Back to Back Cats

In the last week, there have been several news stories about the recent island-wide power outage in Puerto Rico, the tenuous condition of Puerto Rico’s power grid, and the fact that hurricane season is right around the corner. Last Wednesday, a construction vehicle removing a fallen electrical tower got too close to an energized line and caused an electrical ground fault that led to an island-wide blackout. Luckily, power was not out across the island for long, but the outage once again drew attention to Puerto Rico’s efforts to rebuild following Hurricane Maria. Puerto Rico faced difficulties with its power grid even before Hurricane Maria made landfall, but Maria’s high winds and flooding damaged 75 percent of the island’s distribution lines. Despite the progress that has been made since Maria struck, it is clear that Puerto Rico has not fully recovered from Maria’s devastation.

We are on the eve of the Atlantic hurricane season, which runs from June 1 through November 30, with most storms occurring between August and October. But how much does Puerto Rico (and its neighbors) need to worry about another storm striking? We were curious how likely a hurricane season featuring back-to-back storms actually is.

It turns out that, despite Puerto Rico’s location in the stormy Caribbean, it is relatively rare for hurricanes to make landfall there, and the island experiences a tropical storm only every five years, on average. In fact, Maria was the strongest hurricane to strike Puerto Rico in more than 80 years, and just one Category 5 hurricane has made landfall in Puerto Rico since 1851—the San Felipe Segundo hurricane in 1928. Of course, given the tenuous state of Puerto Rico’s power grid, even a small storm could cause significant damage. As experts caution, it only takes one hurricane reaching land to result in an “active season.”

Hurricane patterns are difficult to predict, but some in the meteorological community forecast that 2018 will be an average or slightly above average Atlantic hurricane season. Researchers at Colorado State University predict 14 named tropical storms with 7 hurricanes, 3 of which are expected be “major” hurricanes (Category 3 or higher) with winds reaching at least 111 mph. That prediction includes a 52% probability that the Caribbean will see a major hurricane strike landfall; the probability for the U.S. coastline is 63 percent.

One of the more memorable back-to-back hurricane seasons in recent memory were the 2004/2005 seasons, which included Ivan, Katrina, Rita, Wilma, and at least three other hurricanes that struck the United States. In 2004, Hurricanes Charley, Frances, Ivan, and Jeanne struck Florida in a single six-week period. Ivan, in particular, caused extensive damage along the western Florida panhandle and drilling platforms in the Gulf of Mexico. Hurricane Jeanne, after devastating Haiti and leaving more than 3,000 people dead, made landfall in Florida in almost the same location as Hurricane Frances, ultimately causing $6.9 billion in damage in the United States. The very next year, in 2005, hurricanes Katrina, Wilma, and Rita devastated the gulf coast.

The continental United States was largely spared from Atlantic hurricanes for 12 years, but, as we know, 2017 was a record-setting and devastating year for hurricanes in the U.S. and Caribbean. In 2017, the United States experienced three Category 4 landfalls in a period of 26 days: Harvey, Irma, and Maria. The previous three occurred over a period of 56 years. Harvey, Irma, and Maria were three of the top five costliest storms on record, according to the National Hurricane Center.  Hurricane Katrina (2005) is the costliest U.S. hurricane on record, followed by Hurricane Harvey (2017), Hurricane Maria (2017), Hurricane Sandy (2012), and Hurricane Irma (2017) in fifth place. Hurricane Harvey struck Texas and other parts of the Gulf coast, causing an estimated $125 billion in damage. Just one week after Harvey, Irma devastated parts of the Caribbean before heading for Florida, where it caused extensive flooding, storm surges, power outages, and the deaths of 69 people and billions of dollars in damage. The National Hurricane Center classifies Irma as one of the strongest and costliest storms ever recorded in the Atlantic Ocean. Not to be deterred, Hurricane Maria struck Puerto Rico and the U.S. Virgin Islands weeks later, and became the costliest hurricane on record to strike those islands.

Posted by Laura Bartlow