The 2006 Atlantic hurricane season was significantly less active than the record previous season. It marked the first since 2001 in which no hurricanes made landfall in the United States, and was the first since 1994 that no tropical cyclones formed during October. Following the intense activity of 2005, forecasters predicted that the 2006 season would be only slightly less active. Instead a rapidly forming moderate El Niño event in 2006, activity was slowed by the presence of the Saharan Air Layer over the tropical Atlantic and the steady presence of a robust secondary high pressure area to the Azores high centered around Bermuda. There were no tropical cyclones after October 2.
Tropical Storm Alberto was indirectly responsible for two deaths when it made landfall in Florida. Hurricane Ernesto caused heavy rainfall in Haiti, and directly killed at least seven in Haiti and the United States. Four hurricanes formed after Ernesto, including the strongest storms of the season, Hurricanes Helene and Gordon. In total, the season was responsible for 14 deaths and $500 million (2006 USD; $576 million 2018 USD) in damage. The calendar year 2006 also saw Tropical Storm Zeta, which arose in December 2005 and persisted until early January, only the second such event on record. The storm can be considered a part of the 2005 and 2006 seasons, although it occurred outside of the June 1 – November 30 windows during which most Atlantic basin tropical cyclones form.
Klotzbach's team (formerly led by Gray) has defined the average number of storms per season (1950–2000) as 9.6 tropical storms, 5.9 hurricanes, and 2.3 major hurricanes (storms exceeding Category 3 strength in the Saffir-Simpson Hurricane Scale). A normal season, as defined by NOAA, has 6–14 named storms, with 4–8 of those reaching hurricane strength, and 1–3 major hurricanes.
Predictions of tropical activity in the 2006 season
On December 5, 2005, Klotzbach's team issued its initial extended-range forecast for the 2006 season, predicting an above average of 17 named storms, nine of them hurricanes, and five classified as Category 3 intensity or higher.
As in the 2005 season, the team predicted it was highly probable that at least one major hurricane would directly impact the United States. The forecast suggested an 81% probability that at least one major hurricane would strike the U.S. mainland, a 64% chance of at least one major hurricane striking the East Coast of the United States (including the Florida peninsula), and a 47% chance of at least one major hurricane striking the Gulf Coast of the United States from the Florida Panhandle westward. The team also predicted that the potential for major hurricane activity in the Caribbean was above average. A few months later, on April 4, 2006, CSU issued another forecast confirming its December predictions.
On May 22, 2006, NOAA released its pre-season forecast for the 2006 season. The prediction was for 13–16 named storms, 8–10 of those becoming hurricanes, and 4–6 becoming major hurricanes.
On May 31, 2006, Klotzbach's team released its final pre-season forecast for 2006, confirming its earlier prediction.
On August 3, 2006, Klotzbach's team lowered its season estimate to 15 named storms, with 7 becoming hurricanes and 3 becoming major hurricanes, noting that conditions had become less favorable for storms than they had been earlier in the year. The sea-level pressure and trade wind strength in the tropical Atlantic were reported to be above normal, while sea surface temperature anomalies were on a decreasing trend.
On August 8, 2006, NOAA revised its season estimate to 12–15 named storms, with 7–9 becoming hurricanes and 3–4 becoming major hurricanes. The reduction was attributed to less favorable environmental conditions, a decrease in La Niña conditions, and the lack of a "very persistent upper-level ridge pattern over the eastern U.S. and western Atlantic."
On September 1, Klotzbach's team also revised its season estimate, to 13 named storms, 5 hurricanes and 2 major hurricanes, citing a larger volume of the Saharan Air Layer and an El Niño trend in the Pacific. The team again reduced the number of tropical storms expected for the season a month later, on October 3, with an updated forecast of 11 named storms, 6
hurricanes and 2 major hurricanes, citing the ongoing El Niño.
The season started on June 1, 2006, and officially ended on November 30, 2006. These dates conventionally delimit the period of each year when most tropical cylones form in the Atlantic basin. Ten days into the start of the season, Tropical Storm Alberto developed in the Caribbean Sea, and after four months of activity, Hurricane Isaac dissipated on October 3 south of Newfoundland. Compared to the devastating 2005 Atlantic hurricane season, 2006 was not severe in terms of deaths and damage.three tropical storms made landfall in the United States. The first of them, Tropical Storm Alberto, made landfall in Florida with winds of 50 mph (80 km/h), causing flooding and light damage.Tropical Storm Beryl made landfall on Nantucket, but left little impact. The third and more significant storm was Hurricane Ernesto, which killed two people in Virginia and two in Florida, as well as causing $500 million in damage (2006 USD). During the season, only one tropical cyclone in the Atlantic – Alberto – affected Mexico. Canada was affected by several tropical cyclones during 2006, including Alberto, the unnamed storm, Beryl, Florence, and Isaac.
The National Hurricane Center's pre-season activity outlook predicted 13–16 named storms, 8–10 hurricanes and 4–6 major hurricanes.
