JACKSONVILLE, Fla. – Friday marks the official end of the 2018 hurricane season, and it will be remembered most for hurricanes Florence and Michael, which caused significant damage in the Carolinas and in the Florida Panhandle. In total, the season produced 15 named storms, including eight hurricanes of which two were “major” (Category 3, 4 or 5). An average season has 12 named storms, six hurricanes, and three major hurricanes, according to the National Oceanic and Atmospheric Administration.
The 2018 hurricane season was the first since 2008 to have four named storms -- Florence, Helene, Isaac and Joyce -- active at the same time. Hurricane Florence caused catastrophic flooding in parts of North and South Carolina. Several river locations in the Carolinas approached or broke their record flood level in the days and weeks following the hurricane. It took two to three weeks for many river locations to fall below flood stage, and the final river crested one month after Florence made landfall.
Storm-by-storm forecasts from NOAA’s National Hurricane Center were aided by the high-resolution imagery from NOAA’s new GOES-East satellite (GOES-16), and the American Global Forecast System (GFS) model, which produced accurate forecasts of landfall location and timing for both hurricane Florence and Michael. NOAA’s hurricane hunter aircraft flew more than 580 hours this season and provided valuable data in support of forecasting, research and emergency response.
Below are 4 factors that made the 2018 hurricane season unique and record-breaking:
Preseason storms
The 2018 hurricane season got off to an unusual start with a preseason storm forming well before the official start on June 1. On May 25, Subtropical Depression One formed in the northwest Caribbean.
According to NOAA, this system is one of just 21 other storms in recorded history to form before the beginning of hurricane season. Although a system forming before the start of hurricane season is statistically unusual, this was the fourth consecutive year it has occurred. After meandering towards the Gulf, it intensified into Subtropical Storm Alberto. Next, the subtropical storm transitioned into a tropical storm and plowed into the Panhandle on May 28. Alberto wasn't done with unique and record-breaking behavior after initial landfall either. The system maintained tropical depression strength all the way from Florida to Michigan before finally weakening into a remnant low. Michigan doesn't see many tropical depressions.
Record number of subtropical storms
The early start to the 2018 hurricane season also kicked off a record-breaking trend of subtropical storms. On average, we see 4 subtropical storms per year according to NOAA. A record seven named storms -- Alberto, Beryl, Debby, Ernesto, Joyce, Leslie and Oscar -- were classified as subtropical at some point. The previous record of five subtropical storms occurred in 1969. A subtropical storm is a named storm that has tropical and non-tropical characteristics. All subtropical storms this season eventually transitioned into tropical storms, with three -- Beryl, Leslie and Oscar -- eventually becoming hurricanes.
Unusual paths and landfalls
One of the two most destructive hurricanes this season, Florence, also had record-breaking and unusual behavior from the start.
The area in the Atlantic where Florence formed in early September is much farther north than where storms that make landfall in the U.S. form. According to NOAA, no tropical system in history has formed within 100 miles of that area and made landfall in the U.S. Instead of the typical path of a hurricane that curves, Florence's track across the Atlantic was almost a flat straight line.
We saw a never-seen-before landfall on the Iberian Peninsula near Portugal. Hurricane Leslie meandered in the northern Atlantic for two weeks before making its way towards Portugal as a post-tropical cyclone.
Tropical Storm Nadine formed Oct. 9 and its location just under 500 miles southwest of the Cabo Verde Islands made it the easternmost storm to ever form that late in the season.
Hurricane Michael
Hurricane Michael, at a Category 4 intensity, was the strongest hurricane on record to strike the Florida Panhandle.
It was the third-most intense hurricane to make landfall in the continental U.S. on record in terms of central pressure (919 mb) and the fourth-strongest in terms of maximum sustained winds (155 mph). Hurricane Micheal also showed unusually rapid intensification, growing from 35-mph winds to 155-mph winds in just over 72 hours.