Each spring, as predictable as rain, meteorologists make a splash in the news with their seasonal hurricane forecasts. Pioneered in the 1980s by Dr. William Gray, the annual prognostications have come under scrutiny because two of the last few years did not pan out as predicted.

Even meteorologists disagree on the value of seasonal forecasts, mainly because there are so many remaining unknowns when it comes to anything as unpredictable as hurricanes. Early on, landfall cannot be predicted and track and intensity forecasting are far from accurate. Boat owners may hear news about an "above average" year, but are not sure what that really means. Consider the fact that Hurricane Andrew devastated South Florida in 1992 – in a "below average" hurricane year. And in 1983, Hurricane Alicia struck Houston/Galveston, TX, in another below-average year.

"If you go back over the last 100 years you can find years during a quiet period when it was a very active year," said Chief Meteorologist Steve Letro with the National Weather Service in Jacksonville, FL, and a liaison to the National Hurricane Center in Miami. "There are lots of smaller things going on within those cycles. In 1992 there were only four hurricanes – but one of them was Andrew."

Letro agrees that perhaps too much is made of the annual pre-season forecasts, but overall the analysis of global weather patterns each year and the comparison to actual results at the end of the season are worthwhile research efforts. For the scientific community, he says that the "humility factor" is also helpful in reminding us how much we still do not understand about the complexity of global weather systems. "We find out that we need to know more than we thought we did," he said.

For the general public, the early season forecasts mainly serve as a wake-up call that it’s time to make a hurricane plan or update last year’s plan.THE MULTI-DECADAL SIGNAL

Dr. Gerry Bell, the lead forecaster at the National Climate Prediction Center in Camp Springs, MD, maintains that forecasts serve a number of purposes. The center is a department within the National Oceanic and Atmospheric Administration (NOAA) but separate from the National Hurricane Center and the National Weather Service.

"The scientific basis is very strong for these forecasts," he said. "There are a number of dominant climate patterns that favor more hurricanes. We're seeing conditions very much like 1995, which began this more active period."

Scientists agree that a pattern of conditions, referred to as the "multi-decadal signal" began in 1995 and could continue for 25 to 40 years. The last period was in the 1950s and 1960s, then the conditions switched to a less active period in the 1970s, '80s and early '90s. "NOAA's research shows that the multi-decadal signal is the major player in hurricane formation," Bell said.

The hallmarks of the multi-decadal signal are: convection patterns in West Africa and the Amazon Basin, and wind patterns driven by above-normal sea surface temperatures in the Atlantic Ocean. The "wild cards" in all this are the possible developments of either El Niño or La Niña, ocean conditions in the eastern Pacific that can either enhance hurricane formation (La Niña) or douse them (El Niño). The warming or cooling of ocean waters is difficult to predict but La Niña appears to be waning for this year, as of press time. El Niño can suppress hurricane formation but there were no signs of one by mid-July. Since the hurricane season lasts from June 1 through November 30, a lot can change in a few months time.

"Winds really control whether you're going to have an active season or not," Bell said. "That being said, where and when a hurricane will make landfall is an entirely different question, influenced by weather that cannot be predicted beyond a seven-day period."

MAKING PREDICTIONS

The forecast by NOAA for last year's hurricane season was very close to that of forecaster Dr. William Gray of the Colorado State University Dept. of Atmospheric Science in Fort Collins, CO. However instead of a fixed number, which Gray forecast, NOAA gave a range and a probability. For 2008, NOAA forecast that there was a 65 percent probability that it would be an above-average year for hurricane activity, with 12-16 named storms, six to nine becoming hurricanes and two to five becoming major hurricanes (Categories 3, 4 or 5).

How did it pan out? NOAA, for its part, was pretty much on target, forecasting another above-average year of hurricanes,

For the first time since records were kept, the U.S. Mainland was hit by six consecutive hurricanes. The Atlantic basin season, which ended November 30, produced 16 named storms and was the fourth most active season in 64 years. Eight named storms became hurricanes and five intensified ito Category 3 or larger hurricanes. Making landfall in the U.S. were hurricanes Dolly, Edouard, Fay, Gustav, Hanna, and Ike, which dealt a serious blow to Houston-Galveston causing the most damage to boats seen in years.

"My reading of the general public is that they know you can't forecast any season all that well but they still, before the season, want to know what the odds are and how the atmospheric and ocean conditions are lining up," said Dr. Gray in an early season podcast.

"We do have the skills with multi-year forecasts . . . The public has a great curiosity and we should tell them."

Boat owners in hurricane-prone areas may recall that 2006 and 2007 also predicted to be above-average seasons, were relatively quiet – no Charleys, Wilmas, Ritas or Katrinas. But were they really? As they say, all weather, like politics, is local.

"If a forecast fails, it's due to the fact that Atlantic and Pacific conditions didn't play out as expected," said Dr. Phillip J. Klotzbach who is now the lead forecaster for the Colorado forecasts. "For example, in 2006 no one predicted El Niño to come on. If we'd known that earlier we would have predicted less storms.

For the first time since records were kept, in 2008 the US mainland was hit by six consecutive hurricanes."The same thing occurred [in 2007] when we had a big trough [low pressure area] in the middle of the Atlantic that developed in September and just stayed there, shearing apart all the storms trying to form," Klotzbach said.

For those living in Central America, 2007 was anything but quiet. Two rare Category 5 hurricanes formed last year: Hurricane Dean hit the Yucatan Peninsula Aug. 21 with 175 mph sustained winds; and Hurricane Felix devastated part of Honduras and Nicaragua Sept. 2 with 160-mph sustained winds. Those countries sustained billions in damage and 174 deaths from the two events.

In fact, 2007 was actually a very active year with 15 named storms, and six hurricanes, two of them major (see map). NOAA forecast 2007 would have 13-17 named storms, 7-10 hurricanes, 3-5 of them major. But because only one hurricane (Humberto, Sept. 12-14), one tropical storm and three tropical depressions came ashore in the U.S.,

Americans thought the season was "ho-hum" and predictions were off. "The U.S. caught a bit of a break," said Bell. Much of the cutting edge research is aimed at improving track forecasting and intensity forecasting, two difficult equations in the hurricane package. NOAA and NASA have been conducting research in West Africa where storms are first born and become tropical waves in the Atlantic, called Cape Verde storms. These waves produce 60 percent of all Atlantic named storms.

NOAA is also beginning the use of low-altitude unmanned aircraft flying into the eyes of tropical storms in another effort to improve intensity forecasting One researcher said intensity forecasting is about 15-20 years behind track forecasting, which meteorologists have improved by 1-2 percent each year. Even still, the amount of track error is now about 75 miles from what is forecast 24 hours before a storm hits.

THE GREATER GOOD

While hurricane forecasting feeds the public's fascination with extreme weather, experts say the information is of great value to a host of groups, including insurers, emergency planners, agriculture, government agencies and the like. For the general public, the early season forecasts mainly serve as a wake-up call that it's time to make a hurricane plan or update last year's plan.

"It gives agencies a heads up of what they can expect and there is a lot of information there that these people can use. But for the individual, this is their cue to start preparing," said Bell.

"People should not be complacent about a hurricane season; coastal residents need to prepare each and every year to mitigate their risks," said Bell. "Regardless of the seasonal outlook, all it takes is one.

THE WEATHER UNDERGROUND