The forecast for Superstorm Sandy was spot on. Two days before the storm struck the East Coast, meteorologists issued a strikingly accurate forecast of both the storm's track and strength. It gave emergency planners time to prepare. Residents time to get to safety.
It was a victory for meteorologists.
That's the storm you probably remember. But that's only part of the tale.
About five days before it made landfall in New Jersey, Sandy was barreling toward Cuba. Just a day out, forecasters predicted it would be a Category 1 hurricane with winds of about 80 mph.
By the time it hit, Sandy was a Category 3 with winds of 115 mph.
"That's a pretty big difference as far as impacts go," said Daniel Brown, a senior hurricane specialist with the National Hurricane Center.
They missed the hurricane's rapid strengthening.
The lesson is an old one: Forecasting hurricane intensity is an elusive challenge.
"It's the real rapid changes in strength up and down that we often have the most difficulty in forecasting," Brown said.
Though tremendous advances have been made in predicting hurricane tracks, little progress has been made in determining a storm's strength.
William M. Gray, a hurricane researcher at Colorado State University, agreed there are substantial issues with forecasting intensity.
"That's a real bottleneck," he said. "We've known we've had the problem for years. These storms are so complex."
Storm structures vary tremendously and numerous factors contribute to intensity.
"People who study these storms say each storm has its own personality,'' Gray said. "There's not one exactly like the other."
Bay News 9 chief meteorologist Mike Clay said meteorologists have struggled with predicting rapidly intensifying hurricanes since Andrew struck 21 years ago.
Forecasting intensity has been the subject of much research over the past decade. One improvement: measuring wind speed.
Andrew, which was upgraded from a Category 4 to Category 5 on its 10th anniversary, was bumped up in part because of data captured from a dropsonde, a device dropped from hurricane reconnaissance aircraft into the eye wall, measuring a variety of factors every 15 feet on its way down.
The dropsonde gives meteorologists a better look at the true strength of hurricanes, proving they had been underestimating speed of surface winds.