JACKSONVILLE, Fla – We have seen this unfold before, when out of a very quiet hurricane season develops a rapidly intensifying hurricane that barrels toward the mid-Atlantic U.S. east coast.
Researchers have noticed correlations between inactive hurricane season years that the strength of tropical cyclones close to the mid-Atlantic being stronger just the way Hurricane Florence is behaving.
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Hurricane Hugo was an example on September 22, 1989, when it made landfall on Sullivan's Island, South Carolina. Category 4 Hugo killed 27 people in South Carolina and caused $9.47 billion in damage. That was the nation's most expensive hurricane, although that record fell three years later when Hurricane Andrew struck South Florida.
As Hugo approached the coast, Jacksonville had 21 mph sustained winds, the highest in Florida. With Florence expected to be farther north at landfall, we will have no impacts from this storm locally other than large waves.
The fact both Hugo and Florence have rapidly strengthened to Category 4 hurricanes along the eastern seaboard in quiet years has caught the attention of hurricane researcher Jim Kossin.
His research looking at decades of hurricane activity shows coastal risk increases in periods generally considered unfavorable for hurricane formation.
Just like this year cooler water conditions and high shear over the Atlantic has lowered activity until September. Yet even with this months 3 hurricanes, this season seen lower average activity with just 9 named storms.
In less active years, hurricanes are two to three times more likely to rapidly intensify along the east coast during seasons with few storms.
Even when the overall weather conditions suppress the abundance of storms, the hurricanes that manage to overcome the hurdles are 3 to 6 times more likely to intensify into major approaching hurricanes.
Unfortunately, North Carolina is just days away from seeing another Hugo-like landfall with the troubling threat of days of Hurricane Harvey-like flooding long after the system make landfall in the Carolinas.