gravitylover Posted February 17, 2015 Share Posted February 17, 2015 did u guys get any snow up north ? 4" Link to comment Share on other sites More sharing options...
RU848789 Posted February 17, 2015 Share Posted February 17, 2015 Posted this on FB to try to explain ratios to some folks who asked. I know most here are savvier than the average FB poster, but thought some might find it interesting. Here goes... That's what got me going last night. That first half inch looked like it was 95% air - turns out it was even more, as the snow to liquid ratio has been reported as 25:1 by the NWS vs the usual 10:1 (10 inches of snow to 1" of liquid technically means that 10% of typical snow volume is solid and 90% is air; for 25:1, snow:liquid, that would be 4% solid to 96% air, by volume). It was seriously like cotton candy - last night I was speculating it was 20:1, which is almost unheard of around here and 25:1 is nearly unprecedented from what I've read. At 25:1, 0.2" of liquid translates to 5" of snow instead of the usual 2" of snow - since mass is all that matters from a shoveling or driving perspective, that's why the almost 5" we had really seemed like 2" - but was a lot prettier, lol. 25:1 ratios are typical of what they often get in any much colder climate, as the temperature aloft and the temperature of the column both affect snow to liquid ratios. The temp aloft (as well as vertical velocities, as supersaturation levels drive better dendrite growth in the snow growth region) affects whether "classic" dendrite snowflakes are formed or not, as these will layer on top of each other like feathers with lots of air space, as opposed to crystals that are rod or needle-shaped and don't trap as much air between crystals. Lack of wind is also important, as high winds will promote crystal to crystal collisions, breaking the snowflakes and decreasing the snow to liquid ratio. The temp in the column affects whether the falling snow picks up liquid moisture, which can cause falling flakes to "stick together" or agglomerate, packing together more tightly, meaning less air is trapped between crystals on the ground - we had near perfect temps for pretty dendrite formation aloft and the entire column was way below 32F, so no liquid moisture was available to stick to the falling flakes. It's also why I think some of the reported measurements are likely low for some towns. If you didn't measure before 8-9 am, the fluffy snow contracted some. For example, we had 4.5" of snow on the ground when I shoveled/measured around 5:30 am - when I came back out at 8 am to leave for work, about another 1/2" had clearly fallen on my driveway (there was no wind to blow it there), yet I still measured 4.5", since some compaction had already occurred in the deeper snow. As an aside, anyone from the Edison/Metuchen area notice if we had any additional accumulation of snow after 8 am? I left for work and spent almost all of the next 9 hours in a windowless conference room. Thanks. Link to comment Share on other sites More sharing options...
Allsnow Posted February 18, 2015 Share Posted February 18, 2015 Posted this on FB to try to explain ratios to some folks who asked. I know most here are savvier than the average FB poster, but thought some might find it interesting. Here goes... That's what got me going last night. That first half inch looked like it was 95% air - turns out it was even more, as the snow to liquid ratio has been reported as 25:1 by the NWS vs the usual 10:1 (10 inches of snow to 1" of liquid technically means that 10% of typical snow volume is solid and 90% is air; for 25:1, snow:liquid, that would be 4% solid to 96% air, by volume). It was seriously like cotton candy - last night I was speculating it was 20:1, which is almost unheard of around here and 25:1 is nearly unprecedented from what I've read. At 25:1, 0.2" of liquid translates to 5" of snow instead of the usual 2" of snow - since mass is all that matters from a shoveling or driving perspective, that's why the almost 5" we had really seemed like 2" - but was a lot prettier, lol. 25:1 ratios are typical of what they often get in any much colder climate, as the temperature aloft and the temperature of the column both affect snow to liquid ratios. The temp aloft (as well as vertical velocities, as supersaturation levels drive better dendrite growth in the snow growth region) affects whether "classic" dendrite snowflakes are formed or not, as these will layer on top of each other like feathers with lots of air space, as opposed to crystals that are rod or needle-shaped and don't trap as much air between crystals. Lack of wind is also important, as high winds will promote crystal to crystal collisions, breaking the snowflakes and decreasing the snow to liquid ratio. The temp in the column affects whether the falling snow picks up liquid moisture, which can cause falling flakes to "stick together" or agglomerate, packing together more tightly, meaning less air is trapped between crystals on the ground - we had near perfect temps for pretty dendrite formation aloft and the entire column was way below 32F, so no liquid moisture was available to stick to the falling flakes. It's also why I think some of the reported measurements are likely low for some towns. If you didn't measure before 8-9 am, the fluffy snow contracted some. For example, we had 4.5" of snow on the ground when I shoveled/measured around 5:30 am - when I came back out at 8 am to leave for work, about another 1/2" had clearly fallen on my driveway (there was no wind to blow it there), yet I still measured 4.5", since some compaction had already occurred in the deeper snow. As an aside, anyone from the Edison/Metuchen area notice if we had any additional accumulation of snow after 8 am? I left for work and spent almost all of the next 9 hours in a windowless conference room. Thanks. We definitely got 1/2-3/4 of a inch after 8am. We did get a heavier burst of snow around 10am that coated everything up again. What do you have as our seasonal total now 30? The February sun with some salt gets everything down to pavement, by 11am lots where all wet. Very impressed with the ratios...this stuff was like fake snow you see at the mall lol Link to comment Share on other sites More sharing options...
TwcMan Posted February 18, 2015 Share Posted February 18, 2015 Yeah this snow resembled that fake snow you would throw on a dickens christmas village. Link to comment Share on other sites More sharing options...
Allsnow Posted February 18, 2015 Share Posted February 18, 2015 Yeah this snow resembled that fake snow you would throw on a dickens christmas village. Yes! Exactly that. Link to comment Share on other sites More sharing options...
RU848789 Posted February 18, 2015 Share Posted February 18, 2015 We definitely got 1/2-3/4 of a inch after 8am. We did get a heavier burst of snow around 10am that coated everything up again. What do you have as our seasonal total now 30? The February sun with some salt gets everything down to pavement, by 11am lots where all wet. Very impressed with the ratios...this stuff was like fake snow you see at the mall lol With 3.75" Saturday night and if I add the 1/2" to my 4.5" from today, that would be 5.0", which would bring me to 30.5" for the season - that's borderline not kosher, though, if one strictly follows the rules, as one is supposed to measure the maximum accumulated depth in a 24-hr period and I know there was compaction - maybe I should split the difference and go with 4.75". I'm usually a little higher than anyone around me, but I'm certain it's because I always get measurements at the best time, i.e., at the end of an accumulating snow that will compact, like the last two - not a lot of people are out at 2 am or 5 am to measure, lol - or at the exact point of changeover to sleet/ZR/rain, like the 2/2 event. Catching the timing perfectly has saved 1/2" or so on several different storms, which adds up to a few inches, overall. Link to comment Share on other sites More sharing options...
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