Researchers Find Why Summer Hurricanes Hit at Levels Less Intense Than Forecast

By Erin Delmore

“Jersey Roots, Global Reach.” So says a sign at the Rutgers Coastal Ocean Observation Lab — the COOL lab, for short.

The lab’s work puts Jersey front and center. Researchers say they’ve figured out why experts have been mis-forecasting the intensity of summer hurricanes in our region.

“Hurricane track forecasts have really improved over the past 20 years, but the intensity forecasts of these hurricanes has lagged,” said Greg Seroka, PhD candidate for the Department of Marine and Coastal Sciences at Rutgers University.

Case in point: Hurricane Irene. The August 2011 storm wreaked havoc inland, but weakened to tropical storm status, falling short of expectations along the Jersey Coast. Why?

The researchers say it’s because that same warm water that draws us to the shore every summer sits on top of a cold bottom layer. A storm’s intensity mixes it all up so the water near the coast cools before the eye of the storm gets there. And since hurricanes are powered by warm water, this cooling leads to a less intense storm. Researchers say that pattern holds for every summer hurricane as it crossed mid-Atlantic coastal waters over the past three decades.

“The key is to have that two layer flow in the ocean so you have that increased shear force in mixing that friction in the ocean,” said Seroka.

“You don’t see that in, say, off of North Carolina or in the Gulf of Mexico, it’s not as typical conditions. So you can really only study this in places like off the coast of New Jersey. You can also study it off the coast of China in the Yellow Sea,” said Travis Miles, assistant research professor for the Department of Marine and Coastal Sciences at Rutgers University.

The team used NOAA’s offshore buoys, plus satellites and high-frequency radar systems, and what they call “underwater robots”.

Gliders, like the one here, measure ocean temperature, salinity and currents. The team at Rutgers deploys them all over the world, including a handful in New Jersey. They travel under storms to report data in real time, and their movements can be controlled remotely.

“There’s been a lot of research on hurricanes over the deeper ocean, where they form and how they propagate toward land, but we’re really the first to have the resources in the water underneath these storms on the coastal ocean,” said Miles.

Researchers say that when storm’s intensity is lower than originally forecast, the state wastes money and manpower on emergency preparedness. And people are desensitized. Some New Jerseyans didn’t heed warnings ahead of Superstorm Sandy figuring they weathered big, bad Irene just fine.

“We want people to have faith in the forecasts that are made so when emergency managers tell people to evacuate, they actually listen,” Miles said.

And so, this team is playing defense.

“A lot of the deep ocean research in hurricanes, we can think of them as the attack men, you know, going out and deploying floats, some gliders out in the deep ocean to go out in the storm, but we act as that goalie along the coastline, to protect that coastline,” Seroka said.

A job that will only get more important as sea levels rise and intense storms migrate northward.