Yeah I'm sure that's true. I'd just like to understand how they're calculating SLP, that's all.
Looking at your post you used the current temperature (-5 deg C). The weather service SLP calculation uses the mean temperature over the last 12 hrs. That could account for the discrepancy.
My main question is why are you calibrating to SLP? I thought CWOP stations were supposed to report altimeter not SLP.
Here is a link to a CWOP manual that may be useful.
My main question is why are you calibrating to SLP? I thought CWOP stations were supposed to report altimeter not SLP.
Here is a link to a CWOP manual that may be useful.
I looked more carefully at the MADIS QC page for my station. Here is what it says:
Please ensure your station's sensors are working properly and that your sensors are correctly calibrated!
Specifically, double check your barometer calibration (both absolute and relative) and make certain it's correct
We use your absolute barometer reading with your station elevation to determine altimeter pressure value sent to CWOP!
The way I read that, it doesn't say that my station should report Altimeter for relative pressure. It says that it uses my station's reported ABS pressure and converts it to altimeter and then sends it to CWOP. They also link to a video that shows you how to calibrate your ABS and REL pressure on an Ambient 2902B PWS. Basically, the procedure is:
1. Get your location and *console* elevation as accurately as possible.
2. Determine your offset between SLP and ABS using the Keisan Atmospheric Pressure from Altitude Calculator at
https://keisan.casio.com/exec/system/1224579725 (NOT the T and P at dest calculator)
3. Set your REL pressure using the calculated offset.
4. Then get a current local METAR and use the calculated offset to determine your true ABS pressure and set your ABS to that value. That will also adjust your REL pressure since the unit remembers the offset (this I gather, kind of reading between the lines).
Now in the last step it isn't clear whether you're supposed to get the SLP or the altimeter setting from the METAR, but the offset you get from the keisan calculator is clearly between absolute and SLP, so using altimeter wouldn't make sense to me.
But the offset is a little different* than you get with the T and P at destination calculator, because now you are using 15 C at station elevation instead of at sea level. So I wonder which is actually correct.
*In my case, 29.52 vs. 29.68 hPa.