THAT UNCERTAIN TIME OF YEAR WHEN WE AWAIT THE NEXT BIG STORM TO SEE WHERE IT WILL MAKE LANDFALL

每年最令人憂心忡忡的時節，不知道下個颶風的登陸時間、地點

AND WHEN EVERYONE REALLY WANTS TO KNOW - WHAT THEY WILL NAME IT.

而大家也都好奇著新颶風的名字

BUT WHILE WE WAIT - LET'S TAKE A MINUTE TO CONSIDER WHY EVEN HAVE A SEASON FOR HURRICANES IN THE FIRST PLACE.

但在等待的同時，我們先花個幾分鐘了解為什麼會有所謂的「颶風季」

SO IN ORDER TO UNDERSTAND WHY WE HAVE A HURRICANE SEASON,

為了更充分了解颶風季的起源

LET'S BUILD A HURRICANE.

我們先來「造個颶風」吧！

THE PERFECT HURRICANE RECIPE CALLS FOR PRECURSOR STORMS, WARM WATERS, AND LOW WIND SHEAR.

要製作一個「完美」的颶風需要：風暴雛形、熱帶地區的溫水以及低風切

LET'S START WITH PRECURSOR STORMS.

先從風暴雛形講起

HURRICANES BUILD FROM SMALLER WHAT ARE CALLED PRECURSOR STORMS,

颶風是由小的風暴雛形所致

START WITH A SMALL DISTURBANCE OR A THUNDERSTORM,

起於天氣擾動或雷暴

ADD WARM WATER AND WIND, WHICH WE'LL GET TO IN A SECOND,

之後加入暖水和風，它們很快找到的新夥伴

TO BUILD THE STORM BIGGER AND BIGGER AND BIGGER UNTIL IT BECOMES A HURRICANE, A.K.A.

短時間內就把颶風越造越大，最後形成了颶風，也就是我們所熟知的

TROPICAL CYCLONE WITH SUSTAINED WINDS OF 74 MILES PER HOUR OR MORE,

熱帶氣旋，每小時風力可達74英里(118公里)以上

WHICH IS BASICALLY LIKE PUTTING YOUR HEAD OUT THE WINDOW ON THE HIGHWAY.

就等同於在高速公路時把頭伸出窗外的感覺

WHOO HOO!

呦呼！

NOW, IN THE ATLANTIC AREA, THESE PRECURSOR STORMS SWEEP IN FROM AFRICA

在大西洋區，這些小風暴橫掃非洲

IN WHAT ARE CALLED EASTERLY OR TROPIC WAVES,

我們稱它為東風波或熱帶波

BASICALLY, BANDS OF THUNDERSTORMS THAT MOVE WEST ACROSS THE TROPICS.

大致由一群雷暴在熱帶區由東向西移動

THESE ARE OUR PRECURSOR STORMS.

這就是我們的風暴雛形

[BELL DINGING] ANOTHER INGREDIENT IN THE HURRICANE RECIPE IS

(鐘響)第二個登場的是

A WARM OCEAN.

溫暖的海水

AS AIR FLOWS OVER THE OCEAN, IT TRANSFERS HEAT AND WATER VAPOR

當氣流在海面上流動時，它會轉換熱量，水就會

UP INTO THE ATMOSPHERE.

蒸發到大氣內

THROUGH A CYCLE OF EVAPORATION AND CONDENSATION, THE WARM, WET

經過蒸發、凝結的循環，溫暖潮濕的

AIR BUILDS CLOUDS AND CREATES UPDRAFTS.

水氣就會形成雲，形成上升氣流

THIS WARM, WET AIR ACTS AS FUEL.

溫暖潮濕的水氣就像是燃料

ADD MORE FUEL TO THE FIRE, SO TO SPEAK, AND YOU BUILD A STRONGER HURRICANE.

而燃料越是充足火就越旺，同樣的道理，越多溫暖潮濕的水氣，所形成的颶風就越強

[BELL DINGING] HURRICANES GAIN STRENGTH BY FORMING HIGH INTO THE ATMOSPHERE.

(鐘響)在上升的過程中，颶風漸漸增強

AND IN ORDER TO FORM HIGH INTO THE ATMOSPHERE,

而為了要繼續向上

THE ATMOSPHERE NEEDS TO BE SOMEWHAT CALM, NOT TOO WINDY UP HIGH, NOT TOO WINDY DOWN LOW.

大氣狀態相對需較穩定，高處、低處的風都不能太強

IF ONE OR THE OTHER CHANGES, THE HURRICANE CAN BASICALLY TOPPLE OVER AND FIZZLE OUT.

