| Category 3 hurricane (SSHS) | |
|---|---|
| Hurricane Bertha near its peak as a strong Category 3 hurricane on July 7, 2008 | |
| Formed | July 3, 2008 |
| Dissipated | July 21, 2008 (Extratropical after July 20) |
| Highest winds | 1-minute sustained: 125 mph (205 km/h) |
| Lowest pressure | 952 mbar (hPa; 28.11 inHg) |
| Fatalities | 3 direct |
| Damage | Minimal |
| Areas affected | Bermuda, Delaware, North Carolina, New Jersey, and Iceland |
| Part of the 2008 Atlantic hurricane season | |
Hurricane Bertha was both the longest-lived July Atlantic tropical cyclone on record,[1] and the easternmost form July tropical storm on record.[2] The second named storm, first hurricane, and first major hurricane of the annual hurricane season, Bertha originated from a tropical wave that emerged off the western coast of Africa on July 1, 2008. Tracking slowly towards the west-northwest, it developed into a tropical depression on July 3 and strengthened into a tropical storm shortly thereafter. Embedded within an environment conducive for intensification, Bertha attained hurricane status on the morning hours of July 7, and by the evening hours, a round of rapid intensification took place, at which time Bertha reached its peak intensity as a strong Category 3 hurricane on the Saffir–Simpson Hurricane Wind Scale. Executing a turn more towards the north-northwest, the hurricane began to feel the effects of higher wind shear and slightly cooler ocean temperatures, subsequently leading to weakening. On July 8, Bertha weakened to a minimal hurricane, but briefly attained Category 2 hurricane status after an eyewall replacement cycle. On July 13, Bertha weakened to a tropical storm and made its closest approach to Bermuda the following day. The storm briefly attained hurricane status on July 18 before transitioning into an extratropical cyclone two days later.
As a weak tropical cyclone, Bertha impacted the Cape Verde Islands with minimal rainfall and gusty winds; however, no deaths were reported and damage was minimal. Prior to Bertha's closest pass to Bermuda, flights were cancelled from the island to major United States cities. As the hurricane passed by, minimal rainfall was observed on the island, as well as tropical storm-force winds. Additionally, a hurricane watch was issued on July 15 in fear that Bertha would re-intensify before making its closest pass by the island. Along the United States East Coast, large swells and rough seas were recorded. Overall, 3 fatalities are directly attributed to the hurricane, but damage was minimal.
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Hurricane Bertha was first identified as a broad area of low pressure accompanying a tropical wave over western Africa in late June 2010. Tracking generally west-northwestward, the system emerged into the eastern Atlantic Ocean on July 1. Steady development took place as convection – thunderstorm activity – consolidated around its center, and spiral banding became better established. At 0300 UTC on July 3, the wave and associated low-pressure area was deemed sufficiently organized to be designated as Tropical Depression Two while centered roughly 220 mi (350 km) south-southeast of the Cape Verde Islands.[3] At this time, the National Hurricane Center (NHC) noted that the depression displayed intense convection near the center and increasingly pronounced banding features in the northwestern portion of the circulation. Additionally, the organization mentioned that the global models performed well in predicting the tropical cyclogenesis of Bertha, with the Global Forecast System (GFS) forecasting development of Bertha a week out.[4] Six hours later, the depression attained gale-force winds, and was subsequently upgraded to Tropical Storm Bertha after satellite estimates from both the Satellite Analysis Branch (SAB) and Tropical Analysis and Forecast Brach (TAFB) supported an intensity of 40 mph (55 km/h).[3][5]
Moving west-northwestward around the southern periphery of a mid-level ridge situated over the central Atlantic,[6] Bertha briefly stopped intensifying as cloud tops associated with the system warmed; despite this, banding features remained well-defined. However, the intensification process began shortly thereafter as a burst of deep convection developed atop the cyclone's center. The system was located within an environment conducive for strengthening, although Lixion Avila noted in his 5:00 p.m. AST (2100 UTC) forecast discussion that Bertha would be entering an area of cooler sea surface temperatures.[7] Continuing towards the west-northwest, the tropical storm remained consistent in its intensity through the overnight hours of July 4, characterized at the time with a new burst of convection developing atop Bertha's center. Early the following day, satellite imagery revealed a ragged appearance in association with Bertha as it passed over sea surface temperatures near 77 °F (25 °C), values below the threshold needed to sustain a tropical cyclone. However, over the following hours, satellite imagery revealed a slightly better organized Bertha as the system entered an area of warmer sea surface temperatures.
During the afternoon hours of July 6, a series of microwave imagery depicted Bertha's low-level circulation tilted to the southwest of its mid-level center. Additionally, an eye-like feature became apparent, an indication that Bertha was gathering strength. A deep ring of convection surrounded this eye feature, and upper-level outflow spread towards the west. The system continued to intensify over the following hours, and given Bertha's microwave imagery appearance on July 7, the NHC upgraded the system to Category 1 hurricane status on the Saffir–Simpson Hurricane Wind Scale, the first of the season. At this time, the NHC predicted a peak intensity just below Category 2 hurricane status as an approaching trough produces high vertical wind shear began to impede on the system's development after 48 hours. Despite this, Bertha continued to intensify, and began a period of rapid intensification during the afternoon hours of July 7. During this time, Bertha intensified 50 mph (85 km/h) in a 15 hour period. At 5:00 p.m. AST (2100 UTC), Bertha reached its peak intensity as a strong Category 3 hurricane with winds of 125 mph (205 km/h) and a minimum barometric pressure of 952 mbar (hPa; 28.11 inHg).
