It Only Takes One
Long-range forcasts are difficult, but CSU's team sees seven hurricanes ahead in 2008.

2007 TURNS OUT AVERAGE
Given that a variety of atmosphere/ocean conditions interact with each other to cause year-to-year and month-to-month hurricane variability, and that the interactions between them are complicated, the difficulty in making short-range forecasts is understandable. What began as an above-average forecast for hurricane activity in 2007 by the CSU forecasting team (see HP, Spring 2007, page 22), turned out to be much closer to average. “Our 2007 seasonal hurricane forecast was not particularly successful,” writes Philip J. Klotzbach, who co-authored a summary of the 2007 season with William Gray. “We anticipated an above-average season, and the season had activity at approximately average levels.

“Our August-only forecast was quite successful,” he continues. “Our September and October-November forecasts were not successful. We predicted September and October-November to be active. September experienced activity at average levels, while below-average activity occurred in October-November.”
The CSU team updates its forecast throughout the season as data is collected. As it turns out, its pre-season forecast issued December 8, 2006, was closer to being correct than its mid-season update issue August 3, 2007.

2007 SEASON HIGHLIGHTS
A number of characteristics of the 2007 hurricane season stand out. Among them:

• Another early-starting season. Andrea formed on May 9. The climatological average date for the first named storm in the Atlantic, based on 1944-2005 data, is July 10.

• 14 named storms formed. Since 1995, 12 out of 13 seasons have had more than the 1950-2000 average of 10 named storms.

• Six hurricanes formed. This is very close to the long-term average (5.9 hurricanes per year).

• 5.75 intense hurricane days. Despite low values of named storm days and hurricane days, intense hurricane days were at above-average levels.

• Hurricane Dean became a Category 5 hurricane in August. Hurricane Katrina became a Category 5 hurricane in August 2005. The most recent year with a Category 5 hurricane in August prior to 2005 was Hurricane Andrew in 1992.

• Hurricane Humberto became the first hurricane to make landfall in Texas since Hurricane Claudette in 2003.

One tropical depression, two tropical storms and one hurricane made U.S. landfall in 2007. Tropical Depression Barry, Tropical Storms Erin and Gabrielle and Hurricane Humberto. Humberto incurred approximately $500 million in total damage in Texas. Damage from Erin is unavailable. This is the second year in a row that the United States has experienced fairly little damage from tropical cyclones.

2007 SEASON SYNOPSIS

Intense Hurricane Dean: Dean formed on August 13. A combination of vertical wind shear and warm sea surface temperatures aided Dean’s intensification into a hurricane on August 16. By August 18, Dean had become a Category 4 storm. On August 21, Dean was upgraded to a Category 5 hurricane with maximum sustained winds of 145 knots. Dean made landfall on the east coast of Mexico’s Yucatan Peninsula as a Category 5 hurricane later on August 21. It dissipated over the high terrain of Mexico early on August 23. Forty-two deaths have been attributed to Hurricane Dean, while total damage is estimated at nearly $4 billion dollars.

Intense Hurricane Felix: Felix formed on August 31 about 200 miles east of the Windward Islands. Felix was imbedded in a weak shear and warm sea surface temperature environment, and it intensified into a hurricane in just 15 hours. It continued to intensify rapidly over the warm waters of the eastern Caribbean, becoming the second major hurricane of the season on September 2. By late on September 2, Felix intensified into the second Category 5 hurricane of the year. It made landfall on September 4 near the Nicaragua/Honduras border as a Category 5 storm. The system dissipated rapidly over land, becoming a tropical storm early on September 5 and a remnant low later that day. At least 133 deaths have been reported due to Felix, while damage estimates remain unknown.

Hurricane Humberto: Humberto formed in the western Gulf of Mexico on September 12. Humberto intensified into a tropical storm later on September 12. Humberto began to rapidly intensify, becoming a hurricane early on September 13. Humberto crossed the Texas coast near High Island later on September 13. The system rapidly weakened to a tropical depression after making landfall. Humberto was notable for its rapid intensification from a 30-knot tropical depression to a 75-knot hurricane. This intensification was accomplished over an 18-hour period, making it the fastest development in recorded history for the Atlantic basin. One fatality has been attributed to Humberto, while damage estimates are estimated to be near $50 million dollars.

Hurricane Karen: Karen developed on September 25. On September 26, Karen began to intensify and briefly reached hurricane intensity late in the day. Karen weakened to a minimal tropical storm on September 28 and further weakened to a tropical depression on September 29.

Hurricane Lorenzo: Lorenzo formed on September 25. Lorenzo slowly drifted westward. It rapidly intensified into a 50-knot tropical cyclone on September 27. It intensified further into a hurricane early on September 28. The system made landfall approximately 40 miles south of Tuxpan, Mexico, on September 28 as a 70-knot hurricane. It dissipated over the high terrain of Mexico later that day. Five fatalities have been attributed to Lorenzo. Damage estimates are not available.

Hurricane Noel: Noel formed on October 27. Noel was upgraded to a tropical storm and intensified into a 50-knot tropical cyclone late on October 28. The system intensified further on November 1, becoming a hurricane late in the day. A mid-latitude short-wave trough interacted with Noel, causing the system to accelerate northeastward. It maintained hurricane intensity until November 2. Noel brought heavy rains and strong winds to eastern New England and the Atlantic Provinces of Canada.

ATLANTIC BASIN HURRICANE FORECAST FOR 2007

Dec 8, '06 Preseason:
Named Storms - 14
Hurricanes - 7
Intense Hurricanes - 3

Aug 3, '07 Preseason:
Named Storms - 15
Hurricanes - 8
Intense Hurricanes - 4

Observed 2007 Total:
Named Storms - 14
Hurricanes - 6
Intense Hurricanes - 2

ATLANTIC BASIN HURRICANE FORECAST FOR 2008

1950 - 2000 Average:
Named Storms - 9.6
Hurricanes - 5.9
Intense Hurricanes - 2.3

Dec. 7 Forecast:
Named Storms - 13
Hurricanes - 7
Intense Hurricanes - 3

LANDFALL PROBABILITIES FOR 2008 (in percent):

Average Last 100 years:
Entire U.S. Coastline - 52
U.S. East Coast - 31
Gulf Coast - 30

2008 Season Forecast:
Entire U.S. Coastline - 60
U.S. East Coast - 37
Gulf Coast - 36