They also predicted a high risk of at least one major hurricane strike to the Southeast United States. In the event, only ten storms formed during the season, the lowest number since the 1997 season, when there were seven. Five of the ten storms developed into hurricanes—also the lowest number since 1997—and only two attained major hurricane status, tying with 2002 for the fewest since 1997. Only one named storm was observed during October, the lowest number since 1994, when none were seen during that month. Additionally, only three named storms made landfall in the United States, the fewest since 2001. Because of several factors, including a rapidly forming El Niño event, the Saharan Air Layer over the tropical Atlantic and the presence of a high pressure area to the Azores high situated near Bermuda, it contributed to a below average season. Also, sea surface temperatures in the western Atlantic were just at or slightly below average. In contrast, sea surface temperatures during the 2005 season were well above average.
Overall, the season's activity was reflected with a low cumulative accumulated cyclone energy (ACE) rating of 79. 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. Subtropical cyclones are excluded from the total.
On June 10, an area of disturbed weather associated with a broad low pressure area off the coast of Belize organized over the warm waters of the Caribbean Sea into the first tropical depression of the season. It dropped light rainfall in Mexico, with a 24-hour total peaking at 4 inches (100 mm) in Peto, Yucatán. Southwesterly vertical wind shear initially prevented significant development, but as it moved closer to Florida, the depression strengthened into a tropical storm on June 11. Passing over the warm, deep water of the Loop Current allowed accelerated development, and the cyclone reached its peak winds of 70 mph (115 km/h), just shy of hurricane strength. Subsequent weakening occurred as it moved over the cooler waters of the continental shelf, and Alberto made landfall near Adams Beach, Florida, on June 14 with winds of about 45 mph (72 km/h). Losing its tropical characteristics, Alberto moved northeastward and produced heavy rainfall in South Carolina and North Carolina. The remnants tracked off the East Coast and transitioned into a powerful extratropical storm which affected Nova Scotia with high winds, heavy rain, and rough surf, leaving four fisherman missing offshore.
Alberto caused record rainfall in North Carolina, peaking at eight in (200 mm). In Florida, two people died, and damage estimated at $250,000 (2006 USD; $288 thousand 2018 USD) was caused. Later, the storm left four sailors missing about 230 miles (370 km) south of Nova Scotia.
On July 17, a cold front moved off the Northeast United States coast and stalled; the tail end of the front spawned a low pressure system south of Nantucket, which tracked to the northeast along the front. Convection increased for a short time, before reaching colder waters and dissipating. Although the system was not believed to be tropical during its existence, post-season analysis revealed that it had attained tropical characteristics for 30 hours, and so it was designated an unnamed tropical storm. The storm became a remnant low on July 18 southeast of Nova Scotia before later dissipating northeast of Cape Race, Newfoundland. As the storm entered the area of responsibility of the Canadian Hurricane Centre, a buoy recorded sustained winds of 36 mph (56 km/h) with gusts up to 44 mph (70 km/h).
The same frontal system that developed the previous system spawned another low pressure area east of North Carolina. On July 18, it developed into a tropical depression, and with associated deep convection, the storm organized sufficiently to be upgraded to Tropical Storm Beryl on July 19. It tracked northeast and passed over Nantucket before dissipating southwest of Nova Scotia on July 21. Waves along the southern coast of Nantucket reached 10 feet (3.0 m) in height as the storm approached the island, resulting in four people being rescued by lifeguards from rip currents. The remnants of Tropical Storm Beryl dropped moderate precipitation in Atlantic Canada, with totals of up to 3.5 inches (88 mm); in some locations 1 inch (25 mm) of rain fell in an hour. Moderate winds were reported along its path, which peaked at 60 mph (96 km/h) in southern Nova Scotia.
By late July, a tropical wave moved off the coast of Africa and traversed the Atlantic Ocean. The associated convection organized and became a tropical depression on July 31 about 160 miles (260 km) east of Antigua. The depression tracked westward and soon intensified into Tropical Storm Chris before reaching peak winds of 65 mph (100 km/h) northeast of the United States Virgin Islands. The storm was forecast to strengthen further and become a hurricane as it moved into the Bahamas. However, Chris began to be affected by wind shear and became disorganized. The storm weakened to a tropical depression on August 4, and dissipated as it approached the Cuban coast on August 5.
The storm's effects were limited to moderate rainfall in Hispaniola and Cuba. Cruise lines such as Royal Caribbean re-routed their ships to avoid the storm. In Puerto Rico, rainfall from the storm caused the Fajardo River to overflow its banks. The overflown waters temporarily closed a highway in the northeastern portion of the island. Rainfall reached up to 2 inches (50 mm) across portions of Hispaniola, the Turks and Caicos, the Bahamas, and eastern Cuba, and reached 4 inches (100 mm) in some mountainous areas.
On August 20 a tropical wave emerged off the coast of Africa for the Atlantic Ocean. Immediately following, the wave developed convective banding and a broad circulation. At 1800 UTC on August 21, a tropical depression formed to the south-southeast of the Cape Verde Islands. The depression was a large, well-organized system, and tracking west-northwestward it intensified into Tropical Storm Debby on August 23.
