The U.S. appears to have a "buffer zone" near the coast that's protected the country from intense hurricane strikes over the past 20 years, according to a new study.
This protective barrier along both the East and Gulf Coasts, marked by strong crosswinds and cooler water temperatures, prevents hurricanes from intensifying as they near the U.S., the study said.
Counterintuitively, this buffer zone seems to be strongest during active hurricane eras, such as the one we've been in since the mid-1990s, said study lead author James Kossin of NOAA's National Centers for Environmental Information.
(The Atlantic Ocean switches between decades-long eras of busy and quiet hurricane activity.)
So when a hurricane that spins up during an active era approaches the U.S., it tends to weaken, the study said. An example of this was Hurricane Matthew last October, which weakened from a Category 4 near Haiti to a Category 1 as it neared the U.S.
"When conditions in the tropical Atlantic are good for hurricane intensification, they are bad for it near the coast,” Kossin said, who studied hurricane data from 1947 to 2015.
The barrier, or buffer, is formed by strong shearing winds and cooler ocean temperatures that set up along the coast, he said. The shear tends to tear hurricanes apart and cooler ocean temperatures don’t provide as much energy.
"This is remarkably fortuitous for residents along the U.S. coast," Kossin said. "The climate system provides extra protection from hurricane threats during periods when the basin-wide activity is at its greatest."
The period of high Atlantic hurricane activity over the past 20 years and development of the buffer zone may help explain the present “drought” of major hurricane landfalls in the U.S., which is now nearing 12 years. A major hurricane has winds of 111 mph.
The study also found that during eras of quiet hurricane activity, such as from the late '60s to the early '90s, the few storms that do spin up can intensify into monsters, such as Category 5 Hurricane Andrew in 1992, which smashed into south Florida.
WeatherBell meteorologist Ryan Maue, who was not involved in the study, said it was useful research: "We often hear from meteorologists and emergency planners and governors that 'it only takes one'" and 'don't let your guard down.' While a given season may be inactive or weak overall, there's a better chance that the one that does develop into a stronger hurricane will make it to the U.S. East Coast in a more intense state," Maue said.
Meteorologist Phil Klotzbach of Colorado State University, also not involved in the study, reviewed the paper, and said Kossin's results "make sense. All in all, I think this is an interesting study," he said.
Kossin said the protective buffer zone appears to only benefit the U.S., and not hurricane-prone areas of the Caribbean or Latin America.
The study, "Hurricane intensification along United States coast suppressed during active hurricane periods," was published Wednesday in the peer-reviewed British journal Nature.