Hurricane Mathew tore through the Caribbean as a category four storm in October, 2016. But, it plummeted to a category one storm as it made its way to the eastern coast of the United States. This is a perfect example of something James Kossin, an atmospheric scientist with the National Oceanic and Atmospheric Administration, calls “an incredibly lucky phenomenon.”
Kossin is the author of a new study which evaluates hurricane activity from 1947 to 2015. While looking at this information, it was discovered that when conditions in the Atlantic favor increased hurricane activity, it creates a kind of buffer zone. This zone has the ability to weaken storms as they approach the coastal United States. “It’s given us a really nice barrier and decreased our threats,” says Kossin. This being said, the study also points out, when hurricane levels are low in the Atlantic there is a higher risk of stronger storms hitting the U.S.
The Atlantic meridional mode, a long-term pattern of high variability, can help scientists determine the strength of hurricane activity. In one phase, the mode shows warmer water on the surface of the tropical Atlantic and not much wind shear. These factors create the perfect environment for tropical storms like hurricanes to form. But, water conditions near the coastal United States show colder water surfaces and more wind shear. These kinds of conditions tend to tear the storms apart. This is where the buffer zone is created. The hurricanes form in the open ocean but by the time they the storms pass through the buffer zone, they are much less dangerous. When less hurricane activity is detected, these weather conditions switch, creating stronger storms near the coast.
Kossin found that during the most recent quiet period, from the late 1960’s up to the mid-‘90s, hurricanes that formed were up to six times more likely to become stronger by the time they hit the United States. For example, Hurricane Andrew, a category five storm that destroyed South Florida in 1992, occurred during the most recent quiet period and intensified rapidly as it came towards the United States.
Suzanna J. Camargo, a research professor at Lamont-Doherty Earth Observatory, says the study results are very “interesting”; however more research needs to be done before scientists can fully understand the findings.
New York Times