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billion ( USD) | affected = Grady, McClain, Cleveland and Oklahoma counties in Oklahoma; with the worst impacts occurring in the towns/cities of Bridge Creek, Moore, Southwest Oklahoma City, Del City, and Midwest City | location = | current advisories = | enhanced = | notes = Part of the 1999 Oklahoma tornado outbreak }} The 1999 Bridge Creek–Moore tornado was an extremely powerful F5 tornado in which the highest wind speeds ever measured globally, , were recorded by a Doppler on Wheels (DOW) radar. The tornado devastated southern portions of Oklahoma City, Oklahoma, along with surrounding suburbs and towns during the early evening of May 3, 1999. Throughout its 85-minute existence, the tornado covered , destroying thousands of homes, killing 36 people (plus an additional five indirectly), and leaving US$1 billion in damage, ranking it as the fifth-costliest on record, not accounting for inflation. The tornado first touched down at 6:23 p.m. Central Daylight Time (CDT) in Grady County, roughly south-southwest of Amber. It quickly intensified into a violent F4, and gradually reached F5 status after traveling , at which time it struck the community of Bridge Creek. Once it moved through the unincorporated community, it fluctuated in strength, ranging from F2 to F5 status before it crossed into Cleveland County. Not long after entering the county, it reached F5 intensity for a third time as it moved through the city of Moore. By 7:30 p.m. CDT, the tornado crossed into Oklahoma County and battered southeastern Oklahoma City, Del City and Midwest City, before dissipating around 7:48 p.m. CDT just outside of Midwest City. In terms of structural losses, a total of 8,132 homes, 1,041 apartments, 260 businesses, 11 public buildings and seven churches were damaged or destroyed. In the wake of the tornado, large-scale search and rescue operations took place in the affected areas. A major disaster declaration was signed by President Bill Clinton the following day (May 4), allowing for the state to receive federal aid. In the following months, disaster aid amounted to $67.8 million. In light of the fatalities that occurred under highway overpasses, the notion of them being safe areas to seek shelter was dismissed, and they were from then on considered to be one of the most dangerous places to be during a tornado. Reconstruction projects in subsequent years led to a safer, tornado-ready community. In May 2013, similar areas adjacent to the 1999 storm's track were again devastated by an EF5 tornado, but there were fewer fatalities from that event despite inflicting structural damage similar in severity to the 1999 event. ==Meteorological synopsis== The Bridge Creek–Moore tornado was part of a much larger outbreak, which spawned 71 tornadoes across five states throughout the Central Plains on May 3 alone, along with an additional 25 that touched down on May 4 in some of the areas affected by the previous day's activity (some of which were spawned supercells that developed on the evening of May 3), stretching eastward to the Mississippi River Valley. On the morning of May 3, in its Day 1 Convective Outlook for the United States, the Storm Prediction Center (SPC) issued a slight risk for severe weather, as a dry line that stretched from western Kansas into western Texas approached a warm, humid air-mass over the Central Plains; the conditions ahead of the dry line and a connecting trough positioned over northeastern Colorado appeared to favor the development of thunderstorms later that day that would contain large hail, damaging straight-line winds and isolated tornadoes. Forecasters at the SPC initially underestimated the atmospheric conditions that would support tornadic development that afternoon and evening; around 4:00 a.m. CDT, Doppler radar and wind profile data indicated a jet streak along the border of California and Nevada, with weather balloon soundings sent up the previous evening by National Weather Service offices in the western United States and numerical computer model data failing to detect the fast-moving air current as it moved ashore from the Pacific Ocean. In addition, the dry line was diffused, with surface winds behind and ahead of the boundary moving into the region from a southerly direction. SPC meteorologists began to recalculate model data during the morning to account for the stronger wind profiles caused by the jet streak; the data acknowledged that thunderstorms would occur within the Central Plains, but disagreed on the exact area of greatest severe weather risk.〔 By 7:00 a.m. Central Daylight Time, CAPE values began exceeding 4,000 j/kg, a level which climatologically favors the development of severe thunderstorms. Despite conflicting model data on the specified area where thunderstorms would develop, the newly available information that denoted a more favorable severe thunderstorm setup in that part of the state prompted the SPC to upgrade the forecasted threat of severe weather to a moderate risk for south-central Kansas, much of the western two-thirds of Oklahoma, and northwestern and north-central Texas at 11:15 a.m. CDT that morning, which now indicated an elevated threat of strong tornadoes.〔 By the early afternoon hours, forecasters at both the SPC and the National Weather Service Weather Forecast Office in Norman, Oklahoma realized that a major event was likely to take place based solely on observational data from radar and weather satellite imagery and balloon soundings, as the computer models remained uncooperative in helping meteorologists determine where the greatest threat of severe storms would occur.〔 Conditions became highly conducive for tornadic development by 1:00 p.m. CDT as wind shear intensified over the region (as confirmed by an unscheduled balloon sounding flight conducted by the NWS Norman office), creating a highly unstable atmosphere. The sounding balloon recorded winds blowing southwesterly (at and , respectively) at the surface and at the level, southerly winds of at and westerly winds of at ; it also indicated that a capping inversion over the region was weakening in southwestern Oklahoma and north Texas; with the warm air above the surface cooling down, this allowed warm air at the surface the chance to rise and potentially create thunderstorms.〔〔 Although cirrus clouds − a bank of which had developed in west Texas and overspread portions of Oklahoma later in the morning − were present through much of the day, an area of clearing skies over western north Texas and southwestern Oklahoma early that afternoon allowed for the sun to heat up the moisture-laden region, creating significant atmospheric instability.〔 At 3:49 p.m. CDT, a high risk of severe weather was issued by the Storm Prediction Center for much of central Oklahoma. Within 25 minutes of this, the National Weather Service office in Norman issued a severe thunderstorm warning for Comanche County by 4:15 p.m. CDT late that afternoon, as the first storm of the event rapidly intensified. A half-hour later at 4:45 p.m. CDT, the Storm Prediction Center issued a tornado watch for western and central Oklahoma, for the threat of tornadoes, hail up to in diameter and wind gusts to .〔 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「1999 Bridge Creek–Moore tornado」の詳細全文を読む スポンサード リンク
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