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Post by kukblue1 on Dec 29, 2014 16:31:04 GMT -5
So we had a little bit of snow this weekend. NWS called today wanting to know why we didn't do 931 group? Is 931 group required? Is it in the contract anywhere? Is anyone reporting it? I know it's not in the 7900.5c Kind of funny how NWS wants snow melt, cor samples, and now 931 groups but want nothing to do with the program at all.
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Post by toofarnorth on Dec 29, 2014 19:35:58 GMT -5
Watch out for FAA politics... NWS has called us anytime there has been more than a trace of snowfall... for the last 18 years. 931nnn is in WSOH7, not 7900.5. I'm seeking permission from FAA to do 931 at our site - it is not in our contract.
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Post by toofarnorth on Dec 29, 2014 19:37:27 GMT -5
I should add that we measure snowfall - and have been for at least the 62 years that this site has been open - 931nnn makes sense.
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Post by kukblue1 on Dec 29, 2014 20:38:30 GMT -5
It just seems like since it's not in the contract they don't want it. Now this year they want it. I remember 3 winters ago one month we were told to put it in then the next month not too then the next month put it in. Just make up my mind.
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Post by hlsto2 on Dec 30, 2014 2:33:05 GMT -5
NWS training manual says 931 is not xmtd in a metar...but sent as a supplemental report. but that info is very old. I think if you are a required snow reporting site...then the 931 should be sent in a metar. I see some sites do it...some don't. it's the easiest way to get the info ouit.
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Post by TCU 2U2 on Dec 30, 2014 7:00:09 GMT -5
We have a Facility Level Service Agreement (FLSA) between our site, FAA & NWS to carry the 931sss group.
This is one reason why the FLSA was put into this contract ... to provide services above and beyond the contract's statement of work & JO 7900.5.
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Post by kukblue1 on Jan 4, 2015 14:52:09 GMT -5
So is the 931 group reported to tenth of an inch or is it if you have a trace it's 931000. If I remember correctly a trace would be 931000 but they are trying to tell me otherwise. Of course we have nothing at the station about the 931 group.  |
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Post by TCU 2U2 on Jan 5, 2015 7:39:14 GMT -5
931sss group is reported to 10th of an inch ... and yes, a trace is also reported.
3.7 inches of snow in the past 6 hours reported as 931037
8.0 inches of snow in the past 6 hours reported as 931080
Trace of snow in the past 6 hours reported as 931000
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Post by kukblue1 on Jan 5, 2015 18:13:00 GMT -5
any place I can find this information Online?
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Post by TCU 2U2 on Jan 5, 2015 19:08:09 GMT -5
Says in part ... 3.3.6.2 Depth of New Snow, 931sss (Snowfall). Report the depth of new snow (snowfall) every six hours at 0000, 0600, 1200, and 1800 UTC, when any amount of snow has fallen in the past six hours. The “931” is the code group indicator for depth of new snow. The code letters “sss” represent the depth of new snow (i.e., snow, snow pellets, snow grains, ice pellets, ice crystals, hail) in the past six hours reported in tens, units, and tenths of inches, using three digits. The amount reported for “sss” is the actual amount that has fallen, even if some (or all) of it melted. Trace amounts are coded 931000. Do not code the group if it consists entirely of hail. Two examples follow: a. During the 6-hour period it snows two times. After the first snow there are 2.3 inches of new snow. Before the second snow, 0.5 inches of the new snow melts. The second snow adds another 1.4 inches of new snow. The group “931sss” would be coded 931037. b. During the 6-hour period it snows only one time, but it is of long duration and adds 6.3 inches of new snow. Between melting and drifting, there are only 4.7 inches left by the time of the observation. The group “931sss” would be coded 931063. Full manual is found here (and the above is found on page A-19) ... www.nws.noaa.gov/directives/010/archive/pd01013011a.pdf |
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Post by weatheri on Jan 6, 2015 13:33:20 GMT -5
First, we do not measure snow since there is no grass anywhere to be found within 1/2 mile.
Here are my question.
If it starts snowing at 1200Z, and 0.2 inches of new snow falls before it changes to rain by and by 14Z it has all melted.
Then it mixes with the rain and 0.1 is on the ground by 15Z.
You guessed it, that melts by 16Z.
Then it goes to all snow and when it ends at 1730Z there is 0.3 inches on the ground.
What is the 931 group?
I believe it is 931006 for the 18Z obs with no 4 group and no 933 group.
Next scenario,
The temperature is 38F.
It snowed from 12z to 18Z and the ASOS is reporting a water equivalent of .06.
All the snow has melted shortly after contact with the surface, never making it to a snow depth of 0.1
Do you report a 931 group of 931000?
Since it is "Depth of new snow", I think it is reported as a trace since there never was any measurable accumulation.
The confusing part; the regulation states that the 931 is snow depth not snowfall, and at the end it states, "The
amount reported for “sss” is the actual amount that has fallen, even if some (or all) of it melted."
I'm just curious.
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Post by hlsto2 on Jan 6, 2015 19:59:46 GMT -5
931 is the depth of new snow in the past 6 hours. snowfall and snow depth could be the same if none of the snow melts. 3 inches falls...3 more inches fall and at the 6hr time none has melted and the total depth is 6 inches...931060. 4/006. if 3 inches falls in a six hour period and two inches melt...then another 3 inches falls but due to melting only 2 inches is on the ground at 6 hrly time then: 931060 4/002 both examples for simplicity assume no snow on the ground at the beginning of the 6 hr period.
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Post by skobie on Jan 8, 2015 10:47:01 GMT -5
931 group is not required under the FAA contracts and we have been even told specifically not to put it in by the last several contractors. If you have it in your FLSA, then put it in. Otherwise, only requirements are 4 group and 933 group as far as precip goes.
skobie
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Post by hlsto2 on Jan 9, 2015 12:12:26 GMT -5
I wonder how the NWS determines the snowfall for a site if the 931 is not a requirement. the 933 group has always been a pain. many times it takes away from more critical duties, especially if you have ongoing wx at the time.
7900 page 167 G.3. I knew I had seen this paragraph somewhere. if you area listed site in G.4 that require snow depth measuements...then you are required to do 6 hour snowfall measurements. instead of the 931 group the info is required to be entered in col 34 of MF1M-10C. that seems old school and even more paperwork. it would be easier to xmit the 931 group as needed.
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Post by weatheri on Jan 9, 2015 14:32:44 GMT -5
They teach people how to measure snow and they have those "spotters".
Between that and radar, they come close.
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