本文报道了美国东北部地区的暴风雪天气,解释了湿雪的形成原因及其对雪球和雪人建造的适宜性,同时简要介绍了雪的密度测量方法。
School is out as heavy, wet snow blankets parts of the Northeast. Though it will be a pain to shovel, it makes for perfect snowballs and the most structurally sound snowmen.
A blizzard that brought more than 15 inches of snow to New York City has shuttered schools and stymied travel across New York State, New Jersey, Connecticut, Rhode Island and Massachusetts.
So what to do with all that snow? Well, when you’re done breaking your back shoveling, experts recommend snowball fights and sledding.
The snowfall hitting the Northeast is heavy and high in moisture, the result of cold Arctic air hitting warmer, moist air from the Atlantic. The storm system stalled over the region, dropping all that moisture—now chilled into white flakes—onto roads, power lines, sidewalks and lawns. While adults may decry the need to shovel the wet, heavy snow, it should be perfect for snowmen and snowballs, says Alicia Wasula, a meteorologist and president of the consulting firm STM Weather in Troy, N.Y.
“I don’t think any of the kids are going to complain,” Wasula says.
Conditions in the region were optimized for dense, heavy snow, with air temperatures hovering around freezing. Colder air usually leads to fluffier snow, Wasula says, while temperatures around 32 degrees Fahrenheit (zero degree Celsius) result in heavier, wetter snow because the crystals melt a bit and clump together as they hit the ground. Accumulation can also depend on the type of flake, which is determined by the temperature within the cloud where the snow forms, Wasula says. Classic six-sided snowflakes, known as dendritic flakes, accumulate best.
Meteorologists quantify snow’s density by its snow-to-liquid ratio, which is essentially how much water there is per inch of snow. On average, snow contains about an inch of water per 10 inches of snow, but that varies a lot from storm to storm, Wasula says. The heaviest snow can have a ratio as low as 3:1 or 4:1, meaning every three to four inches of snow contains an inch of water. Meanwhile the fluffiest snow can have ratio of more than 30:1, meaning it takes 30 inches of powder to add up to an inch of water.
Morning observations on the East Coast, taken before 8 A.M. local time, suggested that the snow-to-liquid ratio of the snow that fell overnight was between 10:1 and 15:1 (that ratio could change throughout the day on Monday). That’s not ideal for skiers, who prefer snow with around a 20:1 ratio for a light, floaty ride. But the snow is wet enough to pack nicely into snowballs, build the most structurally sound snowmen and provide a nice, slick surface for sledders. Winds that are associated with the low-pressure system of the storm may keep kids indoors for much of today, but temperatures in the 30s F (low single digits C) in the next couple of days in much of the Northeast will mean more opportunities for kids to play in the white stuff.
“It should stick around for a bit, for sure,” Wasula says.