The 2007 Atlantic hurricane season was the first season since 2003 to feature tropical activity both before and after the official bounds of the season. Although there were an above-average number of named storms during the season – 15, most of them were weak and short-lived. Despite the predominance of weak systems, this was the first season on record to feature more than one Category 5 landfalling hurricane. It produced 17 tropical cyclones, 15 tropical storms, six hurricanes, and two major hurricanes. It officially started on June 1 and ended on November 30, dates which conventionally delimit the period during which most tropical cyclones form in the Atlantic Ocean, although as shown by Subtropical Storm Andrea and Tropical Storm Olga in early May and early December, respectively, the formation of tropical cyclones is possible at any time of the year. The first system, Subtropical Storm Andrea, developed on May 9, while the last storm, Tropical Storm Olga, dissipated on December 13. The most intense hurricane, Dean, was, at the time, the third most intense landfalling Atlantic storm on record. It was the second on record in which an Atlantic hurricane, Felix, and an eastern Pacific hurricane, Henriette, made landfall on the same day. September had a then record-tying eight storms, until it was surpassed in 2020. However, the strengths and durations of most of the storms were low.
Pre-season forecasts by Colorado State University called for 14 named storms and 7 hurricanes, of which three were expected to attain major hurricane status. The National Oceanic and Atmospheric Administration (NOAA) later issued its initial forecast, which predicted 13 to 17 named storms, 7 to 10 hurricanes and three to five major hurricanes. After several revisions in the projected number of storms, NOAA and CSU lowered their forecasts by the middle of the season.
Several storms made landfall or directly affected land. Hurricanes Dean and Felix made landfall at Category 5 intensity, causing severe damage in parts of Mexico and Central America, respectively. Both storm names, as well as Noel, the name of a hurricane that affected the Caribbean, were retired from the naming list of Atlantic hurricanes. The United States was affected by five cyclones, although the storms were generally weak; three tropical depressions and only two tropical storms, Barry and Gabrielle, and one hurricane, Humberto, made landfall in the country. Elsewhere, three storms directly affected Canada, although none severely. The combined storms killed at least 416 people and caused about $3.24 billion (2007 USD, 5.04 billion 2026 USD) in damage.
Seasonal forecasts
Philip J. Klotzbach, William M. Gray, and their associates at Colorado State University issue forecasts of hurricane activity each year, separately from NOAA. Klotzbach's team, formerly led by Gray, determined the average number of storms per season between 1950 and 2000 to be 9.6 tropical storms, 5.9 hurricanes, and 2.3 major hurricanes (storms exceeding Category 3 on the Saffir–Simpson scale). A normal season, as defined by NOAA, has 9 to 12 named storms, of which five to seven reach hurricane strength, and one to three become major hurricanes.
Pre-season forecasts
On December 8, 2006, Klotzbach's team issued its first extended-range forecast for the 2007 season, predicting above-average activity (14 named storms, seven hurricanes, three of Category 3 or higher). It listed a 64 percent chance of at least one major hurricane striking the U.S. mainland. This included a 40 percent chance of at least one major hurricane strike on the East Coast, including the Florida peninsula, and a 40 percent chance of at least one such strike on the Gulf Coast from the Florida Panhandle westward. The potential for major hurricane activity in the Caribbean was forecast to be above average, and the team predicted that El Niño, associated with reduced hurricane activity in the Atlantic, would dissipate by the active portion of the season.
On April 3 a new forecast was issued, calling for a very active hurricane season of 17 named storms, nine hurricanes and five intense hurricanes. The increase in the forecast was attributed to the rapid dissipation of El Niño conditions. The team also forecast a neutral or weak-to-moderate La Niña and noted that sea surface temperatures were much higher than average. The estimated potential for at least one major hurricane to affect the U.S. was increased to 74 percent; the East Coast potential increased to 50 percent, and from the Florida Panhandle westward to Brownsville, Texas, the probability rose to 49 percent. However, the team's report noted that while they predicted an active season, it was not suggesting that 2007 would be "as active as the 2004 and 2005 seasons".
