As hurricane season winds to a close, this year may well be remembered for what didn't happen:
• Only two hurricanes have formed, with no impact on the United States.
• Neither of them were major hurricanes, with winds of 111 mph or more.
• Tropical activity has been a third of normal in the Atlantic Ocean, Caribbean Sea and Gulf of Mexico.
"It's been one of those years that keeps you humble,'' said hurricane forecaster Phil Klotzbach of Colorado State University.
Most forecasters expect little activity in the final six weeks of the season, though they offer the usual caveats.
"We are definitely winding down, and it is looking less likely that we will have something major, but the probability is not zero,'' said Stacy Stewart, senior hurricane specialist with the National Hurricane Center in Miami.
It has been the quietest hurricane season since 1994, when only seven storms formed. Experts disagree about the exact starting point, but that was about the beginning of the current above-average era of hurricanes, expected to run at least 25 years.
Hurricane forecasters this year predicted an average of about 17 storms, with half of them becoming hurricanes and four or five of those becoming major hurricanes. So far this year we have had 11 storms, two of which briefly developed into hurricanes.
Many predictors are describing this season as a "forecast bust.''
''We don't forecast as well as we think we do,'' said George Sambataro, chief meteorologist with PC weather products, which specializes in hurricane tracking and analysis.
Part of the downturn can be traced to a massive cloud of dry air that moved into the traditional hurricane breeding ground in the middle of the season.
Tropical storms, powered by warm water, can quickly destabilize or deteriorate when infused with dry air. But other factors also played a role, including high wind shear in parts of the Atlantic, Caribbean and Gulf of Mexico, particularly at latitudes where several storms tried to form, said Stewart, the hurricane center specialist.
Experts say unforeseen factors can dramatically alter a forecast, underscoring the complexity of the atmosphere.
"Let's say eight of the 10 things we look at indicate a busy season,'' said Klotzbach, who, along with Bill Gray, issues one of the primary annual forecasts. "But every once in a while you get a year like this, when the other two factors swamp everything else.''
As evidence of the season's anomaly, experts point to the accumulated cyclonic energy, a measure of the total amount of tropical activity in a given area.
This season, the Atlantic basin had less than a third of accumulated energy it normally would generate. If forecasters are accurate, the season will end with less than a fourth of the norm.
But it's not over yet. In fact, one computer model foresees a tropical storm in the Caribbean later this month or early in November.
"The Caribbean waters are still warm, and we could have something pop up there,'' said Klotzbach, "but right now it does not look likely.''
Forecasters warn that the final weeks of the season should get particular attention from west Florida residents. "We've been hit more in late October than any other time, historically," said Mike Clay, chief meteorologist for Bay News 9. "I always say that in the tropics, you take it four or five days at a time."