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วันอังคารที่ 4 กันยายน พ.ศ. 2550

Hurricane Felix (2007)

Hurricane Felix is the sixth named storm, second hurricane, and second Category 5 hurricane of the 2007 Atlantic hurricane season. Forming from a tropical wave on August 31, it passed through the southern Windward Islands on September 1 before strengthening to attain hurricane status. A day later on September 2, Felix rapidly strengthened into a major hurricane, and early on September 3 it was upgraded to Category 5 status; by 2100 UTC on September 3 the hurricane was downgraded to Category 4 status, but was re-upgraded by 1040 UTC to a Category 5 hurricane. Felix is currently making landfall just south of the border between Nicaragua and Honduras.

Storm history

A tropical wave moved off the coast of Africa on August 24, tracking westward at around 14 mph (23 km/h) with no associated deep convection and a weak low-level inverted-V curvature.[1] Initially difficult to locate on satellites,[2] the wave axis tracked through a moist environment[3] and developed an area of scattered thunderstorms. By August 25 visible satellite imagery indicated broad cyclonic turning just north of the Intertropical Convergence Zone.[4] The wave continued to develop moderate to strong convection, and on August 27 a 1012 mbar low pressure area developed about 830 miles (1,340 km) west-southwest of Praia, Cape Verde.[5] For the next several days the system failed to organize significantly;[6] however, on August 30 the wave became better defined with more representation of the cyclonic turning into the low.[7] Convection increased early the next day,[8] and a Hurricane Hunters flight into the system reported the presence of a closed low-level circulation; accordingly, the National Hurricane Center initiated advisories on Tropical Depression Six at 2100 UTC on August 31 while it was located about 180 miles (295 km) east-southeast of the southern Windward Islands.[9]
Upon becoming a tropical cyclone, the depression was located to the south of a strong ridge, resulting in a west-northwest motion. The system maintained curved rainbands with expanding outflow, and with light wind shear and warm water temperatures the environment favored further development.[9] Its deep convection consolidated very near the center, and shortly after passing over the island of Grenada the depression intensified into Tropical Storm Felix early at around 0900 UTC on September 1.[10] Felix quickly strengthened as it developed a small inner core of convection with tightly-wound bands around the center,[11] and by late on September 1 an eye feature was observed on satellite imagery.[12] Based on reports from reconnaissance aircraft, the National Hurricane Center estimated that Felix attained hurricane status by early on September 2 while located about 155 miles (250 km) east-northeast of Bonaire.[13]
Tracking through an area of extremely low wind shear and increasingly high oceanic heat content, Hurricane Felix quickly developed a well-defined eye, a symmetric cloud structure, and strong upper-level outflow.[14] Felix was upgraded to major hurricane status at around 1800 UTC on September 2 while located about 490 miles (790 km) southeast of Kingston, Jamaica.[15] Rapid strengthening continued, and later that day the hurricane attained Category 4 status on the Saffir-Simpson Hurricane Scale with the pressure dropping to 957 mbar; this corresponded to a falling rate of 3.4 mbar per hour, which the National Hurricane Center remarked as "one of the more rapid deepening rates we have observed." A Hurricane Hunters flight reported a stadium effect in the eye, and also reported the eye diameter shrank to 14 miles (22 km).[16] A subsequent Hurricane Hunters flight experienced flight level winds of 175 mph (280 km/h), with peak surface winds of 163 mph (263 km/h) reported in the southwest quadrant of the eyewall; surface winds of up to 189 mph (306 km/h) were found in its northeastern quadrant, although the National Hurricane Center reported the peak reading could have been contaminated due to graupel in the clouds. Based on the observations, it is estimated Felix attained winds of 165 mph (265 km/h) by 0000 UTC on September 3 while located about 390 miles (625 km) southeast of Kingston, Jamaica, making Felix a Category 5 hurricane on the Saffir-Simpson Hurricane Scale. While investigating the hurricane, Hurricane Hunters encountered extreme turbulence and potentially dangerous graupel, which forced the flight to abort the mission.[17]
Continuing quickly westward, the eye of Felix diameter decreased to 12 miles (19 km), and the National Hurricane Center estimates the hurricane attained a minimum central pressure of 929 mbar about nine hours after it reached Category 5 status.[18] Subsequently, cloud tops near the center began to warm as the eye became less distinct,[19] and by 1800 UTC on September 3 Felix weakened to Category 4 status with winds of 145 mph (235 km/h).[20] On September 4, Felix had completed an eyewall replacement cycle and began strengthening again during the day.[21] Felix was upgraded to a Category 5 for the second time at 1040 UTC,[22] and made landfall in extreme north-eastern Nicaragua shortly after.[23]

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