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Hurricane Ioke, also referred to as Typhoon Ioke, was the most intense hurricane ever recorded in the Central Pacific. The first storm to form in the Central Pacific in the 2006 Pacific hurricane season, Ioke was a record breaking, long-lived and extremely powerful storm that traversed the Pacific for 17 days, reaching the equivalent of Category 5 status on the Saffir-Simpson Hurricane Scale three times. The cyclone developed from the Intertropical Convergence Zone on August 20 far to the south of Hawaii. Encountering warm waters, little wind shear, and well-defined outflow, Ioke intensified from a tropical depression to Category 4 status within 48 hours. Late on August 22 it rapidly weakened to Category 2 status before crossing over Johnston Atoll. Two days later favorable conditions again allowed for rapid strengthening, and Ioke attained Category 5 status on August 25 before crossing the International Date Line. As it continued westward its intensity fluctuated, and on August 31 it passed near Wake Island with winds of . Ioke gradually weakened as it turned northwestward and northward, and by September 6 it had transitioned into an extratropical cyclone. The remnants of Ioke accelerated northeastward and ultimately crossed into Alaska. Ioke did not affect any permanently populated areas in the Central Pacific or Western Pacific basins as a hurricane or a typhoon. A crew of 12 people rode out the hurricane in a hurricane-proof bunker on Johnston Atoll; the crew estimated winds reached over , which damaged trees on the island but did not impact the island's bird population. The typhoon left moderate damage on Wake Island totaling $88 million (2006 USD), including blown off roofs and damaged buildings, though the infrastructure of the island was left intact; all military personnel were evacuated from the island. Later, the extratropical remnants of Ioke produced a severe storm surge along the Alaskan coastline, causing beach erosion. == Meteorological history == The Intertropical Convergence Zone (ITCZ) spawned a tropical disturbance with a low-level circulation far to the southeast of Hawaii in the middle of August 2006. Under the influence of a strong westward-moving subtropical ridge to its north, the disturbance tracked nearly due westward, with deep convection in the region increasing and decreasing on a daily basis. It slowly became better organized, and early on August 20 the disturbance developed into Tropical Depression One-C while located about south of Honolulu, Hawaii. At the time, there was no convection associated with the ITCZ within 10° Longitude. With wind shear practically non-existent and sea surface temperatures of around , conditions favored strengthening,〔 and operationally the cyclone was forecast to reach minimal hurricane status within four days before beginning to weaken. The depression attained tropical storm status within six hours of developing.〔 The Central Pacific Hurricane Center designated the system with the name ''Ioke'' , Hawaiian for the name Joyce. Subsequently, Ioke quickly strengthened, and by late on August 20 the storm developed a central dense overcast and the beginnings of an eyewall; early on August 21 the storm intensified into a hurricane, just 24 hours after first developing.〔 Hurricane Ioke steadily deepened as it continued west-northwestward, with better definition of the eye and deepening of the eyewall convection. Near the International Date Line a frontal trough turned the hurricane to the northwest, and after a period of rapid deepening Ioke attained winds of early on August 22 while located about southeast of Johnston Atoll. After maintaining Category 4 status on the Saffir-Simpson Hurricane Scale for about 18 hours,〔 southwesterly wind shear slightly disrupted the inner core of the hurricane, and Ioke quickly weakened to winds of about . Late on August 22, the hurricane passed about south of Johnston Atoll,〔 with the northeastern portion of the eyewall crossing the atoll early on August 23. After turning westward later in the day, wind shear began to decrease, allowing a second period of rapid deepening. By August 24 the hurricane maintained a closed eyewall, and on August 25 Ioke attained Category 5 status on the Saffir-Simpson Hurricane Scale while located about west-southwest of the Hawaiian Island of Kauai.〔 After maintaining Category 5 status for about 18 hours,〔 Hurricane Ioke weakened slightly due to an eyewall replacement cycle. Completing the cycle on August 26, the hurricane restrengthened to Category 5 status. The trough to its west tracked further away from the hurricane, allowing the subtropical ridge to build ahead of the hurricane which turned Ioke to the southwest.〔 The overall environment remained very favorable for sustainment of the powerful cyclone. Strong upper-level cyclones far to its northwest provided outflow channels and light wind shear, with warm water temperatures along its path.〔 With the conditions, the Geophysical Fluid Dynamics Laboratory hurricane model predicted Ioke to reach winds of , with a predicted minimum pressure of 860 mbar (hPa). Early on August 27, the pressure dropped to 915 mbar (hPa), and shortly thereafter Ioke crossed the International Date Line, becoming a typhoon.〔 Unofficially referred as a super typhoon by the Joint Typhoon Warning Center (JTWC), Ioke remained at the equivalence of a Category 5 hurricane for about 12 hours after crossing the Date Line. It then began a slight weakening trend on August 28, due to increased inflow from the ridge to its north. On August 29, the cyclone turned to the west and west-northwest while tracking around the periphery of the subtropical ridge, and Ioke again reached the equivalence of Category 5 status.〔 The Japan Meteorological Agency (JMA) assessed Ioke as attaining peak 10 minute sustained winds of on August 30. Later that day, the typhoon weakened to the equivalent of a Category 4 hurricane for the final time, and on August 31 Ioke passed very near Wake Island with winds of about .〔 By September 1, increased wind shear and drier air caused the eye of Ioke to become cloud-filled and elongated, and by September 2 Ioke was undergoing another eyewall replacement cycle. On September 2, Ioke passed about north of Minami Torishima with winds of about . Gradual weakening continued, and the typhoon steadily shifted its track to the northwest around the subtropical ridge. A deepening trough turned Ioke to the north-northwest and north, and the cyclone weakened to a tropical storm a few hundred miles east of Japan. After accelerating northeastward, the cyclone began losing tropical characteristics, and the JTWC declared Ioke as an extratropical cyclone on September 5.〔 The JMA maintained Ioke as a typhoon until a day later, and maintained Ioke as a tropical cyclone until it was declared extratropical midday on September 6. The extratropical remnants of Ioke were tracked by the JMA until September 7 when it was located near the Aleutian Islands of Alaska.〔 The storm deepened as it approached the Aleutians, and re-developed winds of hurricane-force. It entered the Bering Sea on September 8, and after turning eastward crossed the Aleutian Islands and entered the Gulf of Alaska. The extratropical remnants of Ioke dissipated near southeastern Alaska on September 12. 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 Ioke」の詳細全文を読む スポンサード リンク
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