Midseason outlooks
On June 19 the UK Met Office (UKMO) issued a forecast of 10 tropical storms in the July to November period with a 70 percent chance that the number would be in the range of 7 to 13. On August 3, 2007, Klotzbach's team lowered its season estimate to 15 named storms, of which eight were to become hurricanes and four to become major hurricanes. Team members noted that conditions had become slightly less favorable for storms than earlier in the year. Sea surface temperature anomalies were cooler, and several Saharan Air Layer events had suppressed development of tropical cyclones. El Niño-Southern Oscillation (ENSO) conditions were also noted to have been slightly cooler.
On August 9, 2007, NOAA revised its season estimate slightly downwards to 13 to 16 named storms, of which seven to nine were to be hurricanes, and three to five major hurricanes. However, the agency reaffirmed its prediction of an above-average season, citing warmer-than-normal sea surface temperatures in parts of the Atlantic Ocean and Caribbean and the likelihood of La Niña conditions during the peak of the season.
Seasonal summary
Only two major hurricanes, storms of Category 3 intensity or higher, formed during the season, the fewest since the 1997 season. Named storms were active for 33.50 days during the season, the lowest number of active days since the 1994 season. There were only 11.25 days with active hurricanes, the lowest value since the 2002 season. Despite this, the number of days with major hurricanes was above the long-term average. Both major hurricanes, Dean and Felix, attained Category 5 status, and both made landfall at Category 5 intensity, making the 2007 season the first to feature two hurricanes doing each, both of which would not be repeated until 2017. When Hurricane Felix was upgraded to a Category 5 storm on September 2, it became the eighth to form in this basin since 2000. This gave the decade more hurricanes of such strength than any other on record. Hurricane Humberto was the first hurricane to make landfall in Texas since Hurricane Claudette in 2003.
Overall, the season's activity was reflected with a cumulative accumulated cyclone energy (ACE) rating of 73.9, which is below the long-term average of 93, and the lowest since 2002. ACE is, broadly speaking, a measure of the power of the hurricane multiplied by the length of time it existed, so storms that last a long time, as well as particularly strong hurricanes, have high ACEs. ACE is only calculated for full advisories on tropical systems at or exceeding 34 knots (39 mph; 63 km/h) or tropical storm strength. Although officially, subtropical cyclones, such as Andrea or the initial portions of Gabrielle, Jerry, and Olga, are excluded from the total, the figure above includes periods when storms were in a subtropical phase.
Systems
Subtropical Storm Andrea
A large extratropical cyclone formed offshore the mid-Atlantic on May 6. It deepened steadily along a cold front that pushed through Florida. After losing most of its baroclinic support, development ceased until its low moved into warmer waters near the Bahamas. However, interaction between the low and a strong high-pressure system to the north generated hurricane-force winds in the system. Decreasing wind shear allowed deeper convection to develop much closer to the center. By May 9, the system had transitioned into Subtropical Storm Andrea about 140 mi (225 km) southeast of Savannah, Georgia, immediately peaking with winds of 60 mph (95 km/h) and a minimum pressure of 1,001 mbar (29.6 inHg). Andrea then moved southward into an environment with higher wind shear, weakening to a subtropical depression on May 10. The storm degenerated into a remnant low on the next day about 70 mi (115 km) east of Ponce Inlet, Florida, as all significant convection had disappeared. Following intermittent bursts of convection, an advancing cold front pushed Andrea's remnants northward and eventually absorbed the system.
Andrea was the first pre-season storm to develop since Tropical Storm Ana in April 2003 and the first Atlantic named storm in May since Tropical Storm Arlene in 1981. Because Andrea never made landfall, most of the resulting damage was associated with large waves, higher than normal tides, associated coastal flooding, and beach erosion. In North Carolina, erosion left about 70 dwellings in imminent danger, while waves covered Highway 12 with sand and washed part of it away. From North Carolina to Florida, several vessels suffered damage and a few other went capsized or were lost. Winds generated by the storm contributed to the spread of wildfires in Florida and Georgia. Six deaths occurred in the United States, all due to waves generated by Andrea's precursor. The extratropical system which developed into Andrea also produced significant swells in the Bahamas.
