This article is about the 2008 hurricane. For other storms of the same name, see Hurricane Bertha. Hurricane Bertha was a rare early season Cape Verde-type hurricane. It is both the longest-lived July Atlantic tropical cyclone on record,[1] and the easternmost forming July tropical storm on record. [2] The second named storm of the 2008 Atlantic hurricane season, Bertha developed from a tropical wave that emerged off the coast of Africa on July 1. Tropical Depression Two formed about 250 miles (405 km) south of Cape Verde. The system quickly strengthened into Tropical Storm Bertha on July 3. Bertha moved westward over the next few days as a weak tropical storm. Late on July 6, Bertha began to strengthen well to the east of the Northern Leeward Islands. Bertha continued to strengthen and became the first hurricane of the season on July 7, as well as the first major hurricane, later that day. The hurricane weakened during the day on July 8, due to a nearby upper level low to its northeast. Thereafter, it drifted north-northwest towards Bermuda before slowly looping to its southeast on July 12 and July 13. The system moved within 40 miles (64 km) of Bermuda on July 14 before moving northeast away from the island. On July 16, Bertha curved back to the southeast due to the influence of a deep cyclone to its east, and then turned northeast, reaching hurricane strength before becoming extratropical on July 20.
Storm history
Early on July 1, a strong and large tropical wave emerged off the coast of Africa.[3] By early the next day, a surface low developed and the wave became better organized.[4] The National Hurricane Center upgraded the system to Tropical Depression Two in the morning hours of July 3 after the system was able to maintain convection over its center for at least 12 hours.[5] The depression organized further and developed two distinct bands of convection. Six hours after becoming a depression, it was upgraded to Tropical Storm Bertha, the second named storm of the season.[6] The National Hurricane Center noted that this tropical cyclone was remarkably forecasted up to a week in advance by many global computer models.[5]
Bertha continued on a westward motion as the storm moved under a ridge of high pressure.[7] Despite low wind shear, Bertha remained a weak tropical storm due to cool sea surface temperatures.[7] Over the next few days, the system started to move over warmer waters again, while moving west at over 25 mph (40 km/h). [8] Bertha began to strengthen on July 6 as microwave images showed a developing eye-like feature.[9] Intensification continued into the morning of July 7 when Tropical Storm Bertha strengthened into a hurricane, the first of the season.[10] The deepening later became more rapid, and Bertha strengthened into a Category 3 hurricane late that afternoon.[11] Later in the evening, the National Hurricane Center said that Bertha may have been stronger than 115 mph (185 km/h) between 3 p.m. EDT (1900 UTC) and 5 p.m. EDT (2300 UTC) that evening as objective intensity estimates were at about 135 mph (215 km/h).
On July 8 Bertha began to quickly weaken under increasing wind shear and was downgraded to a Category 2 hurricane later in the morning. Bertha continued to weaken that afternoon and was downgraded to a Category 1 hurricane in the late afternoon, but re-intensified to Category 2 the next day. However, on July 10 Bertha was again downgraded to a Category 1 hurricane as an eyewall replacement cycle had begun. Movement slowed as steering currents collapsed, and by July 12, Bertha was stationary south-southeast of Bermuda. After barely moving for a full day, Bertha caused an upwelling of cold water which significantly cooled the sea surface temperature beneath it. This cooler water then weakened the hurricane down to strong tropical storm strength.[12] On July 14 Bertha passed within about 40 miles (64 km) of Bermuda.[13] After moving off to Bermuda's northeast, a deep cyclone east of Bertha forced the tropical cyclone on a southeasterly track on July 16. On July 18, Bertha strengthened up to Category 1 hurricane strength on the SSHS scale. [14] On July 20, Bertha became extratropical, and the final advisory (Advisory 70), was written at 11 a.m. EST that day. Bertha lasted as a tropical system for 17 days, the longest lasting storm since Hurricane Ivan in 2004.
Preparations
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.[15] 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.[16] 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.[17] On July 11 at 11 a.m. AST the Bermuda Weather Service issued a tropical storm watch for the island,[18] and 24 hours later this was raised to a tropical storm warning. [19] On July 13 barricades were erected at all of the island's beaches, which were closed to swimming and watersports.[20]
Impact
As a tropical storm, Bertha dropped rainfall over the southern Cape Verde islands. No damages or deaths were reported.[28]
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 flew its Miami and New York flights 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.[20][29] Ferry service to St. Georges was canceled for the whole day,[20] and all other routes outside of Hamilton Harbour were canceled after their morning runs.[30] 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.[30]
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.[31] A total of 4.69 inches (119 mm) of rainfall fell at their international airport.[32]
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.[33]
Records
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. 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.[34] Bertha became the longest-lived July Atlantic tropical cyclone on record, and is also the longest-lived tropical cyclone in the Atlantic Basin since Ivan in 2004.[35] It was also the first "B" storm to reach hurricane strength since Hurricane Bret in 1999.
See also
References
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