In 2012 at least, McNoldy said, “That’s the exact opposite that has happened.’’
Hurricane Michael is the only storm that officially, and briefly, clocked in Cat 3 intensity during the six-month season. The hurricane center’s Landsea said Sandy, which struck Santiago de Cuba as a powerful Category 2 hurricane, potentially could be upgraded after annual post-season analysis.
But even if that happens, the percentage of storms making it to major status this season would remain unusually low. Typically, one of every four to five hurricanes reaches Cat 3 strength or higher at some point in its life.
Scientists can’t say for certain but a combination of factors may have contributed to tamping down intensity. A number of storms seemed to struggle with dryer than normal air, they say, thanks to a more stubborn and heavier influx of Saharan dust.
Wind shear also weakened some storms. That happened despite a predicted El Niño global weather pattern, which generally produces stronger shear and fewer storms, never kicking in. Many pre-season forecasts calling for an average or even below average number of storms had banked on El Niño to calm tropical development.
Instead, 2012 became the third straight year for the storm count hit 19, a total tied for the third busiest in records dating back to 1851. Ten storms became hurricanes, also above average. Only two years saw more storms: 1933 with 20 and 2005 with a stunning 28, including four that struck Florida in a six-week period.
But it was a season largely without strong hurricanes. By a broader measure called Accumulated Cycle Energy or ACE, a formula that weighs the duration and strength of storms, the season wound up a bit above average, ranking as the 11th most active in the last 30 years, Landsea said. That figure was bumped up a bit by never-say-die Hurricane Nadine, which formed, dissolved and reformed over nearly four weeks to become the fifth-longest enduring Atlantic storm on record. It was a nuisance only to the Azores off Africa.
Landsea called the recent high storm counts “somewhat misleading,” influenced by satellites and an array of technological advances that allow scientists to see and measure systems that likely would have gone undetected decades ago.
“We’re much better today at identifying weak, short-lived storms way out in the middle of the ocean,” he said.
Joyce, for instance, barely made it into a tropical storm and lasted two days. Florence was only a bit stronger and longer, hanging in for three days. Even Sandy, which spent days over warm waters that usually fuel development, struggled during its passage through the Caribbean, never managing to form a classic eye that defines monster hurricanes.
The year also produced a few other notable results.
South Florida, last struck by Hurricane Wilma in 2005, again dodged a couple of bullets. Hurricanes Isaac and Sandy both skirted the state. Downpour from Isaac caused serious flooding in spots, particularly in western Palm Beach County, but also largely erased a lingering regional drought. Sandy closed schools but the damage was mostly isolated to coastal flooding and sand blocking roads in Fort Lauderdale.
Though many pre-season forecasts predicted an average to below average year, the season also got off to a fast start. Tropical Storms Alberto and Beryl both developed before the official June 1 start of the season. Beryl, with 70 mph winds, hit Jacksonville in late May as the strongest pre-season hurricane on record. When Debby, a weak tropical storm formed in late June before drenching the Big Bend area of Florida, it marked the first time on record that four storms formed before July.