夢蝶葬花/龙卷风
在世界的一些地方，特别是在美国，龙卷风可以对旅行者构成威胁。
理解
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龙卷风是一个旋转的极低压空气柱，它向内和向上吸收周围的空气。它们会产生强风（通常为100-200英里/小时），并且可以将重物举到空中，并在龙卷风移动时将其也跟着漂移。它们开始是从暴风云中下降的漏斗状物，当它们接触到地面时就变成了“龙卷风”。与飓风不同，龙卷风发展非常迅速，几乎不会提前发出预警（最多几分钟），但它们的寿命也非常短，同样每次只持续几分钟。它们经常成群出现，几个龙卷风几乎同时袭击一个地区。
与气旋（飓风或台风）相比，龙卷风更加集中，密度也要大得多。虽然飓风的直径通常至少跨越几十英里，甚至上百英里，但龙卷风通常只有一英里也是很罕见的。
据报道，美国每年大约有1000场龙卷风，但是只有其中的一小部分着落并袭击建筑物。此外，只有不到30%的龙卷风是相当强大的（EF2+）。大多数死亡情况都发生在一栋房屋或者汽车上。无论设么时候龙卷风都有可能发生，但主要还是分布在春季和初夏的雷雨天气里。请记住，作为一个短期的游客，无论您在何时何地旅行，在错误的时间和错误的地点出现龙卷风的概率都是很小的，但无论如何，都请您最好准备。
在美国，龙卷风发生最频繁的地区通常被称为龙卷风走廊（Tornado Alley）：它位于美国的大平原地区，包括德克萨斯州北部、俄克拉荷马州、堪萨斯州、内布拉斯加州和南达科他州东部。但是，龙卷风可以在包括且不限于以上的地方发展起来，无论是冷爽干燥的空气，还是温暖湿润的空气。超强龙卷风通常发生在美国中西部、南部和大西洋中部地区。美国西部也有龙卷风出现，但是活动却比美国东半部少得多，加拿大和其他国家的发生频率也不会那么高。但是在荷兰，龙卷风的发生率却很高。
准备
[编辑]尽管龙卷风发展非常迅速，但是它不会毫无预兆的突然袭来。气象学家可以确定龙卷风发展的合适的条件，美国国家气象局为此发布了两种警报（不过这名字非常相似而且容易令人迷惑）：
- Tornado Watch - This indicates that conditions are right for tornadoes, but none has been observed. Monitor conditions and listen for further alerts.
- Tornado Warning - A tornado or funnel cloud (a precursor to a tornado's touching down) has been spotted or is indicated by radar. This is when tornado sirens may begin. Seek shelter immediately. When a powerful tornado is headed for a densely populated area, the NWS issues a Tornado Emergency to stress the severity.
Listen
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Some local areas have tornado sirens and lights, especially in Tornado Alley and other regions where tornadoes are a seasonal occurrence. If you hear what sounds like an air raid siren, this is probably a tornado siren sounding, and you should seek shelter immediately. Many communities periodically test these systems at a set time, such as at exactly noon on a weekday of the first week of each month, so check the time and the skies (tornadoes do not develop in sunny weather) before panicking. (Most communities will skip these tests if the weather is stormy, to avoid causing undue alarm.)
Heavy rain and hail can hide a tornado from view. This is especially likely in the more humid regions of the southern and eastern US. Tornadoes will also be very difficult to see at nighttime, unless backlit by frequent lightning. The roar of a tornado (similar to a freight train or a jet aircraft taking off) may be the only sign that one is approaching.
Watch
[编辑]There are some specific signs that a tornado is developing or likely:
- Debris - If you see a cloud of debris being swept into the air in the distance, that could mark the position of a tornado even if you don't see the funnel cloud.
- Green Clouds - Green clouds are normally seen when there is a large amount of ice in the clouds. This is an indication of hail and could be a warning that a tornado is likely.
