The 2008 Atlantic hurricane season was the most destructive Atlantic hurricane season since 2005, causing over 1,000 deaths and nearly $50 billion (2008 USD) in damage. It was an above-average season, featuring sixteen named storms, eight of which became hurricanes, and five which further became major hurricanes. It officially started on June 1 and ended on November 30. These dates conventionally delimit the period of each year when most tropical cyclones form in the Atlantic basin. However, the formation of Tropical Storm Arthur caused the season to start one day early. It was the only year on record in which a major hurricane existed in every month from July through November in the North Atlantic. Bertha became the longest-lived July tropical cyclone on record for the basin, the first of several long-lived systems during 2008.
The season was devastating for Haiti, where nearly 800 people were killed by four consecutive tropical cyclones (Fay, Gustav, Hanna, and Ike), especially Hurricane Hanna, in August and September. These four storms caused about $1 billion in damage in Haiti alone. The precursor to Kyle and the outer rain bands of Paloma also impacted Haiti. Cuba also received extensive impacts from Gustav, Ike, and Paloma, with Gustav and Ike making landfall in the country at major hurricane intensity and Paloma being a Category 2 when striking the nation. More than $10 billion in damage and 8 deaths occurred there.
Ike was the most destructive storm of the season, as well as the strongest in terms of minimum barometric pressure, devastating Cuba as a major hurricane and later making landfall near Galveston, Texas, as a large high-end Category 2 hurricane. One very unusual feat was a streak of tropical cyclones affecting land, with all but one system impacting land in 2008. The unusual number of storms with impact led to one of the deadliest and destructive seasons in the history of the Atlantic basin, especially with Ike, as its overall damages made it the second-costliest Atlantic hurricane on record at the time, although it has since been surpassed by several hurricanes.
Seasonal forecasts
Dr. Philip J. Klotzbach, Dr. William M. Gray, and their associates at Colorado State University (CSU) – as well as forecasters at National Oceanic and Atmospheric Administration (NOAA), Met Office (UKMO), Tropical Storm Risk (TSR), Weather Services International (WSI) – issued forecasts of hurricane activity prior to the start of the season.
Klotzbach's team (formerly led by Gray) defines the average number of storms per season (1950 to 2000) as 9.6 tropical storms, 5.9 hurricanes, and 2.3 major hurricanes (storms reaching at least Category 3 strength in the Saffir-Simpson Hurricane Scale). A normal season, as defined by NOAA, has 9 to 12 named storms, with 5 to 7 of those reaching hurricane strength, and 1 to 3 major hurricanes.
Pre-season forecasts
The first forecast for the 2008 hurricane season was released by CSU on December 7, 2007. In its report, the organization predicted 13 named storms, 7 hurricanes, 3 major hurricanes, and an annual Accumulated Cyclone Energy (ACE) index of 115 units. The odds of a major hurricane landfall in the Caribbean and along the United States were projected to be above average. 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. It is only calculated for full advisories on tropical systems at or exceeding 39 mph (63 km/h), which is the threshold for tropical storm strength. The odds of a major hurricane landfall in the Caribbean and along the United States were projected to be above average in the CSU forecast.
Three days later, TSR—a public consortium consisting of experts on insurance, risk management, and seasonal climate forecasting at University College London—called for a very active season featuring 15.4 (±4.7) named storms, 8.3 (±3.0) hurricanes, 3.7 (±1.8) major hurricanes, and a cumulative ACE index of 149 (±66) units. Mirroring CSU, the group assigned high probabilities that the United States and Lesser Antilles landfalling ACE index would be above average. On January 3, 2008, WSI projected 14 named storms, 7 hurricanes, and 3 major hurricanes.