如果有任何變動，颶風就會崩解並消失

SO WE NEED LOW WIND SHEAR, WHICH MEANS THERE'S LITTLE DIFFERENCE BETWEEN THE WIND IN THE HIGH VERSUS LOW ATMOSPHERE.

這就是為何我們需要低風切，它代表著，無論在高處或低處，風勁是沒有差別的

OUR HURRICANE STAYS STANDING, AND ITS CIRCULATION IS NOT DISRUPTED BY STRONG WINDS.

我們的颶風目前還算穩定，運轉還未受到強風影響

[BELL DINGING] SO NOW THAT WE KNOW WHAT

(鐘響)現在我們已經知道

HURRICANES ARE MADE OF, LET'S LOOK AT WHY THEY ONLY FORM IN

颶風是如何形成的，接下來我們來看為何它只會在

THE ATLANTIC DURING THE SUMMER TO FALL MONTHS.

夏、秋季月份在大西洋海域形成

AND TO DO THAT, WE HAVE TO LOOK ONCE AGAIN AT OUR BASIC HURRICANE INGREDIENTS.

為了一探究竟，我們先重新複習基本的颱風「製造成分」

[BELL DINGING] REMEMBER THOSE PRECURSOR STORMS BLOWING IN FROM AFRICA?

(鐘響)還記得非洲的雷暴雛形嗎？

WELL, THOSE EASTERLY WAVES FORM AROUND SUMMER AND FALL AND PEAK IN SEPTEMBER,

那些東風波在夏秋兩季形成，並在九月達到高峰

BUT DUE TO FACTORS INVOLVING TEMPERATURES

但由於一些因素牽涉，如溫度

AND SOME OTHER ATMOSPHERE SCIENCE WE WON'T GET INTO RIGHT NOW,

及大氣科學成因，這些我們目前還不會談到

IN OUR WINTER, ALL IS QUIET ON THAT EASTERN FRONT, AND THERE ARE NO REAL DISTURBANCES WAITING IN THE WINGS.

冬季，美國東部未受東風波影響，沒有明顯的大氣擾動

AND WINTER IN THE NORTHERN HEMISPHERE MEANS COOLER OCEAN WATERS.

北半球冬季海水相對低溫

COOL WATERS MEANS NO FUEL, MEANS NO HURRICANES.

低溫海水代表沒有「燃料」可以提供，也代表不會形成颶風

AND FINALLY IN THE WINTER MONTHS, THE JET STREAM, WHICH HAD BEEN FARTHER NORTH DURING SUMMER,

入冬後，原本夏季在高緯度的噴射氣流(或稱高速氣流)

SHIFTS BACK DOWN SOUTH,

逐漸南移

WHERE IT CREATES HIGH WIND SHEAR RIGHT SMACK DAB IN THE PRIME AREA FOR HURRICANE FORMATION.

噴射氣流造成高風切，恰巧是形成颶風的黃金地帶

WITH ALL OF THESE FACTORS IN PLAY, THE WINTER MONTHS OF THE

綜合所有要素，這就是為何冬季月份

ATLANTIC REGION ARE HURRICAN-FREE AND WE SHOULD CONSIDER OURSELVES LUCKY.

大西洋地區得倖免於颶風作祟，我們深感萬幸

IN OTHER AREAS OF THE WORLD WHERE OCEAN WATER IS WARM YEAR-ROUND

在全球其他地區，海水終年高溫

AND WIND SHEAR IS WEAK, TROPICAL CYCLONES CAN

風切也低的區域，熱帶氣旋

OCCUR ALL YEAR LONG, AND THAT BEGS ANOTHER QUESTION.

可能在任何月份形成，而這又衍生出另一個問題了

WITH THE CLIMATE WARMING AND ALL, WILL THE ATLANTIC HURRICANE SEASON EXPAND?

因為全球暖化，受到大西洋颶風影響的時間是否會變長呢？

AND SCIENTISTS HAVE DETERMINED THAT THAT'S A REAL POSSIBILITY.

科學家指出，這個推測的確合理

BUT FOR NOW WE'LL HAVE TO HOLD OUR BREATH UNTIL THE HURRICANE SEASON COMES TO A CLOSE

目前，我們只能屏息以待，直到接近颶風季

AND HOPE THAT THIS YEAR WE DON'T MAKE IT ALL THE WAY TO WANDA OR WALTER OR WHITNEY.

並期盼今年沒有像是「旺達」(颶風名)、「惠特妮」(颶風名)不速之客來訪才好