為什么準(zhǔn)確預(yù)測降雪如此困難

為什么準(zhǔn)確預(yù)測降雪如此困難

It's one thing when there's talk of flurries or a light dusting. But when your local meteorologist starts mentioning serious snowfall or the snowflake icon is prominent on your weather app, it can cause havoc.

談?wù)撔⊙┗蜉p塵是一回事。 但是，當(dāng)您當(dāng)?shù)氐臍庀髮W(xué)家開始提及嚴(yán)重降雪或您的天氣應(yīng)用程序中突出顯示雪花圖標(biāo)時，可能會造成破壞。

The forecast says wintry wonderland, but that may not be what you get. (Photo: Lipatova Maryna/Shutterstock)

Snow forecasts are more accurate than ever, but they're still challenging for meteorologists, says the National Snow and Ice Data Center (NSIDC).

國家冰雪數(shù)據(jù)中心(NSIDC)表示，降雪預(yù)報比以往任何時候都更加準(zhǔn)確，但對氣象學(xué)家來說仍然具有挑戰(zhàn)性。

There are so many conditions to take into consideration: If it will snow, how much it will snow and exactly where it will snow. All those factors are, in turn, impacted by other issues.

有很多條件需要考慮:如果會下雪，會下多少雪，會在哪里下雪。所有這些因素反過來又受到其他問題的影響。

Snowfall can vary in close distances

降雪在很近的距離內(nèi)會發(fā)生變化

Sometimes one neighborhood will have snow while another nearby community will just get a dusting. (Photo: marekuliasz/Shutterstock.com)

Snow doesn't fall evenly everywhere. You might remember winter storms where one neighborhood was blanketed while another neighborhood just a few miles away barely got a dusting.

雪不是到處均勻地落。你可能還記得冬季風(fēng)暴，一個社區(qū)被大雪覆蓋，而幾英里外的另一個社區(qū)幾乎沒有雪花。

During intense snows, sometimes the heaviest snowfalls will happen in very narrow bands, according to NSIDC. And it will occur on such a small scale that forecast tools won't see it.

據(jù)NSIDC稱，在大雪期間，有時最大的降雪會出現(xiàn)在非常窄的地帶。而且這種情況只會發(fā)生在很小的范圍內(nèi)，以至于預(yù)測工具無法預(yù)測。

These bands may be as narrow as 5 to 10 miles wide, reports The Weather Channel. They can produce snowfall rates of more than 1 inch per hour, while an area just a few miles away gets much less, or even no snow.

據(jù)氣象頻道報道，這些波段可能只有5到10英里寬。它們每小時的降雪率超過1英寸，而幾英里外的地區(qū)降雪率更低，甚至沒有降雪。

Temperature matters

溫度很重要

A slight difference in temperature can mean the difference between snow and slush on the streets. (Photo: lazyllama/Shutterstock.com)

How cold it is during a snowfall also affects how much snow — and even the type of snow — that ends up on the ground.

下雪時的寒冷程度也會影響到地上的雪量，甚至是雪的類型。

If it's relatively warm as the snow falls, it could melt by the time it hits the ground, turning to slush on the roads and sidewalks and never accumulating. Then, when temperatures drop again overnight, that slush and wetness will turn to ice. If it's cold enough, the snow will keep piling up as it falls.

如果雪落的時候溫度相對較高，那么當(dāng)它落到地面時就會融化，變成路上和人行道上的雪泥，而且不會積累。然后，當(dāng)夜間氣溫再次下降時，那些泥漿和濕氣就會變成冰。如果天氣夠冷，雪就會越積越多。

Forecasts change

預(yù)測變化

Forecasts are usually only accurate a few days in advance. (Photo: ninefotostudio/Shutterstock)

Meteorologists can't predict snowfall with much accuracy more than a few days ahead of time. So when you see or hear a 10-day forecast, take it with a huge grain of salt.

氣象學(xué)家無法提前幾天準(zhǔn)確地預(yù)測降雪。所以，當(dāng)你看到或聽到10天的天氣預(yù)報時，不要輕信。

"Even when we're close enough to begin issuing specific snowfall forecasts, there can be considerable remaining question marks," says the Weather Channel's senior meteorologist Jonathan Erdman.

氣象頻道的資深氣象學(xué)家喬納森·埃爾德曼說:“即使我們距離開始發(fā)布具體降雪預(yù)報的時間已經(jīng)很近了，仍然有相當(dāng)多的問號。”

Normally snow falls to the north and northwest of the track of a low pressure center, Erdman says. If the track changes, so does the chance of snow.

埃爾德曼說，正常情況下，降雪會落在低壓中心的北部和西北部。如果軌道改變了，那么下雪的可能性也就增加了。

Early forecasts may be based on a system more than 1,000 miles away. As it gets closer, it can change along with the snow it may or may not bring with it.

早期的預(yù)測可能基于一千多英里以外的一個系統(tǒng)。當(dāng)它越來越近的時候，它可能會隨著雪的變化而變化，也可能不會。

Add to that changes in moisture and temperature and winds and other elements that can impact wintry precipitation, as well as the limits of technology used to determine forecasts.

再加上濕度、溫度、風(fēng)和其他可能影響冬季降水的因素的變化，以及用于確定預(yù)報的技術(shù)的限制。

"The atmosphere is very random, and there are lots of things that interact — water, the structure of the atmosphere, friction from the land," Eli Jacks, chief of fire and public weather services at the National Weather Service, told Live Science. "To me, it's quite amazing that we can capture it at all."

美國國家氣象局負(fù)責(zé)火災(zāi)和公共天氣服務(wù)的伊萊·杰克告訴Live Science:“大氣非常隨機，有很多東西相互作用——水、大氣結(jié)構(gòu)、陸地摩擦。”“對我來說，能拍下這樣的照片真是太不可思議了。”