Hurricane Maria is the latest storm threatening to pummel the Caribbean as it batters Dominica and heads toward Puerto Rico. But what makes this Category 5 hurricane particularly dangerous, forecasters say, is its “dreaded pinhole eye,” which is much smaller than the eye of most hurricanes.

A Category 5 storm — the highest category on the Saffir-Simpson Hurricane Wind Scale — can be “life-threatening” and “potentially catastrophic,” according to the National Hurricane Center. However, Hurricane Maria’s drastically smaller eye could intensify the storm’s severity, increasing the risk that a region already weakened by a season of violent hurricanes will be completely devastated.

What is a pinhole eye?

The center of a hurricane, called the eye, is a uniquely calm area in a hurricane’s ring of storms. A typical hurricane develops an eye of 20 to 40 miles in diameter, but a pinhole eye is less than 12 miles wide.

In its advisory at 12 p.m. Eastern on Tuesday, the National Hurricane Center reported Hurricane Maria’s eye measuring only 8 to 10 miles in diameter.

To get an idea of the difference in size, here’s a very recent animation of Hurricane Maria, with its pinhole eye:

Hurricane Maria gaining speed
Hurricane Maria gains speed through Caribbean on Sept. 19.

For comparison, here’s an animated map of Hurricane Irma on September 9 as it moved over the Florida Keys.

Hurricane Irma approaching the Florida Keys on Sept. 9.

So what?

A smaller-than-normal eye is particularly catastrophic because it can cause a hurricane to gather more force and pick up higher wind speeds, according to the National Weather Service.

This effect is due to centrifugal force; when a hurricane’s wind is forced to spin around the eye in a tighter circle, the sharper curvature causes the wind to rotate faster, while the wind’s momentum wants to pull it in a straight line.

Just as riders on a playground carousel feel more pressure trying to push themselves off as the ride spins faster, the hurricane gains more force as it spins around its pinhole eye. That means Hurricane Maria could gain even more speed. As of Tuesday afternoon, it was sustaining maximum winds of 165 mph, which is well beyond the minimum wind speed of a Category 5 hurricane.

One of the most recent storms with a pinhole eye was [the brutal 2005 storm Hurricane Wilma, which resulted in 63 deaths and more than $29 billion of damage in Florida. The storm is still the most intense hurricane recorded in the Atlantic region, with its winds reaching 185 mph — more than Katrina, Sandy, or Ike.


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