Snowfall Ratios

[AaronPippin]

I wasn't sure whether to put this into the winter wx section, but I figured since this is more of an educational question I would put it here.

How or where would I go to find snowfall ratios. What I mean, if the storm is progged to dump .5in of liquid, how would I figure out the ratio (10:1, 12:1, 15:1, ect) to determine forecasted snowfall amounts? Is there a computer model that does this automatically, if so where on the internet can I find that output. Or is it something I would have to look at Skew-T's and determine myself mathematically?

Thanks,
Aaron

 

[Andrew Herron]

The Bufkit Warehouse will show you QPF and Snowfall totals, you can even change the ratio and recompute if you so desire:

http://www.meteor.iastate.edu/~ckarsten/bufkit/data/index.html

Click on a TAF site and then click 'Visualize Data'.

 

[AaronPippin]

Thanks Andrew... I actually thought maybe Bufkit did the formulation for me. I already had Bufkit downloaded just never took the time to get to know how to use it. I've watched the tutorials on it, but actually sitting down and playing with if I haven't ever done yet.

Thanks,
Aaron

 

[Andrew Ryan]

I wasn't sure whether to put this into the winter wx section, but I figured since this is more of an educational question I would put it here.

How or where would I go to find snowfall ratios. What I mean, if the storm is progged to dump .5in of liquid, how would I figure out the ratio (10:1, 12:1, 15:1, ect) to determine forecasted snowfall amounts? Is there a computer model that does this automatically, if so where on the internet can I find that output. Or is it something I would have to look at Skew-T's and determine myself mathematically?

Thanks,
Aaron

Snowfall ratios are incredibly hard to predict but they generally are less than 15:1 and usually around 12:1 or 10:1. That's a good rule of thumb. There's a lot that can influence snowfall ratios (high winds, dynamics of the system, etc), so it's hard to get a good grasp on the actual snowfall ratio.

I don't like to use Bufkit since it spits out wild estimates that are 3 to 4 times a realistic amount.

 

[rdale]

Snow ratios depend where you are. 10:1 is primarily down south, Baxter shows most of the "snow belts" in a 12-16:1 region.

If you are using an older version of Bufkit, it may not have the Cobb snow tool integrated. There's no way the Cobb ratios are 3-4x off. It might be a model error or you have a prehistoric BUFKIT running.

http://www.meteor.iastate.edu/~ckarsten/cobb/cobb.php?model=gfs&site=kokc

 

[AaronPippin]

Thanks guys. Typically when looking at QPF I use between a 10:1-12:1 ratio. So yeah I know I am in the ballpark anyway. But I was just wondering if there was a specific model or output algorithm that a model would spit out and give me its idea too.

Thanks for the replies,
Aaron

 

[Patrick Marsh]

Snow ratios depend on atmospheric moisture content, pressure, and temperature during ice-nucleation -- simultaneously. It's a highly non-linear system that is next to near impossible to simulate with today's computers. Typically the colder you are, the higher the snow-to-liquid ratio. For most big snow falls, you want strong lift, high moisture content in the dendritic snow growth region (this gives you the big snow flakes) that is betwen -12C and -18C.

Edit: That should read, "today's computer models"

 

[GPhillips]

A couple modules in Winter Weather AWOC cover some of the basics of snow ratios and snow production
http://www.wdtb.noaa.gov/courses/winterawoc/IC6/lesson5/part1/player.html
http://www.wdtb.noaa.gov/courses/winterawoc/IC6/lesson5/part2/player.html

and links to snow ratio climatology from CIPS at SLU
http://www.eas.slu.edu/CIPS/slr.html
http://www.eas.slu.edu/CIPS/SLR/slrmap.htm