In April, CSU slightly raised their values owing to a favorable Atlantic sea surface temperature configuration during the preceding month, upping the projected numbers to 15 named storms, 8 hurricanes, and 4 major hurricanes. TSR, in contrast, slightly reduced their numbers on April 7 due to cooler projections for Atlantic Ocean temperatures compared to their December forecast. WSI on April 23 raised the expected number of hurricanes from 7 to 8 and major hurricanes from 3 to 4 while leaving the number of named storms unchanged. On May 22, the NOAA's Climate Prediction Center announced their first seasonal outlook for the 2008 season, highlighting 65 percent odds of an above-normal season, 25 percent odds for a near-normal season, and 10 percent odds of a below-average season. A range of 12 to 16 named storms, 6 to 9 hurricanes, and 2 to 5 major hurricanes was provided, each with 60 to 70 percent probability. The CPC, alongside TSR and CSU, highlighted the ongoing multi-decadal period of enhanced Atlantic tropical cyclone activity, the ongoing La Niña in the Pacific, and warmer than average ocean temperatures across the eastern tropical Atlantic as the basis for their predictions.
Midseason outlooks
On June 3, CSU released an updated outlook for the season but left their values from April unchanged. Examining conditions in April and May, the organization compiled a list of hurricane seasons with similar conditions: 1951, 1961, 2000, and 2001. TSR slightly lowered their numbers in their June 5 update but continued to predict an above-average season. Meanwhile, on June 18, the UKMO released their seasonal forecast, assessing a 70 percent probability the number of tropical storms would fall between 10 and 20, with 15 tropical storms noted as the most likely value in 2008. No projections for the number of hurricanes, major hurricanes, or ACE were given. On July 2, WSI held firm to their April forecast; the organization was forced to slightly increase the number of named storms and hurricanes later that month. On July 4, TSR slightly raised their forecast. Following an active start to the season, CSU upped their predictions in an August 5 update, calling for 17 named storms, 9 hurricanes, 5 major hurricanes, and an ACE index of 175 units. TSR released their final outlook for the season that day, raising their values to 18.2 (±2.9) named storms, 9.7 (±1.7) hurricanes, 4.5 (±1.4) major hurricanes, and an ACE index of 191 (±42) units. On August 7, NOAA's CPC raised their probability of an above-average season from 65 percent to 85 percent. The final outlook yielded a 67 percent chance of 14 to 18 named storms, 7 to 10 hurricanes, and 3 to 6 major hurricanes. WSI, meanwhile, issued their final seasonal outlook on August 27, reaffirming their numbers from the previous month.
Seasonal summary
The 2008 hurricane season officially began on June 1, though Tropical Storm Arthur formed one day earlier. The season was above-average, featuring 16 named storms, 8 of which intensified into hurricanes, while 5 of the hurricanes reached major hurricane status. Despite a La Niña dissipating early in the summer months, atmospheric conditions remained favorable for tropical cyclogenesis, including abnormally low wind shear between 10°N and 20°N. Additionally, sea surface temperatures in the deep tropics and the Caribbean Sea were fifth warmest since 1950. The season saw the first occurrence of major hurricanes in the months of July through November. Four storms formed before the start of August, and the season also had the earliest known date for three storms to be active on the same day: Hurricane Bertha, and Tropical Storms Cristobal and Dolly were all active on July 20. This season was also one of only ten Atlantic hurricanes seasons on record to have a major hurricane form before August, as well as one of only seven Atlantic seasons to feature a major hurricane in November. The final tropical cyclone, Hurricane Paloma, degenerated into a remnant low-pressure area over Cuba on November 9, three weeks before the season officially ended on November 30.
The season was devastating for Haiti, where four consecutive tropical cyclones – Fay, Gustav, Hanna, and Ike – killed at least 793 people and caused roughly $1 billion in damage. Hurricane Ike was the most destructive storm of the season, as well as the strongest, devastating Cuba as a major hurricane and later making landfall near Galveston, Texas, at Category 2 (nearly Category 3) intensity. The cyclone caused a particularly devastating storm surge along the western Gulf Coast of the United States due to in part to its large size. Ike was the second-costliest hurricane in the Atlantic at the time, but has since dropped to sixth following Sandy, Harvey, Irma, and Maria. Hanna was the deadliest storm of the season, killing 533 people, mostly in Haiti. Gustav was another very destructive storm, causing up to $8.31 billion in damage to Haiti, Jamaica, the Cayman Islands, Cuba, and the United States. Dolly caused up to $1.6 billion in damage to south Texas and northeastern Mexico. Bertha was an early season Cape Verde-type hurricane that became the longest-lived July North Atlantic tropical cyclone on record, though it caused few deaths and only minor damage. The Atlantic basin tropical cyclones of 2008 collectively caused roughly $49.4 billion in damage and at least 1,074 fatalities. At the time, the season ranked as the third costliest on record, behind only 2004 and 2005. However, it has since fallen to eighth.
