Sandy ends hurricane season on forceful note

• There were 19 named tropical storms and hurricanes
• Sandy didn't hit the U.S. as a hurricane
• Sandy's winds spanned 943 miles of the U.S. coast

Roaring ashore with the power of five atomic bombs, monstrous Hurricane Sandy — and the superstorm it morphed into — shattered what had been an unremarkable hurricane season until late October.

Besides Sandy, which technically didn't hit land as a hurricane, the only hurricane to hit the USA this year was Isaac, which ravaged southeastern Louisiana in August, killing seven people.

The 2012 Atlantic hurricane season officially ends Nov. 30, but the season is likely over. Only five hurricanes have hit the USA in November in the past 162 years, according to data from the National Hurricane Center. And "there's nothing out there now," hurricane center spokesman Dennis Feltgen said.

For the Atlantic season, there were 19 named tropical storms and hurricanes, well above the long-term average of 12. Of the 19 named storms, 10 became hurricanes. A tropical storm becomes a hurricane when its sustained winds reach 74 mph.

Preseason predictions from Colorado State University said 13 named storms would form (of which five would be hurricanes), while the National Oceanic and Atmospheric Administration predicted nine to 15 named storms, of which four to eight would be hurricanes.

Colorado State's forecasting team has been making annual hurricane season predictions the longest, since 1984.

"It was a very unusual year," says meteorologist Phil Klotzbach of Colorado State University, due to the fact that so many storms formed, though many were fairly short-lived and on the weak side.

Amazingly, Neither Sandy nor Isaac reached "major" hurricane status — which is a hurricane that reaches Category 3 on the Saffir-Simpson Scale of Hurricane Intensity, winds of at least 111 mph. Only forgettable Hurricane Michael in September reached Category 3 status, and that was for only a few hours out in the open Atlantic Ocean.

"Nobody would have forecast a season like this," Klotzbach says, citing the fact that only one of the 10 hurricanes that formed was "major."

One factor in the unexpectedly large number of storms was the failure of the long-predicted El Nino to develop, he added. El Nino is a warming of tropical Pacific Ocean water that tends to suppress hurricane activity in the Atlantic basin.

Although it had been predicted to form toward the middle and end of the season, it never developed and isn't likely to this winter, according to a recent forecast from the Climate Prediction Center.

The season started vigorously, with four named storms in May and June, the first time that had happened since record-keeping began in 1851. After July, when there were no storms, eight developed in August, tying a record set in 2004.

Isaac hit in Louisiana on Aug. 28 with 80-mph winds and caused $2 billion in damage.

Only two storms formed in September, typically the most active month, neither of which hit the USA.

All of this was mere prologue for the ferocity of Sandy, which killed 121 people in the USA (199 overall) and caused an estimated $50 billion in damage, the second costliest natural disaster in U.S. history after Hurricane Katrina in 2005.

Sandy officially made landfall near Atlantic City, N.J., but not as a hurricane. "It will not go into the books as a landfalling hurricane," says Feltgen. He said it hit as what's called a "post-tropical cyclone," since it was transitioning into a hybrid storm as it neared land, one that meteorologists will be studying for decades.

At landfall, Sandy's tropical storm-force winds spanned 943 miles of the U.S. coast, according to Weather Underground meteorologist Jeff Masters, who said that no hurricane on record has been wider.

One measurement of a hurricane season's activity is what scientists call "Accumulated Cyclone Energy," or ACE. According to the hurricane center, ACE is an index that combines the number of systems, how long they existed, and how intense they became.

The ACE so far this year is 129, Klotzbach reported. An average year has an ACE of 92. The worst year on record was 2005, which had an ACE of 248. The 2005 hurricane season included Hurricanes Katrina, Rita and Wilma.

As for the Eastern Pacific hurricane season, it was on the active side, Feltgen said, with 17 named storms, of which 10 were hurricanes.

An average Eastern Pacific hurricane season produces 15 named storms, with eight becoming hurricanes, NOAA reports.