Extremely Active 2017 Atlantic Hurricane Season Comes to a Close

The 2017 Atlantic Hurricane Season officially ends today.  Not only was it above average, as predicted, it was the basin’s fifth most active season on record.

According to NOAA, there were seventeen named storms this season. Of these, ten developed into hurricanes and six were major hurricanes with ratings of category 3 or higher on the Saffir-Simpson Scale. An average season produces twelve named storms, six hurricanes, and three major hurricanes. It is also interesting to note that this year’s ten hurricanes developed consecutively over the course of ten weeks, marking the largest number of hurricanes to form in a row in the satellite era.

This season’s Accumulated Cyclone Energy (ACE), which measures the intensity and duration of storms, was also exceptionally high. On average, a season will post an ACE of 104 in the Atlantic. This year, according to researchers at Colorado State University, it was 226 – the seventh highest in the historical record.

Officially running from June 1 to November 30, the season got off to an early start this year. Tropical Storm Arlene was a rare pre-season storm that developed in April. Another interesting outlier was Hurricane Ophelia in October. It was the easternmost major hurricane ever observed in the Atlantic Basin and the strongest storm on record to hit the Republic of Ireland. The biggest names of the season, however, were Harvey, Irma, and Maria.

In August, Harvey made landfall in Texas as category-4 hurricane. It was the first major hurricane to hit the United States since Wilma in 2005. It was also the wettest storm on record, dumping more than 50 inches of rain in southeastern Texas. This extreme precipitation caused catastrophic flooding in the Houston area.

Hurricane Irma maintained category-5 strength winds for 37 hours before making landfall as a category-4 storm in the Florida Keys. Measuring about 425 miles in diameter, Irma was wider than the Florida peninsula and its effects were felt across the entire Sunshine state in early September.

Just two weeks later, Hurricane Maria devastated Puerto Rico. It was the third category-four hurricane to hit the US, or one of its territories, in less than a month. In 166 years of record keeping, that never happened before.

Causing so much destruction, Harvey, Irma, and Maria will likely be retired from the World Meteorological Organization’s list of storm names.

This active hurricane season was largely the result of above-average sea surface temperatures in the Atlantic and ENSO neutral to cool La Niña conditions in the Pacific. With warm water to fuel storms coupled with reduced wind shear across the Gulf of Mexico, tropical development in the Atlantic basin was essentially unhindered.

In terms of economic impact, ENKI Operations, a private research firm, estimates the property damage, clean up costs, and lost business productivity from this year’s storms to be $206 billion. That would make 2017 the costliest hurricane season on record for the US. The official tally from NOAA will not be available until early 2018.

Data: NOAA