Later on August 23, the storm attained peak winds of 50 mph (80 km/h), which it maintained for about two days. However, Debby entered a dry and stable air mass and deteriorated in organization. An upper-level trough increased southerly wind shear and displaced the convection from the center. The cyclone began to weaken, and on August 26 Debby weakened to a tropical depression before degenerating into a remnant low. The circulation lasted another two days.
Hurricane Ernesto originated from a tropical wave which moved off the coast of Africa on August 18. The wave progressed westward and reached the Western Atlantic, spawning a tropical depression on August 24 near the Windward Islands. It moved west-northwestward through the Caribbean Sea and intensified into Tropical Storm Ernesto on August 25. The storm briefly attained hurricane status on August 27 to the southwest of Haiti, before land interaction caused weakening. Ernesto made landfall near Guantanamo Bay, Cuba, early in the morning on August 28 as a tropical storm. At one point the storm was predicted to become a major hurricane in the Gulf of Mexico and threaten parts of the Gulf Coast. However, Ernesto moved much farther east than anticipated, and made landfall as a tropical storm on the southern tip of Florida on August 29. Ernesto retained tropical storm strength as it crossed Florida and emerged from land near Cape Canaveral, and was just below hurricane strength when it made landfall again in North Carolina on August 31. Ernesto transitioned into an extratropical cyclone over Virginia on September 1, which ultimately dissipated over Quebec on September 4.
Early in its duration, Ernesto killed five people in Haiti from rainfall. Later, two people died in Florida in traffic accidents due to slick roads. Damage was heaviest in Virginia, where heavy rains left severe flooding. Damage in the United States was estimated at $500 million (2006 USD).
Hurricane Florence originated on September 3 from the complex merging of two tropical waves, creating one large low pressure area. The disturbance moved westward and became a tropical depression in the open waters of the Atlantic. On September 5, it organized further and was upgraded into Tropical Storm Florence. With a disorganized structure and multiple circulation centers, Florence remained a weak tropical storm for several days, even after external conditions became favorable for strengthening. Florence tracked west-northwest and intensified into a hurricane on September 10 while south of Bermuda. The storm passed just to the east of Bermuda as a Category 1 hurricane on the Saffir-Simpson hurricane scale as it reached its peak intensity of 90 mph (145 km/h). It moved north before losing its tropical characteristics and passing over the Canadian Maritimes as a strong extratropical storm.
Large swells, rip tide, and undertow were reported on Bermuda, the Leeward Islands, the Virgin Islands, and Hispaniola. Florence affected Bermuda with wind gusts up to 115 mph (185 km/h) and heavy rain which left 23,000 houses without electricity. In all, the storm caused $200,000 (2006 USD; $231 thousand 2018 USD) in damage. Florence then brought heavy rains across Newfoundland as an extratropical storm, destroying one house and causing minor damage to several others. There were no fatalities as a result of the hurricane.
A tropical wave moved off the coast of Africa on September 1. The wave tracked westward across the Atlantic for several days until it reached an area of relaxed wind shear and its associated low pressure area organized into a tropical depression. It moved east-northeast and was upgraded to Tropical Storm Gordon on September 11, while located over the open waters of the Atlantic. Gordon turned north, and became a hurricane on September 13. It intensified to Category 3 status on the Saffir-Simpson hurricane scale and reached its peak intensity of 120 mph (195 km/h) on September 14. Tracking northward, it began to lose tropical characteristics. On September 20, the system affected Britain with high winds and heavy rain as an extratropical cyclone. During Gordon's passage through Britain, 120,000 homes were left without power after winds of 80 mph (130 km/h) affected the country.
On September 11, a vigorous tropical wave moved off the west coast of Africa. The wave organized rapidly and spawned a tropical depression to the south-southeast of Cape Verde. On September 14, the depression intensified into Tropical Storm Helene while tracking west-northwest. Helene continued to intensify and was upgraded to a hurricane on September 16. The storm began to execute a northward track, and reached Category 3 hurricane status on the Saffir-Simpson hurricane scale on September 18, before reaching its peak intensity of 120 mph (195 km/h). It started to weaken when it reached the cold waters of the North Atlantic, and Helene dissipated on September 20, without having had major effects on land other than moderate wind gusts in the British Isles.
Hurricane Isaac originated in a tropical wave that moved off the coast of Africa on September 18. The wave tracked west, produced a tropical depression, and became a tropical storm on September 28. Isaac moved north-northwest and was upgraded to a hurricane on September 30. It turned north and reached its peak intensity of 85 mph (135 km/h) before weakening and brushing Nova Scotia. Isaac produced moderate winds on land in Newfoundland, peaking at 60 mph (96 km/h) with a sustained wind of 46 mph (74 km/h) was recorded.
The names listed were used for named storms formed in the North Atlantic during 2006. The list is the same as that used in the 2000 season except for Kirk, which replaced Keith. No storm was given a previously unused name, for the first time since the 1993 season. It was the first hurricane season since the 1997 season that no Atlantic names were retired. The same list is currently being used in the 2012 season.