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Hurricane Fred was the first hurricane to move through the Cape Verde Islands since 1892. The second hurricane and sixth named storm of the 2015 Atlantic hurricane season, Fred originated from a well-defined tropical wave over West Africa in late August. Once offshore, the wave moved northwestward within a favorable tropospheric environment and strengthened into a tropical storm on August 30. The next day, Fred further grew to a Category 1 hurricane with peak winds of 85 mph (140 km/h) as it approached Cape Verde. After passing Boa Vista and moving away from Santo Antão, it entered a phase of steady weakening, dropping below hurricane status by September 1. Fred then turned to the west-northwest and endured increasingly hostile wind shear, but maintained its status as a tropical cyclone despite repeated forecasts of dissipation. It fluctuated between a minimal tropical storm and tropical depression through September 4–5 before curving sharply to the north. By September 6, Fred's circulation pattern had diminished considerably, and the National Hurricane Center discontinued its public advisories on the storm. At the threat of the hurricane, all of Cape Verde was placed under a hurricane warning for the first time in history. Gale-force winds battered much of the Barlavento region through August 31, downing numerous trees and utility poles. On the easternmost islands of Boa Vista and Sal, Fred leveled roofs and left several villages without power and phone services for several days. About 70 percent of the houses in Povoação Velha were damaged to some degree. Throughout the northern islands, rainstorms damaged homes and roads, and São Nicolau lost large amounts of its crop and livestock. Monetary losses exceeded $1.1 million (2015 USD) across Cape Verde, though the rain's overall impact on the agriculture was positive. Swells from the hurricane produced violent seas along West African shores, destroying fishing villages and submerging large swaths of residential area in Senegal. Between the coasts of West Africa and Cape Verde, maritime incidents related to Fred resulted in 9 deaths. ==Meteorological history== Early on August 28, the National Hurricane Center (NHC) began monitoring a tropical wave—an elongated area of low air pressure—inland over West Africa. Traced by widespread cloudiness, the wave tracked toward the open Atlantic throughout the remainder of the day. A broad cyclonic rotation began to develop within the lower atmosphere on August 29, near the Guinea coastline. The disturbance veered toward the northwest and emerged offshore near Conakry around 18:00 UTC that day. By then, the NHC predicted a favorable environment for tropical cyclone development within the next 48 hours. Heavy thunderstorms thrived overnight, and consolidated near a well-defined low-pressure center. On the morning of August 30, satellite images and scatterometer data confirmed that a tropical depression had formed about 190 mi (310 km) west of Bissau, with wind speeds of 35 mph (55 km/h). Although tropical cyclones in the extreme eastern Atlantic are normally propelled westward by high pressure from the subtropical ridge, this depression moved toward the northwest, along a breach in the ridge caused by another disturbance.〔 Its cyclonic structure steadily improved: a sharply curved rainband tightened around the center, resembling the precursor to an eye. At 09:00 UTC on August 30, the depression was upgraded to Tropical Storm Fred about 405 mi (650 km) east-southeast of the southern Cape Verde Islands—one of the four easternmost locations for a tropical storm since modern record-keeping began in 1851. Intensification trends continued at a steady pace while Fred trekked through a region with ample tropical moisture, light upper winds, and above-average sea surface temperatures; the storm developed a thick, circular central dense overcast with good outflow, and the eye feature became well established at all levels of the circulation. Based on a combination of these characteristics and satellite estimates of 75 mph (120 km/h) winds, Fred was upgraded to a Category 1 hurricane at 06:00 UTC on August 31.〔 Then centered 60 mi (110 km) south-southeast of Rabil, Boa Vista, it was the easternmost tropical cyclone ever to attain hurricane status in the tropical Atlantic. A compact cyclone, Fred quickly reached its peak intensity with a minimum central pressure of 986 mbar (hPa; 29.12 inHg) and 85 mph (140 km/h) winds. Through the rest of August 31, the hurricane traversed the Barlavento Islands of Cape Verde. The eye barely skirted the southern coast of Boa Vista around 12:00 UTC,〔 decreasing in definition over the next 12 hours as it passed north of São Nicolau and then north-northeast of Santo Antão. On September 1, drier air and increasing wind shear aloft dispersed the inner convection, which caused Fred to weaken to a tropical storm. Rebuilding high pressure to the north over the eastern Atlantic turned the weakening storm slightly toward the west-northwest over considerably cooler waters. Through much of September 1–4, convection was limited to intermittent flare-ups, with the associated thunderstorms continuously blown away from the center by the strong upper winds. Despite the adverse environment and its lack of stable convection, Fred retained a robust spiral of low-level clouds and gales during this period, defying the NHC's repeated forecasts of its dissipation.〔 * *〕 Around 15:00 UTC, September 4, a waning wind circulation prompted the NHC to downgrade Fred to a tropical depression; though its winds briefly reincreased to tropical storm force the next day, it continued as a depression with minimal convection throughout the remainder of its existence.〔 * *〕 Concurrently, a deep-altitude disturbance a few hundred miles east of Bermuda began to erode the southern edge of the high-pressure ridge that Fred had circumnavigated for most of its journey. This changed the steering pattern in the region, turning the depression abruptly to the north on September 6.〔 Over the following hours, Fred became increasingly indistinguishable as a result of its progressively worsening surroundings. It officially lost its status as a tropical cyclone at 21:00 UTC, about 1,200 mi (1,935 km) southwest of the Azores. 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 Fred (2015)」の詳細全文を読む スポンサード リンク
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