Joining the ranks of other experts such as Colorado State University (CSU) forecasters William Gray and Philip Klotzbach who have been recently slashing their 2006 Atlantic hurricane activity predictions, Andover, MA-based WSI Corp. downgraded its outlook last week for the second time in two months. WSI said it now expects the tropical season to have 13 named storms, six hurricanes and three intense hurricanes (Category 3 or greater).

WSI pointed out that while these numbers are still larger than the long-term averages of 9.6 named storms, 5.9 hurricanes and 2.3 intense hurricanes, they are much smaller than last year’s record numbers. The devastating 2005 season witnessed 27 named storms, 15 hurricanes and seven intense hurricanes. As of the Minerals Management Service’s final report June 19, 2006, a total of 935.7 MMcf/d of Gulf of Mexico natural gas production was still off-line because of damage caused by hurricanes Katrina, Rita and Wilma in 2005. Since Aug. 26, 2005, a total of 803.6 Bcf of natural gas production has been deferred due to the storms, which equates to just over 22% of the annual gas production from the Gulf (3.65 Tcf).

WSI said its new forecast is “slightly” lower than the company’s original May outlook of 15 named storms, nine hurricanes and five intense hurricanes (see NGI, June 5), and its July update of 14 named storms, seven hurricanes and four intense hurricanes.

“While we still expect a relatively active year compared to long-term averages, it appears that conditions are in no way similar to last year’s record season,” said WSI seasonal forecaster Todd Crawford. “Prodigious amounts of Saharan dust over the tropical Atlantic, along with stronger-than-normal westerly shear, appear to be suppressing tropical development this year. On the other hand, tropical Atlantic Ocean temperatures are warmer than normal, so we do feel like the season will still run slightly above long-term averages.”

Earlier this month, CSU’s Gray and Klotzbach said they now expect there to be fewer hurricanes in the Atlantic in 2006 than during a normal season. Based on changing climate signals and below-average activity in the first third of the season, the CSU team is now calling for a total of 13 named storms to form in the Atlantic basin this season. Of these, five are predicted to become hurricanes and two are anticipated to evolve into intense hurricanes (Saffir/Simpson Scale Categories 3-4-5) with sustained winds of 111 mph or greater. The new forecast is down from the team’s already revised August forecast of 15 named storms, seven hurricanes and three intense hurricanes (see NGI, Aug. 7).

“We predict September and October will exhibit characteristics of a more average year based on the activity so far this season and climate signals through August,” Klotzbach said. “Current conditions in the Atlantic indicate that we will now see a slightly below-average hurricane season with far less activity than was experienced in each of the last two years.”

These changes include drier tropical Atlantic mid-level moisture fields, high levels of West African dust over the Atlantic, and a warmer eastern equatorial Pacific, indicating a potential El Nino event this fall. Gray and Klotzbach said that unlike 2005 when two major hurricanes — Dennis and Emily — developed and intensified in the tropical Atlantic and Caribbean, no hurricane activity occurred in the deep tropics during June and July 2006. August 2006 had about average named-storm activity, but the amount of intense activity was well below-average. Only one hurricane — Ernesto — formed during August — and lasted less than one day due to interaction with land. On average, about six hurricane days occur during August.

Looking at the next two months, the CSU team said the September-only forecast calls for five named storms, three hurricanes and two major hurricanes, which is slightly above-average for September. The October-only forecast calls for two named storms, one hurricane and no major hurricanes, which is below average. “Despite the lower predictions, residents living along the U.S. coastline should always be prepared for major storms,” Gray said.

Until 2004 and 2005, Gray and Klotzbach said the United States has been fortunate over the past few decades in experiencing only a few major hurricanes making U.S. landfall. Between 1995 and 2003, 122 named storms, 69 hurricanes and 32 major hurricanes formed in the Atlantic basin. During that period, only three of the 32 major hurricanes — Opal, Bret and Fran — crossed the U.S. coastline. Based on historical averages, about one in three major hurricanes that forms in the Atlantic basin comes ashore in the United States. But in the past two years, 13 major hurricanes formed in the Atlantic basin — seven of them striking the U.S. coast, the CSU team said.

“For many years, we have been warning of the return of major hurricane landfall events similar to what was experienced in the 1940s through the 1960s,” Klotzbach said. “We also warned that destruction was likely to be higher than was previously experienced due to increased coastal population and wealth per capita.”

“We recommend that there not be too much read into the last two hurricane seasons of 2004-2005,” Gray said. “The activity of these two years was unusual but well within natural bounds of hurricane variation. This is how nature sometimes works.”

The CSU team said it will issue a seasonal update and an updated monthly forecast for October 2006 Atlantic basin hurricane activity on Oct. 3.

As of last week, the National Oceanic and Atmospheric Administration (NOAA) was still sticking with its revised August forecast of 12 to 15 named storms — of which seven to nine are expected to intensify to hurricanes, including three or four becoming major hurricanes (see NGI, Aug. 14). In late May (see NGI, May 29), NOAA predicted 13 to 16 named storms, with eight to 10 becoming hurricanes, of which four to six could become major hurricanes.

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