Welcome to the forum!
I don’t own any Davis equipment and don’t upload to CWOP but here goes anyway. Maybe an existing VP2 owner can help clarify if I’ve got any of the Davis details wrong.
Couple things to check/double check:
- The elevation you have entered in your VP2 console is the elevation above sea level of your barometric sensor ( located in your console).
- CWOP requires you to upload Altimeter to them. Uploading SLP instead of Altimeter could be the reason why MADIS is generating errors and complaining about temperature changes. For each elevation, temperature (and pressure) is fixed in Altimeter and does not change. SLP on the other hand, does change with temperature.
How are you generating Altimeter? Do you have the Davis Vue console which can calculate SLP or Altimeter? Alternatively, Altimeter can also be calculated in software using WeeWX weather software. WeeWX can also upload Altimeter to CWOP.
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Altimeter uses a standard atmosphere model (International Standard Atmosphere or ISA for short) where temperature and pressure are fixed values at your specific elevation. See below:
Elevation: 6480.00 feet
ISA assumes completely dry air (no humidity)
ISA temperature @ 6480 ft: 2.16182°C
ISA temperature @ 0 ft (sea level) = 15°C
ISA pressure @ 6480 ft: 797.413 hPa
ISA pressure @ 0 ft (sea level) = 1013.25
Elevation offset: 1013.25 hPa – 797.413 = 215.837 hPa = 215.8 hPa (rounded)
This means that @ 6480 ft elevation, Altimeter should be about 215.8 higher than your current station pressure. A quick verification check with the NOAA/NWS Altimeter (setting) calculator indicates Altimeter = 1012.98 if we use the ISA pressure of 797.4 as your station pressure. The altimeter calculator subtracts 0.3 hPa/mb to account for the traditional 10 ft landing gear height for aircraft so that is why the answer is not exactly 1013.25.
If you do not have a Vue console, you can force a VP2 console to calculate Altimeter by setting elevation = zero. Keep in mind that this is a type of pseudo-Altimeter calculation using a fixed offset instead of the actual altimeter algorithm. Therefore, the fixed offset method will be most accurate when Altimeter is close to 1013.25. There is some drawbacks to consider with the fixed offset pseudo-altimeter method. At lower lows and higher highs, accuracy will start to drift.
You are at a very high altitude which poses a challenge to pressure reduction formulas – especially SLP. Here’s an excerpt from an American Meteorological Society article that might apply to your situation:
“Normally, station pressure is reduced to MSL only for stations with relatively low elevations above sea level (ASL). At higher stations, station pressure is usually converted to the height of the closest standard pressure surface.
In the United States, however, station pressure is reduced to MSL for stations as high as 2000 m ASL. In order to reduce the amplitude of the annual MSL pressure variation at stations situated above 305 m ASL (hereinafter referred to as “plateau stations”), a so-called plateau correction is applied at these stations. The correction increases reduced MSL pressure when the actual temperature at the station is greater than the yearly mean temperature at the same station, and vice versa. The correction can therefore change both magnitude and direction of MSL pressure gradients.”
Although your Davis console has a very good SLP algorithm, it is only an approximation of actual AWOS/ASOS SLP calculations so minor differences can be magnified at extreme elevations. Plus, when you add variable plateau effect corrections into the mix you may have difficulty matching SLP at your airport/METAR station at very high elevation.
Although you are pretty much at the maximum 2000 m upper limit for MSL calculations - If you are satisfied with your accuracy, that's great!
Sorry, I can’t help with the MADIS complaint about your sensor’s standard deviation. the screenshot shows the analysis has a somewhat jagged response but your sensor chart looks smooth enough. If your sensor is randomly jumping up a down over 1 mb or "stuck" (probability is that the sensor is failing/failed).
A common complaint by CWOP users is that neighbouring stations often do not set up their barometers correctly which impacts the MADIS quality check (in a bad way).
Definitions:
ASL – Above Sea Level
MSL – Mean Sea Level
SLP – Mean Sea Level Pressure