After reaching peak intensity, satellite imagery revealed a rapid degradation in Bertha's structure. The well-defined eye previously observed had become cloud-filled and ragged, and microwave imagery evidenced that the western portion of the eyewall had eroded. This rapid weakening was likely due to the hurricane encountering an area of higher wind shear, cooler sea surface temperatures, and dry air entrainment. The advisory issued at 1100 a.m. AST (1500 UTC) dropped Bertha's maximum sustained winds to 100 mph (155 km/h), although it was noted that this could be conservative. Further weakening occurred over the next 24 hours as Bertha encountered unfavorable conditions for strengthening. However, after a decrease in wind shear, Bertha intensified to attain Category 2 hurricane status on July 10. While performing a gradual northward turn, Bertha fluctuated in intensity for several days while maintaining hurricane intensity.
By July 13, Bertha had weakened to a tropical storm while located a few hundred miles to the southeast of Bermuda. Turning northward before dipping southeastward, Bertha remained a tropical storm until July 18, at which time it was upgraded to a hurricane once again. It remained at this intensity until unfavorable conditions led to subsequent weakening on July 20. Bertha weakened to a tropical storm and transitioned into an extratropical cyclone shortly after. Its extratropical remnants persisted for the following 24 hours as they moved northeastward into the northern Atlantic, about midday between the island of Newfoundland and the Azore Islands.
As a tropical storm, Bertha dropped rainfall over the southern Cape Verde islands. No damages or deaths were reported.[8]
On July 7, Bermuda residents began purchasing lamps, tarpaulins and flashlights in anticipation of Hurricane Bertha. In the sudden rush, some stores sold out of batteries.[9] Bermuda Public Safety Minister Senator David Burch called a meeting of the island's Emergency Measures Organisation for the night of July 9. He also urged residents to prepare "emergency supply kits" of flashlights and batteries, a first aid kit, nonperishable foods, water and disposable utensils.[10] On July 10 the Department of Parks placed high surf warning signs along the South Shore beaches as Bertha sent strong waves ahead of its path.[11] On July 11 at 11 am AST the Bermuda Weather Service issued a tropical storm watch for the island,[12] and 24 hours later this was raised to a tropical storm warning.[13] On July 13, barricades were erected at all of the island's beaches, which were closed to swimming and watersports.[14]
All flights into and out of Bermuda were disrupted on July 14 as the storm made its final approach to the island. JetBlue and Delta Air Lines canceled their flights while American Airlines executed its flights to Miami and New York a day early, escaping before the tropical storm arrived. British Airways delayed its flight to the afternoon, hoping that the storm would have passed by the time its plane arrives.[14][15] Ferry service to St. Georges was canceled for the whole day,[14] and all other routes outside of Hamilton Harbour were canceled after their morning runs.[16] Some roads flooded, and tree branches were broken around the island. The wind downed power lines, causing scattered power outages, but engineers from the Bermuda Electric Light Company were reattaching cables immediately, even during the height of the storm.[16] Even as Bertha was passing to the east of the island and delivering tropical storm force winds, worries that it might re-strengthen to a hurricane before clearing the island prompted the government of Bermuda to issue a hurricane watch.[17] A total of 4.77 inches (121 mm) of rainfall fell at their international airport.[18]
The hurricane produced strong waves and rip currents along the East Coast of the United States, which caused three deaths along the coastline of New Jersey. On July 12, a 51-year old man died after suddenly losing consciousness during his rescue. On July 13, three men swam out to a buoy about 300 ft (91.4 m) off the coast of Wildwood Beach when they were overcome by the rough surf. One swimmer was found unconscious in the water and pronounced dead at the scene, the second was never found and presumed dead, and the third was rescued. During the event, a total of 57 people had to be rescued along the coast of New Jersey.[19] Three rip currents also caused 55 injuries throughout beaches in Delaware. The injuries ranged from minor scrapes to broken bones.[20] Four people were also injured in North Carolina, one of which nearly drowned as he had aspirated water shortly before a lifeguard rescued him. At least 60 people had to be rescued from the rough seas over a two day span.[21]
Hurricane Bertha holds the records for the longest-lived July Atlantic tropical cyclone at 17 days,[1] the easternmost forming tropical storm, at 24.7°W, easternmost-forming hurricane at 50.2°W, and easternmost-forming pre-August major hurricane at 52.1°W (records all previously held by 1996's Bertha). Bertha is also the sixth strongest pre-August Atlantic tropical cyclone on record and was the third strongest July storm on record, behind Dennis and Emily of 2005.[22] Additioanlly, Bertha was the longest-lived tropical cyclone in the Atlantic Basin since Ivan in 2004.[23] The system produced 4.77 inches (121 mm) of rainfall on the island of Bermuda, making it the 10th wettest storm in recorded history at that location.[24]
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Tropical cyclones of the 2008 Atlantic hurricane season |
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