10 other major storms in the Atlantic between 1985 and 2015 and determined "the cooling occurred in every hurricane that crossed the mid-Atlantic coastal waters in summer," said Robert Forney, a Rutgers undergraduate who took part in the research project.
Members of the Rutgers hurricane research team, left to right: Josh Kohut, Scott Glenn, Oscar Schofield, Hugh Roarty, Greg Seroka and Travis Miles in the Rutgers University Coastal Ocean Observation Lab. (Nilsen Strandskov | Rutgers University) When the researchers went one step further, analyzing typhoons in Asia, they found extensive ocean cooling had occurred in 2011 as Typhoon Muifa crossed the Yellow Sea and then lost strength.
Other major storms in the Atlantic, such as Hurricane Floyd in 1999 and Hurricane Sandy in 2012, were not included in the Rutgers study because they did not occur during summer months, when coastal ocean temperatures are the warmest, Seroka said. Floyd formed in September, and Sandy struck in October, when ocean temperatures were already cool.
The study was funded by two federal agencies connected to the National Oceanic and Atmospheric Administration, as well as the U.S. Environmental Protection Agency, the New Jersey Department of Environmental Protection and the state Board of Public Utilities.
Len Melisurgo may be reached at LMelisurgo@njadvancemedia.com. Follow him on Twitter @LensReality. Find NJ.com on Facebook.