为什么准确预测降雪如此困难

为什么准确预测降雪如此困难

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.

谈论小雪或轻尘是一回事。 但是，当您当地的气象学家开始提及严重降雪或您的天气应用程序中突出显示雪花图标时，可能会造成破坏。

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).

国家冰雪数据中心(NSIDC)表示，降雪预报比以往任何时候都更加准确，但对气象学家来说仍然具有挑战性。

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.

有很多条件需要考虑:如果会下雪，会下多少雪，会在哪里下雪。所有这些因素反过来又受到其他问题的影响。

Snowfall can vary in close distances

降雪在很近的距离内会发生变化

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.

雪不是到处均匀地落。你可能还记得冬季风暴，一个社区被大雪覆盖，而几英里外的另一个社区几乎没有雪花。

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.

据NSIDC称，在大雪期间，有时最大的降雪会出现在非常窄的地带。而且这种情况只会发生在很小的范围内，以至于预测工具无法预测。

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.

据气象频道报道，这些波段可能只有5到10英里宽。它们每小时的降雪率超过1英寸，而几英里外的地区降雪率更低，甚至没有降雪。

Temperature matters

温度很重要

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.

下雪时的寒冷程度也会影响到地上的雪量，甚至是雪的类型。

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.

如果雪落的时候温度相对较高，那么当它落到地面时就会融化，变成路上和人行道上的雪泥，而且不会积累。然后，当夜间气温再次下降时，那些泥浆和湿气就会变成冰。如果天气够冷，雪就会越积越多。

Forecasts change

预测变化

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.

气象学家无法提前几天准确地预测降雪。所以，当你看到或听到10天的天气预报时，不要轻信。

"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.

气象频道的资深气象学家乔纳森·埃尔德曼说:“即使我们距离开始发布具体降雪预报的时间已经很近了，仍然有相当多的问号。”

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.

埃尔德曼说，正常情况下，降雪会落在低压中心的北部和西北部。如果轨道改变了，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.

早期的预测可能基于一千多英里以外的一个系统。当它越来越近的时候，它可能会随着雪的变化而变化，也可能不会。

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.

再加上湿度、温度、风和其他可能影响冬季降水的因素的变化，以及用于确定预报的技术的限制。

"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."

美国国家气象局负责火灾和公共天气服务的伊莱·杰克告诉Live Science:“大气非常随机，有很多东西相互作用——水、大气结构、陆地摩擦。”“对我来说，能拍下这样的照片真是太不可思议了。”