- Hail - Hail will sometimes occur. The larger the hail the more likely that there may be a tornado associated with the storm.
- Rotation - If you see rotation in the clouds (not just a swirl of wind near ground level, which is an entirely different phenomenon), that may indicate the presence of a tornado or the possibility of a tornado developing.
Day or night, A loud continuous roar or rumble which doesn't fade in a few seconds like thunder or a train could indicate a tornado.
保持安全
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警告：不要在桥下，尤其是地下通道或天桥下躲避龙卷风！由于桥下漏出的飞屑，人们在这次行动中丧生或者严重受伤。龙卷风在桥下趋向于更强，这表明，对于避开龙卷风来说，桥根本不是个好主意。 |
如果龙卷风来临，请不要把自己当成是一个挥舞着相机的游客。不要试图通过拍摄照片来记录您的大冒险。不要试图取回你的行李。只要立即确保自己安全即可。
返回室内！
[编辑]最安全的地方是为了龙卷风的安全而专门建造的避难所或安全屋。在龙卷风地区，这些地区经常出现在农村家庭和活动房屋公园内或附近。最重要的是不要惊慌。保持冷静，找到可以快速到达的最安全的区域。
House
[编辑]如果您处于室内，请远离窗户（窗户可能会破碎），然后转到最低的楼层。如果有地下室，那么就进入地下室，否则就钻到长凳或桌子等比较低的地方。如果没有地下室，就去中间没有窗户的房间，例如壁橱或浴室。如果在浴室，请躺在浴缸中。蹲下来，如果你有一些垫子，比如床垫，可以保护你不受飞来飞去的碎片的伤害，那就把垫子盖在身上。不要浪费时间，试图打开窗户以防止窗户被打破，这样可以更好地利用时间到达避难所。
Tall building
[编辑]Go to the lowest floor or center of the building away from windows and close to an interior wall. Crouch down and cover your head. Do not get in the elevator; you'll be trapped if the electricity goes out, and there's always a chance that the lift mechanism will give out if the roof is damaged. If you're not too high, use internal stairways to reach the ground floor or basement. Stairwells are probably one of the safer places to seek shelter in such circumstances anyway (i.e. no windows, sturdy construction).
Get out!
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The least safe place to be is inside something the tornado can pick up; you're actually better off outside.
Mobile home
[编辑]If you are in a mobile home and there's a tornado warning, you should seek out the nearest storm shelter or protected building. People morbidly joke that mobile homes and trailers must somehow attract tornadoes because they are so often shown on TV as twister disaster areas; the serious truth is that their vulnerability is why they make for the most sensational news clips. Studies have shown that a mobile home is the worst place you can be during a tornado; the broad sides of the structure are like a sail in the wind, and there's nothing to hold them in place. It may sound counterintuitive, but you should leave the mobile home and get in a ditch, culvert, or drain pipe, low to the ground. If you are staying in a mobile home and trailer park ask management if there is a tornado shelter close by. These may be cellars or sturdy buildings.
Car
[编辑]If you are in your automobile and you see a tornado coming, don't try to out-run it; tornadoes can easily outrun a car driving into a 100-mph headwind. Your safest option is to leave the car and get in a sturdy building. If that is not available, get out of the car and get in a low area such as a culvert, drain pipe or ditch. If you are staying in your car, attempt to drive at right angles to the tornado to get out of its path. If the tornado does not appear to be moving left or right, chances are it is coming straight for you. A car is probably safer than a mobile home (less wind-catching surface to drag it into the air), but it's still safer to get out and hunker down low. The best option is to find a ditch to lie flat in, and cover up.
在龙卷风之后
[编辑]当心尖锐的物体和掉落的电源线。不要站在电源线朝下的水中。远离受损严重的房屋和建筑物，因为那里可能会有倒塌的危险。请勿使用打火机和火柴，因为可能有气体泄漏的危险。保持镇静，等待当地紧急救援人员的指示。