[gradsusr] Confusiong about WEASDSFC, GFS

Tue Sep 29 10:23:36 EDT 2015

Chris and other interested parties--

This has been a difficult nut to crack for both modelers and operational
forecasters. Lots of factors affect snow depth: the vertical temperature
profile as you've been discussing, but also wind (which will tend to
compact the snow), whether or not there's upward motion in the dendritic
growth zone to create those low-density fluffy flakes that can make 20:1
snow depth to WEASD, ground temperatures, and others.  It's an entire topic
of research in operational meteorology.

That being said, I'll have to check out that Kucera link also. :-)

Bill

Dr. William R. Bua
UCAR/COMET/NCEP/EMC
5830 University Research Court #2784
College Park, MD 20740
301-683-3806

On Tue, Sep 29, 2015 at 9:42 AM, Christopher Gilroy <chris.gilroy at gmail.com>
wrote:

> Ahh, yea I just do the programming for a degree'd met. He wanted to base a
> formula around 2m tmp, 700mb temp and 850mb temp. That's an interesting
> link too.
>
>
>
> On Tue, Sep 29, 2015 at 9:21 AM, Stephen McMillan <
> smcmillan at planalytics.com> wrote:
>
>> Chris,
>>
>> I suppose there are a number of vertical-temperature based
>> formulas/algorithms out there, one of which is the Kuchera method which
>> uses an algorithm based, in part, on the max temperature between 500mb and
>> the surface  It seems to work fairly well for most scenarios.   Here's a
>> link for more information:
>> http://www.wxcaster.com/gfssnow.txt
>>
>> Hope that helps--
>> Stephen Mc
>>
>> On Tue, Sep 29, 2015 at 9:11 AM, Christopher Gilroy <
>> chris.gilroy at gmail.com> wrote:
>>
>>> Hey Stephen,
>>>
>>> Thanks for your response I figured that out after the fact. I appreciate
>>> the help you've given me with this the past few days. One last question I
>>> have to throw out there, what would your thoughts be on having a "dynamic"
>>> ratio based on vertical temperatures? Do you think it'd be wildly
>>> inaccurate or? I seen Ryan Maue make a comment one time about it causing
>>> confusing and/or being great for certain areas but terrible for other areas.
>>>
>>> On Tue, Sep 29, 2015 at 9:07 AM, Stephen McMillan <
>>> smcmillan at planalytics.com> wrote:
>>>
>>>> Chris,
>>>>
>>>> If you want to convert amounts in mm to in, you need to divide by 25.4,
>>>> not 2.54 (or, multiply by the 0.03937 you had in your example).    To go
>>>> the other way (in to mm), multiply in. amounts by 25.4.
>>>>
>>>> However, if you are converting mm to in. and using a 10:1 snow-liquid
>>>> ratio, then simply dividing the weasdsfc amounts by 2.54 should achieve the
>>>> same result as dividing by 25.4 (multiplying by 0.03937) then multiplying
>>>> result by 10.  Result would be in inches.
>>>>
>>>> Stephen Mc
>>>>
>>>>
>>>>
>>>> On Tue, Sep 29, 2015 at 8:41 AM, Christopher Gilroy <
>>>> chris.gilroy at gmail.com> wrote:
>>>>
>>>>> Alright, I have two primary questions, and if the answers are yes to
>>>>> both, the follow-up makes no sense to me.
>>>>>
>>>>> 1.) weasdsfc is water equivalent based in mm, correct?
>>>>> 2.) weasdsfc has no "default" liquid:water ratio, correct? A
>>>>> meteorology friend of mine said 'typically' 10:1 is a good standard, so I'm
>>>>> unsure if the model is based around that or not?
>>>>>
>>>>> I'm fairly certain I'm correct on #1. I'm unsure on the other 2
>>>>> though, but here's my current situation. If I use the expression below:
>>>>>
>>>>> 'd
>>>>> const((sum(maskout(weasdsfc-weasdsfc(t-1),weasdsfc-weasdsfc(t-1)),t=2,t='%i%')/2.54),
>>>>> 0, -u)'
>>>>>
>>>>> I get an identical looking map as another well known sites 10:1 snow
>>>>> accum, in inchs. The confusion part of that equation should be converting
>>>>> (/2.54) IN to MM, no?
>>>>>
>>>>> Now, if on the other hand I do the (if I'm understanding this right)
>>>>> "correct" calculation to convert mm to in:
>>>>>
>>>>> 'd const((sum(maskout(weasdsfc-weasdsfc(t-1),weasdsfc-
>>>>> weasdsfc(t-1)),t=2,t='%i%')*0.039370), 0, -u)'
>>>>>
>>>>> I get very, very, very little snow plotted.
>>>>>
>>>>> Now, I am using the sflux files instead of the pgrb2.0p25 files, which
>>>>> I thought the flux files maybe used different units or something but they
>>>>> don't, weasdsfc is still [kg/m^2] which should mean (unless my
>>>>> expression is more of a hack than I would have imagine) I should be getting
>>>>> the opposite outputs of what each expression is actually producing?
>>>>>
>>>>> I don't know if I'm missing a parenthesis group somewhere and I'm
>>>>> somehow getting an inches, 10:1 snow accum plot with my code by "accident"
>>>>> or what? :-/
>>>>>
>>>>> _______________________________________________
>>>>> gradsusr mailing list
>>>>> gradsusr at gradsusr.org
>>>>> http://gradsusr.org/mailman/listinfo/gradsusr
>>>>>
>>>>>
>>>>
>>>> _______________________________________________
>>>> gradsusr mailing list
>>>> gradsusr at gradsusr.org
>>>> http://gradsusr.org/mailman/listinfo/gradsusr
>>>>
>>>>
>>>
>>>
>>> --
>>> -Chris A. Gilroy
>>>
>>> _______________________________________________
>>> gradsusr mailing list
>>> gradsusr at gradsusr.org
>>> http://gradsusr.org/mailman/listinfo/gradsusr
>>>
>>>
>>
>> _______________________________________________
>> gradsusr mailing list
>> gradsusr at gradsusr.org
>> http://gradsusr.org/mailman/listinfo/gradsusr
>>
>>
>
>
> --
> -Chris A. Gilroy
>
> _______________________________________________
> gradsusr mailing list
> gradsusr at gradsusr.org
> http://gradsusr.org/mailman/listinfo/gradsusr
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://gradsusr.org/pipermail/gradsusr/attachments/20150929/4d827f1f/attachment.html 