|
Post by zoomthundersnow on Jan 9, 2015 14:51:39 GMT -5
No 931 group transmitted here, the NWS calls our office for snowfall, no problem.
|
|
|
Post by weatheri on Sept 17, 2016 16:19:18 GMT -5
I would like to readdress the 931 group. www.nws.noaa.gov/om/coop/reference/Snow_Measurement_Guidelines.pdfThe NWS has clarified the instructions: The following procedures should be followed for observers required to take observations every 6 hours. This is often the case for observers at major airport locations. If you take your observations at this frequency, make sure that you clear your SMB no more frequently than every 6 hours. Record the frequency of observation during the 24-hour period in the comments section of your report. Sum the 6-hour observations to obtain the daily snowfall measurement and report that total at the normal observation time. Never add more than four 6-hourly observations to determine your 24-hour snowfall total. If you add more than four observations it could inaccurately inflate the snowfall total. Because it is not possible for most observers to take snowfall measurements every hour, this standard practice of providing 6 hours between snowfall measurements during a snow event ensures a standard length of time for snow to settle between measurements and helps ensure consistency and uniformity among stations. Note however that if snowfall stops before the end of a 6-hour period that you should measure the total as the greatest amount, even if it occurs before the end of the 6-hour period. If we are to use the 6 hour standard, then why is there a note to use the highest amount even if it stops before the 6 hour period. So now I have a great big HUH? You just finished stating that it is to be measured at the 6 hourly so it can “settle” and we have a standard. Scenerio: It has not snowed in 24 hours and the current snow depth is zero. It starts, then stops after 3 hours. I measure it 2.1”. It melts and then it starts again. At the six hourly, I measure 1.0. Am I to understand the 931sss is the maximum I measured when it stopped, 931021? The guidance seems clear; I clear the board every 6 hours but measure snow when it stops and at the 6 hourly observation. Whichever is greater becomes the amount I use in the 931 group. Snow depth is measured differently. It is the depth at the 6 hourly observation. In the above example, 931025 4/001 would be correct. Am I reading this correctly?
|
|
|
Post by hlsto2 on Sept 18, 2016 7:29:15 GMT -5
nws training guide explains it pretty well. in your case the 931 group would be 93131. as you are measuring the max depth of all new snowfall. another example...3.5" falls and melts down to 2.0". you then receive another 1.0" of new snow in the same six hour period. 93145
|
|
|
Post by hlsto2 on Sept 18, 2016 7:38:17 GMT -5
quote from page 8-8 nws training guide in sfc wx obs:
a. during the six hour period it snows two times. the first snowfall accumulates 3.7 inches of new snow. before the second snow, 3.5 inches of the new snow melts. the second snow adds another 0.8 inches of new snow. the depth of the new snow would be coded 931045
...so the 4/nnn group would be 4/001...provided no additional melting took place before the six hourly. and if NO melting or settling had occurred the group would be 4/005
|
|
|
Post by weatheri on Sept 19, 2016 9:47:29 GMT -5
I get that it is the total of all events. That is the way it has always been done.
However, it is my understanding, following the NWS instructions, we only measure snow when the event ends, and at the 6 hourly observations. If that is the case, you have no idea how much is melting or how much is falling until that measurement. The snowboards are cleared after the 6 hourly measurement so you can start the next snowfall amount.
I also know that snow depth is very different than the 931 snowfall amount.
Scenario: It stops snowing at 1945Z and you measure 1.1" on the board. The board is not cleared since it is not a 6 hourly. At 2210Z, it starts snowing again. At the 6 hourly you measure 0.6.
My point is that since you only measured when it stopped and on the six hourly, you have no idea what transpired in between. Did it all melt or only some of it? What is the new accumulation since it ended? The instructions state to use the higher value for the snowfall, which would be 1.1.
When we measured snow, we took hourly measurements for snow increasing rapidly remark, at the end of the event and for the 6 hourly observation.
|
|
|
Post by skobie on Sept 19, 2016 11:02:30 GMT -5
We haven't done the 931 group for years. Didn't you guys get the memo??? Seriously, our contractor at the time said to stop doing it because it wasn't in the FAA SOW. My interpretation of it was that the NWS hadn't negotiated with the FAA to have the CWOs include 931-group in their obs (amongst other things) when they relinquished control of the CWO program.
skobie
|
|
|
Post by TCU 2U2 on Sept 19, 2016 12:03:02 GMT -5
We haven't done the 931 group for years. Didn't you guys get the memo??? Seriously, our contractor at the time said to stop doing it because it wasn't in the FAA SOW. My interpretation of it was that the NWS hadn't negotiated with the FAA to have the CWOs include 931-group in their obs (amongst other things) when they relinquished control of the CWO program. skobie We were permitted to work up a FLSA, and have been providing the 931sss groups since 2013.
|
|
|
Post by alstein on Sept 19, 2016 14:45:08 GMT -5
Here we don't transmit the 931 group but provide 931 to our local NWS office upon request.
|
|
|
Post by toofarnorth on Sept 19, 2016 17:09:36 GMT -5
We haven't done the 931 group for years. Didn't you guys get the memo??? Seriously, our contractor at the time said to stop doing it because it wasn't in the FAA SOW. My interpretation of it was that the NWS hadn't negotiated with the FAA to have the CWOs include 931-group in their obs (amongst other things) when they relinquished control of the CWO program. skobie We were permitted to work up a FLSA, and have been providing the 931sss groups since 2013. Watch out - Clueless Joe is watching. We turned in 931nnn as part of our FLSA and got chewed for it, even though it cost the FAA nothing. We're still reporting it.
|
|
|
Post by hlsto2 on Sept 20, 2016 10:06:45 GMT -5
nws training guide says the 931nn group is not to be entered into a metar...so...those stations required to report snow depth...according to the FAA contract...have to use late 1800's technology and phone it in. I have seen sites that enter the group in a metar...which makes common sense to do. I guess you could e-mail it in to the local NWS. our latest FAA contract specifies all the snow reporting sites. I guess the sites not on the list who have agreed to help the NWS...who refuses to help us in our fight to keep jobs. I am surprised that the FAA went along with having to report the 931 and 933 groups. these chores can take away valuable time when you are busy with real weather. although.. have had an occasional pilot ask for the water equivilant...for flight planning.
|
|