Upping its earlier prediction, the Colorado State University (CSU) hurricane forecast team, led by Phil Klotzbach and William Gray, said last week 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 NGI, April 2).

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 NGI, April 10, 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 NGI, 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 and La Nina periods as good indicators of storm likelihood, others, such as AccuWeather.com Hurricane Center Chief Forecaster 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 last week as part of his running commentary on the 2007 storm season. “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.”

Bastardi said people should pay much more attention to the forecasted storm intensity than the much more publicized number of storms expected for a season. With that being the case, he warned that close attention should be paid to the 2007 season.

“The overall numbers are a red herring in the forecast for the amount of impact on the United States. If one looks at the ’33-’38 seasons, the two most intense hurricanes in what is a very similar period in the AMO [Atlantic Multidecadal Oscillation], the early to midperiod of warming hit in relatively down years,” he said. “In addition, there was no strong El Nino or La Nina signal in any of those years. The point is that the most legendary U.S. and Northeast hurricanes were the 1935 Labor Day Storm and the 1938 Long Island Express. The shift of the QBO [quasi-biennial oscillation] to westerly means the greater threat for stronger storms than last year.” The QBO is a quasi-periodic oscillation of the equatorial zonal wind between easterlies and westerlies in the tropical stratosphere.

The 1935 Labor Day Storm rounded the west coast of the Florida Peninsula before impacting the Florida Panhandle, while the Long Island Express in 1938 traveled a due north trajectory before hitting western Connecticut and eastern New York.

“Looking at analogs and current patterns greatly impacts the upcoming hurricane season. The major disruptive and damaging hurricane threat area will be in the area that was damaged back in ’04 and ’05 across the Gulf,” Bastardi added. “It’s not the number of storms, but the intensity that will be the main concern. Since we are in the early stages of the AMO, the events of the late ’30s [are] the basis of the upcoming hurricane forecast, but until spring is over, nothing can be specifically pinpointed on direct impact.”

Bastardi said 2007 could display the intensity of 1935, but the number of storms could be equivalent to 1936. “Trying to determine what part of a three- to four-year cycle we are in is difficult to determine,” he added. “1995-96 were big landfall years followed by a drought in 1997, only to pick up again in 1998-99. Perhaps, last year could have been that similar drought year.”

The forecaster added that there is an increased threat in the Florida/Gulf Coast region. “With the exception of the western Gulf, which was jacked up because of the ’54/’99 analogs, the Gulf forecast was hugely bearish for hurricane activity,” Bastardi said. “The pure numbers I had were almost zero in the eastern Gulf and had to be adjusted up to get the forecast to where it was. It is not unlike the Gray Klotzbach adjustment up from the raw number to 17. In other words, the actual objective idea was on target and perhaps the shell-shock of the past couple of years contributed to what would have been a bold, perfect forecast (although you would have considered me mad as I simply said, ‘no Gulf action at all,’ and probably would have considered Bill and Phil underdone). But this year, I think major disruptive and damaging hurricanes are back into the areas that were damaged in ’04 and ’05. It is the intensity threat that scares me, not the number or overall storms at this time.”

In addition to Florida and the Gulf of Mexico, Bastardi described New England as “fair game from now on until 2025,” although he noted that the most frequent threats to the Northeast should be later in the run of the cycle. He said his statement last year that two major hurricanes would hit the Northeast within the next 10 years, sooner rather than later, still stands. “The summer temperature and hurricane pattern [last year] was so close to 1954 it can mean one of two things — we were unlucky in ’54 or lucky last year,” he said. “Ernesto came on the exact date of Carol, but the track some 100 miles west of Carol up the East Coast spared what should have been a devastating hurricane. As it was, damage to the coastal areas north of Cape Hatteras was greater than Floyd. Florence was 250 miles east of Edna’s path on the very same day as 1954. The number one target area last year, relative to averages, was the Canadian Maritimes.”

Bastardi said the East Coast is open, but he does not at this time have the same kind of support he had for last year of shifting tracks east. “Since I believe we are in the early to middle stages of the AMO, the backdrop of the late ’30s is the canvas on which the hurricane forecast is being painted, but it takes until spring is done for me to really hone in on where I think where impact is most likely.”

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 CSU 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.

©Copyright 2007Intelligence Press Inc. All rights reserved. The preceding news reportmay not be republished or redistributed, in whole or in part, in anyform, without prior written consent of Intelligence Press, Inc.