Other notable storms included Tropical Storm Fay, which became the first Atlantic tropical cyclone to make landfall in the same U.S. state on 4 occasions; Tropical Storm Marco, the smallest Atlantic tropical cyclone on record; Hurricane Omar, a powerful late-season major hurricane which caused moderate damage to the ABC islands, Puerto Rico, and the Virgin Islands in mid-October; and Hurricane Paloma, which became the third-strongest November hurricane in recorded history and caused about $454.4 million in damage to the Cayman Islands and Cuba. The only storm of the season to not reach tropical storm status, Tropical Depression Sixteen, contributed to a significant flooding event in Central America, with the cyclone itself directly blamed for at least nine deaths.
Overall, the season's activity was reflected with a total cumulative ACE rating of 145.7. This was well above the normal average, and nearly double the rating given to each of the two preceding seasons (79 – 2006; 74 – 2007).
Systems
Tropical Storm Arthur
In late May, a westward-moving tropical wave and the mid-level remnants of Tropical Storm Alma from the East Pacific combined over the northwestern Caribbean Sea. This led to the formation of Tropical Storm Arthur by 00:00 UTC on May 31. The cyclone reached its peak intensity with winds of 45 mph (72 km/h) six hours after development, and it made landfall at 09:00 UTC on June 1 about halfway between Belize City, Belize, and Chetumal, Yucatán Peninsula, at that strength. Once inland, Arthur quickly lost organization and degenerated to a remnant area of low pressure around 00:00 UTC on June 2. It dissipated six hours later. In conjunction with Alma, Tropical Storm Arthur dropped over 12 in (300 mm) of rainfall across portions of Belize, destroying roads, washing out bridges, and damaging 714 homes. Total damage was estimated at $78 million, and five deaths were recorded.
Hurricane Bertha
A well-defined tropical wave left Africa on July 1 and organized into a tropical depression by 06:00 UTC on July 3. Six hours later, it intensified into Tropical Storm Bertha, the easternmost tropical storm on record in the Atlantic during July. Steered on a west-northwest or northwest course, Bertha reached hurricane strength around 06:00 UTC on July 7. The cyclone then underwent a period of rapid intensification that brought it to its peak as a Category 3 hurricane with winds of 125 mph (201 km/h) later that day. Structural changes and a more hostile environment caused the storm to fluctuate in intensity as it passed east of Bermuda. By July 19, however, the storm began to undergo extratropical transition, a process it completed by 12:00 UTC the next morning. The post-tropical storm continued northeast and merged with a larger extratropical low near Iceland on July 21. Lasting a duration of 17 days, Bertha became the longest-lived Atlantic tropical cyclone on record during the month of July.
As the cyclone passed east of Bermuda, it produced strong wind gusts peaking at 91 mph (146 km/h). Power lines were downed, cutting electricity to about 7,500 homes, and tree branches were snapped. Heavy rainfall, reaching 4.77 in (121 mm) at L.F. Wade International Airport, flooded roadways. Meanwhile, Bertha produced large waves and rip currents along the U.S. East Coast, resulting in 3 deaths offshore New Jersey and 57 water rescues in Atlantic City alone. Fifty-five people were injured off the coast of Delaware while an additional four individuals were injured off North Carolina. At Wrightsville Beach in particular, officials estimated at least 60 water rescues over a 48-hour span. Over a seven-day period beginning on July 9, the storm contributed to 1,500 ocean rescues in Ocean City, Maryland.