Upping its earlier prediction, the Colorado State University (CSU) hurricane forecast team, led by Phil Klotzbach and William Gray, said Tuesday the U.S. Atlantic basin will likely experience a very active hurricane season in 2007 with an increased probability of a major hurricane making U.S. landfall. The news surprised many within the energy industry who had expected that the team’s April forecast would simply be a rehash of its December 2006 outlook (see Daily GPI, March 29).
The team’s forecast now anticipates 17 named storms forming in the Atlantic Basin between June 1 and Nov. 30, with nine of the 17 storms expected to become hurricanes, and of those nine, five are expected to develop into intense or major hurricanes (Saffir/Simpson category 3-4-5) with sustained winds of 111 mph or greater. The team’s first extended-range forecast released in December anticipated 14 named storms forming in the Atlantic Basin between June 1 and Nov. 30, with seven of the 14 storms predicted to become hurricanes, and of those seven, three were expected to develop into intense or major hurricanes.
If the updated forecast sounds familiar, that is because it is. In last year’s April forecast for the 2006 Atlantic basin, the group forecasted the very same 17 named storms, nine hurricanes and five intense hurricanes (see Daily GPI, April 5, 2006). However, that forecast proved to be significantly off, which the team blamed on a late-developing El Nino and increased dryness in the tropical Atlantic (see Daily GPI, Nov. 20, 2006). The 2006 season actually witnessed a total of 10 named storms, five hurricanes and two major hurricanes, while the 2005 season, considered unusual by the Colorado State forecast team, witnessed 27 named storms, 15 hurricanes and seven intense hurricanes. Long-term averages are 9.6 named storms, 5.9 hurricanes and 2.3 intense hurricanes per year.
“We are calling for a very active hurricane season this year, but not as active as the 2004 and 2005 seasons,” said Klotzbach. “Based on our latest forecast, the probability of a major hurricane making landfall along the U.S. coastline is 74% compared with the last-century average of 52%.”
The team predicted that tropical cyclone activity in 2007 will be 185% of the average season. By comparison, 2005 witnessed activity that was about 275% of the average season.
“In December and January, we had a weak to moderate El Nino event in the tropical Pacific Ocean. When you have El Nino conditions during the hurricane season, it increases vertical wind shear across the tropical Atlantic and typically results in a weaker tropical cyclone season,” Klotzbach said. “However, we’ve seen El Nino conditions dissipate quite rapidly late this winter, so we do not think that’s going to be an inhibiting factor this year. Also, we have warm Atlantic sea surface temperatures this year, which we’ve seen just about every year since 1995.”
While some see El Nino an La Nina periods as good indicators of storm likelihood, others, such as AccuWeather.com’s Joe Bastardi, see it as a question of which came first, the chicken or the egg. “I believe the El Nino was the driven, not the driver of the pattern last year,” Bastardi said Tuesday as part of his running commentary on the 2007 storm season (see Daily GPI, April 3). “I believe there is entirely too much hype surrounding El Nino and La Nina. A strong La Nina is one that has been associated with storms staying south of the United States for one, and the years of most intensity in relation to our nation are many times not a La Nina. I, for one, am tired of everyone blaming the two for whatever goes on.”
Bastardi, who will release his 2007 Atlantic hurricane forecast in May, said if El Nino or La Nina events are strong and driven from other sources “(i.e., volcanic activity, then the corresponding turn back),” that is one thing. “However, this is getting entirely out of hand and is almost a disservice. You can’t, in one breath, blame El Nino last year for shutting the hurricane season down when the ’04 was a far stronger one in the heart of the season and wound up beating on the U.S. like a rented mule,” he said. “So unless they are overpowering my arguments, it is the larger scale [that] is more important. One of the more entertaining debates at our hurricane conference may be ME defending Bill and Phil’s raw forecast, if they are going to try to blame El Nino for causing the problem with their adjusted one.” The second annual AccuWeather Hurricane Summit will be held in Houston in early May.
Bastardi said the bottom line remains that the United States is currently in a time of climatic hardship where hot, dry summers in the West and Plains, and greater-than-normal hurricane activity on the coasts, is more the norm rather than the extreme. The forecaster added that while the Northeastern U.S. should be concerned about seeing hurricane activity in the years to come, Florida and the Gulf Coast should be especially nervous. ” I think ’04 and ’05 were ringing in a return to the ’40s,” said Bastardi. “The bottom line is this is a much more bullish forecast idea for threats to the energy of the U.S. than last year and also one where last year may be looked at as a breather.”
No hurricanes made landfall along the U.S. coastline in 2006, but the CSU team said there is an above-average chance that at least one will this year. The team’s probabilities include:
“We were quite fortunate last year in that we had no hurricane landfalls,” Klotzbach said. “The 2006 season was only the 12th year since 1945 that the United States witnessed no hurricane landfalls. Since then, we have had only two consecutive-year periods where there were no hurricane landfalls — 1981-1982 and 2000-2001.”
The team cautioned against reading too much into the hurricane seasons of 2004 and 2005 when Florida and the Gulf Coast were ravaged by four landfalling hurricanes each year. Hurricanes Charley, Frances, Ivan and Jeanne caused devastating damage in 2004 followed by Dennis, Katrina, Rita and Wilma in 2005.
“The activity of these two years was unusual, but within the natural bounds of hurricane variation,” said Gray, who began forecasting hurricane seasons at Colorado State 24 years ago. “Following the two very active seasons of 2004 and 2005, 2006 experienced slightly below-average activity with no landfalling hurricanes. We’ve had an upturn of major storms since 1995. We think this upturn of major storms will continue for another 15 or 20 years.”
Probabilities of tropical storm-force, hurricane-force and intense hurricane-force winds occurring at specific locations along the U.S. East and Gulf Coasts within a variety of time periods are listed on the forecast team’s Landfall Probability Web site. The site provides U.S. landfall probabilities for 11 regions, 55 sub-regions and 205 individual counties along the U.S. coastline from Brownsville, TX, to Eastport, ME. The website is available to the public at www.e-transit.org/hurricane.
The hurricane team’s forecasts are based on the premise that global oceanic and atmospheric conditions — such as El Nino, sea surface temperatures and sea level pressures — that preceded active or inactive hurricane seasons in the past provide meaningful information about similar trends in future seasons.
For 2007, Gray and the hurricane forecast team expect continued warm tropical and North Atlantic sea-surface temperatures, prevalent in most years since 1995, as well as neutral or weak La Nina conditions — a recipe for greatly enhanced Atlantic Basin hurricane activity. These factors are similar to conditions that occurred during the 1952, 1964, 1966, 1995 and 2003 seasons. The average of these five seasons had well above-average activity, and Klotzbach and Gray predict the 2007 season will have activity in line with the average of these five years.
Gray said he continues to see no relation to the changes in recent and projected Atlantic hurricane activity to human-induced global warming.
“Although global surface temperatures have increased over the last century and over the last 30 years, there is no reliable data available to indicate increased hurricane frequency or intensity in any of the globe’s seven tropical cyclone basins, except for the Atlantic over the past 12 years,” Gray said. “Meteorologists who study tropical cyclones have no valid physical theory as to why hurricane frequency or intensity would necessarily be altered significantly by small amounts of global mean temperature change.”
The team will issue seasonal updates of its 2007 Atlantic basin hurricane activity forecast on May 31, Aug. 3, Sept. 4 and Oct. 2. The August, September and October forecasts will include separate forecasts for each of those months.
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