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Hurricane Gert was the fourth of five major hurricanes in the moderately active 1999 Atlantic hurricane season. A Cape Verde-type hurricane, Gert formed on September 11 off the coast of Africa before heading west-northwest. It reached a peak wind speed of 150 mph (240 km/h) by September 15 over the open central Atlantic east-northeast of the Leeward Islands. It gradually curved to the northwest and later to the north, due to a weakness in the subtropical ridge created by Hurricane Floyd. Hurricane Gert passed east of Bermuda on September 21 and began a steady weakening trend at that time. It turned to the northeast, and on September 23, Gert transitioned into an extratropical cyclone to the southeast of Atlantic Canada before being absorbed by a larger storm. For several days, Gert threatened to strike Bermuda, prompting the evacuation of tourists. Although Gert's center did not make landfall, it passed a short distance east of the island, producing hurricane force winds that left 11,000 people without power. High waves swept two people out to sea at Acadia National Park in Maine. Later, strong waves struck Newfoundland and left heavy marine damage. ==Meteorological history== A tropical wave moved off the coast of Africa on September 10, with evidence of a low-level circulation and convective banding. It moved west-northwestward, located south of a subtropical ridge. Based on satellite imagery, it is estimated the system organized into Tropical Depression Nine by 1200 UTC on September 11 to the south of the Cape Verde islands. Upon its formation, the center was poorly defined, with restricted easterly outflow due to easterly wind shear. After about 24 hours of remaining somewhat disorganized, the convection became more concentrated on September 12 as banding features and outflow improved. Consequently, the National Hurricane Center (NHC) upgraded the depression to Tropical Storm Gert, the seventh named storm of the season. After becoming a tropical storm, Gert quickly intensified due to the presence of an anticyclone aloft, as well as warm water temperatures exceeding 84 °F (29 °C). Following the development of a warm spot near the center, Gert intensified into a hurricane on September 13.〔 It strengthened further, developing an eye that briefly dissipated before reforming. Early on September 15, Gert attained major hurricane strength, or a Category 3 on the Saffir-Simpson scale.〔 Still moving west-northwestward, Gert continued its steady intensification trend, developing well-defined outflow throughout the circulation that was described as "outstanding". After reaching Category 4 status on September 15, Gert strengthened further to peak winds of early on September 16, as estimated on satellite imagery through the Dvorak technique. Satellite intensity estimates reached as high as , or a Category 5 hurricane. At the time, the hurricane was located about 720 mi (1160 km) east-northeast of Guadeloupe in the Lesser Antilles.〔 Around the time of peak intensity, Gert maintained a round central dense overcast. Hurricane Hunters investigated the hurricane on September 16 and indicated a slight weakening trend due to an eyewall replacement cycle. Gradually Gert turned toward the northwest due to a weakness in the subtropical ridge, created by Hurricane Floyd to the west. As it did so, the hurricane re-intensified briefly before resuming a weakening trend,〔 due to increased wind shear and an upper-level trough to its west restricting outflow. After weakening to winds of , Gert again re-strengthened to Category 4 status on September 19,〔 as the eye became well-organized within its surrounding convection following an eyewall replacement cycle. By September 20, while the hurricane was approaching Bermuda, the appearance became more ragged due to the intrusion of unfavorable dry air. Early on September 21 Gert weakened to Category 2 intensity, around the same time it turned northward. Later that day it passed about east of Bermuda, producing hurricane force winds on the island.〔 Steady weakening continued as Gert accelerated northeastward under the influence of an approaching trough. The convection decreased around the center due to cooler water temperatures, and on September 23 Gert weakened to tropical storm status as it approached Newfoundland.〔 After nearly all of the convection had dissipated, the system no longer met the characteristics of a tropical cyclone. As a result, it was declared extratropical at 1200 UTC on September 23 about 55 mi (90 km) southeast of Cape Race, Newfoundland. About six hours later, the remnants of Gert were absorbed by a larger extratropical storm.〔 Gert was the fourth of five Category 4 hurricanes to form during the 1999 season, the highest number of such storms on record. Later, the 2005 season tied the record. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Hurricane Gert (1999)」の詳細全文を読む スポンサード リンク
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