Author Topic: "Trace" of snow?  (Read 2925 times)

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Offline miraculon

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"Trace" of snow?
« on: November 01, 2014, 10:34:57 AM »
I know that rain (liquid precip) < 0.01" is reported as a Trace (T).
It is not clear to me from the CoCoRaHS site if this also applies to snow.
Specifically, there were snow flurries that did not visibly accumulate on the snow board or ground.
I did catch the melted liquid in the gauge and reported that.
What do I do with the knowledge that there was snow, but could not be measured? Does "Trace" apply to the snow depth measurement too?

Greg H.



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Offline floodcaster

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Re: "Trace" of snow?
« Reply #1 on: November 01, 2014, 11:11:21 AM »
Yes, it does. If you see one flake during the preceding afternoon and yet nothing on your snowboard the following morning at ob time, report a T for trace of new snow in the last 24 hrs. Your total snow *depth* however would remain zero.
Bill


Offline PaulMy

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Re: "Trace" of snow?
« Reply #2 on: November 01, 2014, 11:15:46 AM »
That is how I reported last winter i.e. T for trace of new snow and T for precipitation equivalent.
 
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Offline miraculon

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Re: "Trace" of snow?
« Reply #3 on: November 01, 2014, 01:42:14 PM »
Thanks, I went in and edited today's report with the "T" for new snow....

Greg H.


Blitzortung Stations #706 and #1682
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Offline PaulMy

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Re: "Trace" of snow?
« Reply #4 on: November 01, 2014, 02:15:15 PM »
Quote
If you see one flake during the preceding afternoon
I actually hadn't used this precise fact in my reporting last winter :|   
 
We do get a lot of days that has some snow flakes flying about but no ways near an amount that would accumulate to seeing anything on the ground.  I have however reported Trace a number of times where there was some coverage on the ground even if it was only a small fraction of a cm.
 
Paul

Offline Cutty Sark Sailor

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Re: "Trace" of snow?
« Reply #5 on: November 01, 2014, 03:33:16 PM »
If you have a "T".. that is, if you saw a flake, report as "T" in new snow, just as you would for a single raindrop under 'precipitation' (unmeasurable).  If you don't take a "core Sample"... and melt it.. leave it as NA....assuming you had no accumulation, or report "0" meaning there was "no snow to measure' (which isn't exactly correct, but CCR knows what you meant).  I mean, if there's nothing to 'core'.. there's Zero... for "depth of snow".. if no snow cover it theoretically should be "0" for snow depth, and no 'meltable' water available for 'runoff'... any "T" of snow which sublimed or melted, whatever would be in your "Total Precip" entry... as it would typically 'fall' into the cylinder for total Precip. You then use the 'comments' to explain... Please use the comments!  They are extremely valuable to those who use CCR data! And if there's something you need 'help' or advice about, or if you're questioning your own report, ask it in "Comments" and hopefully someone will get back to you!
 


Offline PaulMy

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Re: "Trace" of snow?
« Reply #6 on: November 01, 2014, 04:47:58 PM »
Actually the Training Slide Show on CoCoRaHS doesn't mention Trace of new snowfall at all - it only says "Report your measurements of new snowfall to the nearest tenth of an inch".  Then the equivalent precipitation of that is entered as well and it mentions "Trace".
 
However, in snow on the ground it says "If half the ground has 2.0" and half the ground is bare, report 1.0" as your total depth.  If more than half the ground is bare report "T" (Trace) and mention the range of depth in your comments."
 
Looks like I was doing it wrong for new snowfall by using Trace #-o but had been entering the equivalent precipitation correctly as Trace =D&gt; .

But for very light rain it says: "We call this a "trace" of rain. This should be reported as "T" on your reports. Even if there were just a few drops that don't even dampen the gauge, you should still report a trace."  and looks like I have been doing this wrong - but I hadn't thought I needed to stay up all day and all night to check on any "few drops".
 
Paul

Offline C5250

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Re: "Trace" of snow?
« Reply #7 on: November 06, 2014, 11:36:52 PM »
"Trace" is anything less than 0.1" of accumulation.

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Offline ValentineWeather

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Re: "Trace" of snow?
« Reply #8 on: November 07, 2014, 12:26:59 AM »
The way I understand it the only place you use trace is in Rain and Melted Snow to the nearest hundredth inch. A few observed snowflakes or moisture on/or inside gauge but under .001 would be a trace and qualify. NA value is for unknown.

New Snowfall section:
Accumulation of new snow in inches to the nearest tenth would be 0 because they are asking for nearest tenth.
Melted value from core to the nearest hundredth would be 0 because they are asking for nearest hundredth.   

Total Snow and Ice on Ground at Observation Time:
Depth of total snow and ice (new and old) in inches to the nearest half inch and if less than 1/2, it would be 0.
Melted value from core to the nearest hundredth if less than 1 hundredth it would also be 0.
 
