The below-average number of hurricanes this year highlights the uncertainties in near-term forecasts, a catastrophe modeling firm warned in its latest report.

Boston-based AIR Worldwide said the low number of storms in 2006 may be explained by a mild El Ni?o event and the effects of dry air from Africa.

In a study titled "The 2006 Hurricane Season In Review," AIR also said that the milder-than-expected 2006 season won't prompt much of a change in its view of hurricane risk.

AIR added that the gap will shrink between hurricane frequencies in its near-term model--introduced last year--and AIR's "standard model," which is based on 100 years of hurricane data.

"Preliminary results of our current research indicate that the difference in mean hurricane frequency between the near-term sensitivity catalog and our standard model will not be as large as in 2006," the report said.

AIR management, including Chief Executive Officer Karen Clark, interviewed earlier this year, have repeatedly said that insurers and reinsurers should understand the considerable uncertainty associated with any near-term view of hurricane activity when applying it to critical business decisions.

"A single season, or even two consecutive seasons, should not radically change our view of the risk," the new report said, echoing comments included in an AIR white paper released last spring.

"The 2006 hurricane season confirms that the uncertainties in near-term forecasts are considerable," the report said, explaining that even when sea surface temperatures in the Atlantic are warmer than average for most or all of the season--a factor that forecasters thought would lead to higher-than-average hurricane activity this year--other climate factors can come into play.

One example occurred in October with the onset of a moderate El Ni?o event, the report said, noting that while El Ni?o conditions produce elevated sea temperatures in the Pacific, they translate to increased wind shear in the Atlantic.

While not affecting sea surface temperatures, the less-well understood effects of the Saharan Air Layer also played a role this year, AIR reported.

The firm's analysis explains that storms over Africa's Sahara Desert can carry significant amounts of dry, dusty air westward over the Atlantic Ocean, depriving tropical cyclones of the moisture and heat they need to mature.

The report, available on AIR's Web site at www.air-worldwide.com, also reviews the hurricane predictions of major forecasting groups made from April through October, comparing them with actual activity this year. One of the earliest and worst forecasts, from Colorado State University, overshot the year's actual total of nine named storms by eight, predicting a total of 17 in April.

Special Reports /

'06 Shows Hurricane Forecast Defects: AIR

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