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Hurricane Rick is the third-most intense Pacific hurricane on record. Developing south of Mexico on October 15, 2009, Hurricane Rick traversed an area favoring rapid intensification, allowing it to become a hurricane within 24 hours of being declared a tropical depression. An eye began to form during the afternoon of October 16; once fully formed, the storm underwent another period of rapid strengthening. During the afternoon of October 17, the storm attained Category 5 status on the Saffir–Simpson hurricane wind scale. Several hours later, Rick attained its peak intensity as the third-strongest Pacific hurricane on record with winds of and a barometric pressure of 906 mbar (hPa; 26.75 inHg). After maintaining this intensity for several hours, Rick began to weaken in response to a combination of an eyewall replacement cycle and increasing wind shear. By October 19, the storm was downgraded to a Category 3 hurricane and the following day to a tropical storm. The long-anticipated northeast turn took place near the end of this phase, also accompanied by a brief decrease in forward motion. On October 21, Rick quickly moved northeast, brushing the tip of Baja California Sur before making landfall near Mazatlán with winds of . Several hours after moving inland, the final advisory from the NHC was issued as the storm weakened to a tropical depression and dissipated. Prior to landfall, the National Hurricane Center (NHC) initially forecast Rick to make landfall in southern Baja California as a high-end Category 2 hurricane, prompting hurricane watches. Officials ordered several hundred residents to evacuate from low-lying areas, although tropical storm warnings replaced the hurricane watches after the storm had weakened. Overall, the damage from Rick was significantly less than initially anticipated. In Mexico, three people were killed by the storm, one in Oaxaca and two in Baja California Sur. ==Meteorological history== Hurricane Rick originated from a strong tropical disturbance wave that moved off the west coast of Africa on October 3, 2009. Convective activity was initially sparse as the system tracked westward across the Atlantic Ocean. By October 8, an area of low pressure developed within the disturbance wave and convection increased. The low eventually moved over South America and dissipated on October 11. The wave, however, remained well-defined and continued westward, entering the Pacific Ocean on October 12. By the morning of October 15, the wave began to regain convection and eventually spawned a new area of low pressure roughly south-southwest of Puerto Ángel, Mexico. By the afternoon, the NHC reported that the system had become increasingly organized and was likely to develop into a tropical depression later that day. Around 11:00 am PDT (1800 UTC), the NHC declared that the low had developed into a tropical depression, the 20th of the 2009 Pacific hurricane season.〔 The storm featured well-developed outflow in all directions. Environmental conditions consisting of low wind shear, high moisture content and above average sea surface temperatures in the path of the system were exceptionally favorable for rapid development. Additionally, the storm was being steered through this region by a low- to mid-level ridge over Mexico. Six hours after being declared a depression, the system quickly intensified into a tropical storm, at which time it was given the name Rick. Deep convection, an early indication of an eye forming, had begun wrapping around the center of the system. Early on October 16, a ragged eyewall began to develop and several hours later, Rick intensified into a Category 1 hurricane with winds of . The rapid intensification was fueled by waters of , several degrees above average.〔 By the evening of October 16, microwave satellite imagery depicted a well-defined eye; however, this feature was not present on infrared images. Despite this, the NHC upgraded Rick to a Category 2 hurricane with winds now reaching . Early the next morning, the storm intensified into a major hurricane, a storm that ranks as a Category 3 or higher on the Saffir–Simpson Hurricane Scale. The eye was clearly visible on satellite images and deep, very cold convection surrounded it, signifying a powerful cyclone. Less than 40 minutes after this upgrade, the NHC issued a special advisory stating that Rick had further strengthened into a Category 4 hurricane. Continuing to gain strength, Rick attained winds of several hours later on October 17. A possible outer eyewall, a second eye larger than the first that often forms at the beginning of an eyewall replacement cycle, was noted at this time. The eye of the storm became very well-defined and nearly cloud free, measuring roughly in diameter. In addition to the rapid intensification, Rick was also growing in size. By the afternoon hours, tropical storm-force winds extended up to from the center of the storm, with a maximum gale diameter of . At 3:10 pm PDT (2210 UTC), the NHC issued its second special advisory for Rick, this time stating that the storm had become a Category 5 hurricane, the first in the basin since Hurricane Kenna in 2002. Around 8:00 pm PDT (0300 UTC on October 18), Rick attained its peak intensity as the third-strongest Pacific hurricane on record. Maximum sustained winds in the eyewall reached and the barometric pressure is estimated to have bottomed out at . The pressure was not directly measured as reconnaissance missions by Hurricane Hunter aircraft were not done because the storm was too far from land. Lixion Avila, a senior hurricane specialist at the NHC, described Rick's satellite presentation at this time as "spectacular." Rick maintained its peak intensity for roughly two hours between 7:00 pm and 9:00 pm PDT (0200 and 0400 UTC) on October 17, before it began to weaken in response to an eyewall replacement cycle and increasing wind shear. By the afternoon of October 18, the storm had weakened to a low-end Category 5 hurricane, with maximum winds of . Deep convection around the eye warmed slightly and a combination of dry air and wind shear restrained the extent of the storms' outflow to the west. Later that day, Rick began to turn towards the northwest as the subtropical ridge north of the system began to weaken. Early on October 19, Rick was downgraded to a Category 3 hurricane as it began its approach to the southern end of the Baja California peninsula. Wind shear and dry air quickly entered the core of the system, with the eye disappearing from satellite imagery later that morning.〔 During the evening of October 19, the center of Rick became devoid of convective activity, resulting in the NHC downgrading it to a tropical storm. According to meteorologists at the NHC, the weakening was "...almost as fast as it strengthened several days ago." The first Hurricane Hunter reconnaissance mission into the storm took place during the afternoon of October 20. During the mission, sustained winds of and a surface pressure of were recorded. Several hours after this, convection rapidly increased, with a large area of deep convection developing northeast of the center of circulation; however, this was not associated with intensification. Around 7:00 am PDT (1400 UTC) on October 21. Tropical Storm Rick made landfall near Mazatlán with winds of 60 mph (95 km/h).〔 Following landfall, the storm rapidly weakened to a tropical depression and roughly seven hours after moving inland, the surface circulation of Rick dissipated over the high terrain of Mexico. 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 Rick (2009)」の詳細全文を読む スポンサード リンク
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