It's been a busy, wet hurricane season

Two hurricanes whirled far off in the Atlantic Ocean on Thursday, with one of them, Michael, briefly strengthening into this year’s first major storm.

Along the Gulf Coast, a sloppy offshoot of Hurricane Isaac has an outside shot at becoming Nadine, the 14th named storm of the season. But even if what forecasters have dubbed the “spawn of Isaac’’ doesn’t develop into a full-fledged storm, it could bring more rain to already flooded coastal Louisiana or possibly North or Central Florida, where it could add to the runoff still filling up Lake Okeechobee, which has risen two feet since Isaac’s passage nearly two weeks ago.

Hurricane season doesn’t officially reach its historical peak and halfway mark until Monday but 2012 has already proved more active than many experts expected — particularly when measured by the number of storms. Most pre-season forecasts called for an average year with nine to 15 named storms, including four to eight hurricanes. The total so far: 13 storms, seven reaching hurricane strength.

“It’s been a very strange year,’’ said Phil Klotzbach, a research scientist at Colorado State University who teams with climatologist William Gray to produce pre-season forecasts. Alberto popped up just off South Carolina. Chris and Ernesto hit hurricane strength for less than a day. Tropical Storm Florence quickly dissolved into a tropical wave. Hurricanes Lesley and Michael gelled farther north than is typical and never posed a threat to the mainland U.S.

“It’s been active but active in strange places,” said Klotzbach.

By one key measure combining the duration and strength of each storm, 2012 is running about 140 to 150 percent above average, said Brian McNoldy, a senior research associate at the University of Miami’s Rosenstiel School of Marine & Atmospheric Science.

But it has generated only one storm above Category 3 strength — Michael got there briefly but then weakened — and the season has fortunately come nowhere close to matching the intensity of 2005, which spit out a record 28 storms, including Katrina and several storms that spent at least some time at Category 5 strength.

McNoldy said a combination of dry air and stronger than expected wind shear in the tropics have helped keep storms relatively tame — at least so far. Late season storms often prove more powerful but a slowly forming El Niño weather pattern expected sometime this month could help slow down the so-far busy season.

El Niño, marked by warming Pacific Ocean temperatures, typically fuels upper-level winds in the Atlantic that can weaken forming storms or sometimes rip them apart.

“I don’t think we’re going to see any crazy surge in activity,’’ said McNoldy.

Water managers in South Florida, still watching Lake Okeechobee rise from Isaac runoff and heavy rains over the last few days, are hoping for a dry spell.

Isaac pretty much erased concerns of a water shortage in South Florida, flooding portions of western Palm Beach County and the drenching the Kissimmee River basin, which flows south into the lake. Steady rains over the last few days have added to the inflow, said Randy Smith, a spokesman for the South Florida Water Management District, pushing the lake level to 14.42 feet above sea level — right at its historic seasonal average.

But if Isaac’s remnant drifts across Central Florida in coming days, it could potentially bring more runoff south, pushing the lake to a level that could begin to raise safety concerns about its aging dike, slowly being upgraded by the U.S. Army Corps of Engineers.

Under a management plan the Corps adopted in 2008 intended to balance water supply demands with environmental protection, the goal is to keep the lake’s water between 12.5 feet and 15.5 feet above sea level, with the peak coming at the end of the wet and hurricane seasons. After the 2004 and 2005 hurricane seasons, the Corps was forced to dump massive volumes of lake water to protect the dike, but the polluted runoff ravaged estuaries on both coasts, killing fish and triggering algae blooms.

John Campbell, a spokesman for the Corps, said the agency was closely monitoring weather reports but there had not yet been any discussion about releasing water from the lake.