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Offline Cutty Sark Sailor

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Re: "Trace" of snow?
« Reply #9 on: November 07, 2014, 06:04:46 AM »
Snow and Ice (Graupel, e.g.) is tough... CCR wants to know  "Did it snow? How Much? Is there any on the ground?  How Much?"  etc....  Now, the 'caveat' here is this:  We're all volunteers... we don't do a thing to endanger our life or limb... and we report as best we can.... Having said that, let me suggest the following:
The way I understand it the only place you use trace is in Rain and Melted Snow to the nearest hundredth inch. A few observed snowflakes or moisture on/or inside gauge but under .001 would be a trace and qualify. NA value is for unknown.
Best way is never use NA in this block. Report what you see, what's in the gauge: Zero, T or some value. Use NA only if you didn't take a 'gauge' measurement.  NA virtually mandates a 'multiple day report'... "some snow, rain, ice today but I made No Attempt to measure it"... next day's report would be in error, technically you should submit a 'multiple day" instead of "today's" Precip.  Follow me? Many of us will use a zero here, and for total snow, even throughout the summer... indicating "No frozen Precip."
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New Snowfall section:
Accumulation of new snow in inches to the nearest tenth would be 0 because they are asking for nearest tenth.
Melted value from core to the nearest hundredth would be 0 because they are asking for nearest hundredth.   
Accumulation: NA (No Attempt) tells them nothing. 0 says it didn't snow. T says 'one or more snowflakes fell, but I've less then a tenth inch"  T (or even zero, depending on what you add in "comments") here also means "It snowed, but melted before I could measure it.. total liquid is included above"....
Core: NA or actual value, which can be zero, or T. If you don't core you use NA, or even T if there's just a 'trace' of accumulation, whether you cored or not... there's still 'snow' on the ground that will melt someday,... If you have no snow accumulation at all, use zero. If depth varies across your location, You might, e.g., take 3+ measurements and report 'average' depth here. Your core value is 'some percentage' (average) of whatever group of measurements you 'melted'.. so to speak...
Quote
Total Snow and Ice on Ground at Observation Time:
Depth of total snow and ice (new and old) in inches to the nearest half inch and if less than 1/2, it would be 0.
Melted value from core to the nearest hundredth if less than 1 hundredth it would also be 0.
CCR would, ideally, like to have these figures at least weekly, mostly in the more 'snow prone" areas.. The amout of 'water' runoff availability is important. And Snow cover has that.   Many of us report the 'totals' daily.... and that's the best way, in truth.  Others report that total every few days. If not 'measuring'.. then you use NA,.... but if it's obvious you have less than 0.5"  I'd suggest keep using "T" for the duration... which indicates "Snow Cover Present, but thin"... if you will,...
Depth would be T if < 0.5"   not zero. Zero is 'no total snow"   or "NA.. didn't measure (No Attempt)"
If you have 1" on 'half the ground surface" and bare ground on the other half... then your total snow on ground would be 0.5"... average, right?  and your core sample would be " melted core times 50%" ... assuming one sample from the '1 inch' area.

FINALLY... use the 'comments' section to explain...
here's the deal... as a comment reader for CCR... we see mention of "snow", but "NA".  We then 'flag' the report for further follow up by Coordinators, or QC.  If a station 2 miles from you reports something totally different, you get flagged.. in all likely hood... so use the comments!   Explain what you see, how you did it, etc... this enables CCR QC, or you local coordinators, the NWS, other data users, to evaluate and give you feedback if necessary!  You can also ask questions about such things, as this thread, in the "Comments" and we should catch it, and refer it to the appropriate CCR staff.  In Comments, tell us you saw 'wild turkeys'... first robin... you're going on vacation for a few days (then we'll watch for a "Multiple day report" when you return)  Tell us you had 'hail' and submitted a hail report.. Tell us you submitted a "significant" report, eg....   The comments are very important... very.
« Last Edit: November 07, 2014, 06:47:13 AM by Cutty Sark Sailor »
 


Offline ValentineWeather

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Re: "Trace" of snow?
« Reply #10 on: November 07, 2014, 06:27:52 AM »
Good explanation Cutty. This is something not covered very well.
Randy

Offline Cutty Sark Sailor

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Re: "Trace" of snow?
« Reply #11 on: November 07, 2014, 06:43:12 AM »
Good explanation Cutty. This is something not covered very well.
Yeah, It's a very problematic topic.... frozen Precip is a big bear, and difficult... especially in areas prone to a 'mixed' type Precip.  My response above is based on experience, as well as the training... and from countless monitoring of CCR.... here's the thing... as an observer, you do the best you can. You do it the way you understand it. You do it with the number one priority being your safety and convenience.... all CCR asks is you note your methods and experience for that particular observation in the 'comments' section.  I know for a fact that a couple of paradigms have changed because of observers comments!  Use 'em!  er... careful of weird abbreviations and acronyms... remember many observers who watch the comments, etc, don't have a clue about "DP", "SlHg", "ALT", etc...so try to "devolve" back to layman's lingo...
 


Offline miraculon

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Re: "Trace" of snow?
« Reply #12 on: November 07, 2014, 11:31:37 AM »
I asked my CoCoRaHS Regional Coordinator at the NWS office in Gaylord, MI.

Quote
I tried to hunt around the CoCoRaHS site and view the training material on snow measurents and it is not clear to me on how to report the situation where snow occurred but did not accumulate appreciably on the ground. For example, on Halloween day we saw a fairly significant flurry but it did not stick to the grass or "accumulate". My thought was to record it as a T (trace) for the snow fall. The liquid did accumulate in the gauge and I reported that measurement. The web form did accept the "T" for the snow.

Here is the response that he gave me regarding the "trace of snow" issue:

Quote
Hey Greg:

You are exactly correct with your analysis. If it snowed but didn't accumulate, you will always record a trace, despite the fact that sometimes you may even have appreciable liquid precipitation. For example, two nights ago at my station, it snowed for 2 hours but never really accumulated. I had over 0.12" of liquid, but only a trace of snow since there was nothing on my snowboard.

Hope this clears things up, and please feel free to post this answer.

-Dave

Greg H.



Blitzortung Stations #706 and #1682
CoCoRaHS: MI-PI-1
CWOP: CW4114 and KE8DAF-13
WU: KMIROGER7
Amateur Radio Callsign: KE8DAF