Tropical Storm Barry
On May 30, a broad low-pressure area spawned from a westward-moving tropical wave offshore the east of the Yucatán Peninsula. The low organized into a tropical depression just north of the Yucatán Channel on June 1, the first day of the hurricane season. Six hours later, the depression intensified into Tropical Storm Barry. The storm moved north-northeastward and reached its peak intensity early on June 2 with winds of 60 mph (95 km/h) and a minimum pressure of 997 mbar (29.4 inHg). However, strong wind shear weakened Barry to a tropical depression before it made landfall on Anna Maria Island, Florida, several hours later. Barry became extratropical late on June 2 over eastern Georgia, but its remnants continued up the East Coast of the United States before being absorbed by a larger extratropical cyclone over eastern Quebec on June 5.
The precursor to Barry dropped heavy rains in parts of Cuba, with Sancti Spíritus Province recording up to 12 in (300 mm). More than 2,000 people fled their homes after streets flooded and waterways swelled. In Florida, the rainfall resulted in slick roads, which caused two traffic-related deaths, and a woman was killed after being injured by rough surf. Barry spawned a few tornadoes in the state, damaging a few homes and powe lines and knocking down some trees and fences. Up to 8 in (200 mm) of rain fell in Georgia at Mount Vernon, which was mostly beneficial due to assisting firefights with their response to the Bugaboo Fire. The remnants of Barry also caused some instances of flooding farther north and more than 60 traffic accidents in Virginia, resulting in 10 injuries. Damage from Barry and its remnants totaled around $118,000.
Tropical Storm Chantal
A frontal system moved off the Carolinas on July 21 and degenerated into a surface trough. After remaining nearly stationary northeast of the Bahamas, the system began organizing on July 28 as the motion became more northerly. On July 30, the low passed to the west of Bermuda as the thunderstorms became more organized. On July 31, Tropical Depression Three developed about 270 miles (430 km) north-northwest of Bermuda. Convection increased further over the center, and at around 06:00 UTC on July 31 the depression intensified into Tropical Storm Chantal. The storm continued northeastward, under the influence of a mid-level trough, and quickly reached peak winds of 50 mph (80 km/h). The storm tracked through an area of progressively cold waters and cooler air, causing Chantal to weaken. On August 1, the storm transitioned into an extratropical storm within the approaching cold front. Midday on August 1, the cyclone struck Newfoundland along the Avalon Peninsula, hitting the Placentia Area with full force. It subsequently intensified to attain winds of near hurricane-force. On August 3 the cyclone underwent a final weakening trend in the far northern Atlantic Ocean, and on August 5 the extratropical remnants of Chantal merged with another extratropical cyclone to the east of Iceland.
On Bermuda, the L.F. Wade International Airport recorded 2.12 in (54 mm) of precipitation, which represented about 35% of rainfall observed there in July 2007. The remnants of Chantal moved over the Avalon Peninsula of Newfoundland, producing wind gusts of 55 mph (88 km/h) at Cape Pine. Rainfall reached 7.89 in (200 mm) of rain fell in Argentia. Some homes suffered water damage and 10 communities became isolated after bridges and roads were washed out. Insured damage across the area totaled $25 million (2007 CAD, $24.3 million 2007 USD). The flooding led to a state of emergency. In Ship Harbour citizens were isolated for 5 days until a temporary road was made. Also in Spaniard's Bay, the flooding caused a bridge to depress about 1.5 feet (46 cm); The storm caused the annual Royal St. John's Regatta to be postponed.
Hurricane Dean
On August 11, a tropical wave moved off the west coast of Africa, and, encountering favorable conditions, quickly spawned Tropical Depression Four, roughly 520 mi (835 km) west-southwest of Cabo Verde. The depression moved briskly westward, south of a deep layered ridge, and was upgraded to Tropical Storm Dean on August 14. The storm continued to strengthen overnight as it gained organization, and became the first hurricane of the season on August 16. Dean passed into the Caribbean on the following day between the islands of Martinique and Saint Lucia as a Category 2 hurricane. In the warm waters of the Caribbean, Dean rapidly strengthened into a Category 5 hurricane with 165 mph (265 km/h) sustained winds. An eyewall replacement cycle weakened Dean, which then passed just south of Jamaica as a Category 4 hurricane on August 19.