gently coursing through a solitary existence,

輕輕地流淌在一個孤獨的存在中。

but slowly, their gentility turns to rage.

但慢慢地，他們的溫文爾雅變成了暴怒。

They grow larger and larger, hurling and twisting,

它們越長越大，投擲和扭曲。

and desperately reaching down from the sky,

並拼命地從天上往下伸。

and what began as an invisible shade

和開始時看不見的陰暗面

is turned into a monster.

被變成了一個怪物。

(foreboding music)

(預感的音樂)

Tornadoes are powerful spinning columns of air

龍捲風是強大的旋轉空氣柱

that stretch from the ground to the clouds.

從地面延伸到雲端。

Most are relatively weak,

大多數是相對較弱的。

but the few that grow into large events

但少數發展成大型活動的

are extremely violent and cause immense destruction.

是極其暴力的，造成巨大的破壞。

Tornadoes occur on six of the seven continents.

龍捲風發生在七大洲中的六大洲。

The country with the most tornadoes based on land size

根據土地面積，擁有最多龍捲風的國家

is the United Kingdom with an average of about

是英國，平均約為

33 tornadoes reported each year.

每年報告的龍捲風有33次。

But the country with the greatest overall

但是，總體上最多的國家

number of tornadoes and the most intense

龍捲風的數量和最強烈的

is the United States with over 1,000 reported annually.

是美國，每年有超過1,000份報告。

Tornadoes, no matter where they occur,

龍捲風，無論發生在哪裡。

are classified as either supercell tornadoes,

被歸類為超級龍捲風。

which form within supercells,

這是在超級包裹中形成的。

the most powerful class of thunderstorms,

是最強大的一類雷暴。

or non-supercell tornadoes,

或非超級龍捲風。

which are smaller and weaker

其中較小和較弱的

and form within non-supercell storms.

並在非超大型風暴中形成。

There are many theories surrounding

有許多理論圍繞著

the formation of tornadoes.

龍捲風的形成。

One key component they share

他們共享的一個關鍵組成部分

is the presence of both high and low pressure air

是指高氣壓和低氣壓的存在

in a given space.

在一個特定的空間裡。

Air particles from the area of high pressure

來自高壓區的空氣顆粒

move toward an area of low pressure,

向一個低壓區移動。

a movement that creates wind.

一個創造風的運動。

Non-supercell tornadoes,

非超大型龍捲風。

such as waterspouts and landspouts,

如水龍捲和山洪爆發。

begin when cool high-pressure air

涼爽的高壓空氣時開始

and warm low-pressure air are present,

和溫暖的低壓空氣存在。

particularly near ground level.

特別是靠近地面的地方。

As air particles move horizontally

當空氣顆粒在水準方向移動時

from the high pressure area to the low pressure area,

從高壓區到低壓區。

wind begins to pick up.

開始起風了。

Winds blowing at different speeds

以不同速度吹來的風

and in different directions and altitudes

並在不同的方向和高度上

begin to blow cyclically.

開始循環地吹。

In the case of non-supercell tornadoes,

在非超級細胞龍捲風的情況下。

they turn into an upright spinning vortex.

他們變成了一個直立的旋轉漩渦。

But to create supercell tornadoes,

但要創造超級龍捲風。

the circumstances are slightly different.

情況略有不同。

Violent supercell storms draw warm low-pressure air

猛烈的超級暴風雪吸引了溫暖的低壓空氣

up to a higher altitude,

上升到一個更高的高度。

leaving behind cool high-pressure air near the ground.

留下了靠近地面的涼爽高壓空氣。

Air particles attempting to bring

試圖將空氣粒子

the two levels of air pressure into balance

兩級空氣壓力達到平衡

creates wind that blows vertically.

形成垂直吹動的風。

The wind increases and starts to blow in a cyclical fashion,

風力增大，開始以週期性的方式吹動。

creating a pipe of wind that rolls along the ground.

形成一個沿著地面滾動的風管。

In both cases, an upward current of wind called an updraft

在這兩種情況下，一股向上的風流被稱為上升氣流

provides the final ingredient for creating a tornado.

提供創造龍捲風的最後成分。

In a budding non-supercell tornado,

在一個正在萌芽的非超級龍捲風中。

an updraft stretches its vertical vortex

上升氣流伸展其垂直渦流

until it reaches the clouds.

直到它到達雲端。

To create a supercell tornado,

創造一個超級龍捲風。

an updraft lifts the rolling pipe of wind upward

上升氣流將滾動的風管往上提升

until it stands upright.

直到它豎立起來。

Then it pulls condensation from the skies

然後它從天空中拉出冷凝水

and into the spinning vortex.

並進入旋轉的漩渦中。

As soon as the vortices, supercell or non-supercell,

只要有旋渦，超級細胞或非超級細胞。

connect the ground to the clouds,

連接地面和雲層。

they are officially classified as tornadoes.

它們被正式歸類為龍捲風。

All tornadoes are rated based on a system called

所有的龍捲風都是根據一個叫作

the Enhanced Fujita Scale.

增強型富士達量表。

The Enhanced Fujita, or EF, Scale,

增強型藤田表，或EF表。

classifies tornadoes from a rating of EF0 to EF5.

將龍捲風的等級從EF0到EF5進行分類。

The rating is based on a number of factors,

評級是基於一些因素。

such as the damage a tornado causes

如龍捲風造成的損害

and the Doppler radar estimates of its wind speeds.

以及多普勒雷達對其風速的估計。

EF0 tornadoes are the weakest,

EF0龍捲風是最弱的。

with the wind speeds between 65 to 85 miles per hour.

風速在每小時65至85英里之間。

EF5 tornadoes are the strongest,

EF5龍捲風是最強的。

with the wind speeds exceeding 200 miles per hour.

風速超過每小時200英里。

One of the strongest tornadoes recorded

有記錄的最強龍捲風之一

occurred in Oklahoma City, Oklahoma in 1999.

1999年發生在俄克拉荷馬州的俄克拉荷馬市。

Born from a supercell thunderstorm,

誕生於一場超級大的雷雨。

the EF5 tornado had wind speeds of over 300 miles per hour.

EF5龍捲風的風速超過每小時300英里。

It resulted in 36 fatalities, injured nearly 600,

它導致36人死亡，近600人受傷。

and caused about $1 billion in damages.

並造成約10億美元的損失。

(somber music)

(陰沉的音樂)

(dramatic music)

(戲劇性的音樂)

While tornadoes cannot be prevented,

雖然龍捲風是無法預防的。

measures are being taken to protect communities.

目前正在採取保護社區的措施。

Meteorologists closely monitor storm fronts

氣象學家密切監測風暴鋒面

in high-risk areas and try to forecast

在高風險地區，試圖預測

possible tornadic events.

可能的龍捲風事件。

In doing so, they help mitigate damages to neighborhoods

在這樣做的過程中，他們有助於減輕對社區的損害。

and save countless lives,

並拯救無數的生命。

even in the face of one of nature's most formidable.

即使面對自然界最強大的力量之一。