Barometer deviation problems and CWOP QC

Don’t know if this will help. What I did was watch the quality reports for a week then adjust the station. I did this for a couple of weeks and it seemed to work. Maybe my theory is wrong but…

Your pressure looks a lot like mine does most of the time, but the last few days mine has been reading higher than the ANALYSIS.

Notice that I am still getting a 99% rating even though I am not lined up right on the RED line? That’s cause the TRACK is still right on with the MADIS changes.

During a typical Spring/Autumn-like day, my temp graphs look a lot like yours does right now, but when we have these winter storms coming through, all bets are off. In my case, those living within a mile of my station would laugh at the MADIS Temp and Dewpoint graph. The BLUE graph is where our temps were today. We still have a foot of un-melted snow on the ground. I wish it got up to 49 today! We might have gotten some melting. :wink:

Nice write up…My main thing is I would like to know what stations I’m getting analyzed with. If the MADIS/CWOP system brings every station to a commom denominator for every value then I’ll except the error.

Depending on who I’m analyzed with, I should have a higher baro reading. My day and night temp will vary since I’m on a southern side of a mountain facing a valley.


I agree!

It would be nice if we KNEW WHO we were being compared with! Still not really sure why NOAA makes that some kind of deep dark secret. 8O

Based on the swings/spans in temp and dewpoint I see on my ratings, I have to assume that I am getting compared to stations in Oakhurst Ca. which is 8 miles west and more importantly…1800 feet LOWER in elevation! #-o

It doesn’t help that I have two neighboring stations that are consistently TOO WARM in their temp readings.

If there is any way you can borrow a high end barometer just to use for a few days, I would highly recommend it. Once you dial in your VP2 to match, you shouldn’t need to mess with it anymore.

My VP2 was VERY close right out of the box. I adjusted my VP2 pressure a total of 1.0 millibar UP. (Make sure you nail your elevation as close as possible before doing anything. This can have a HUGE effect on your initial setting and accuracy)

Here is a link to the analog “Fortin Style” mercurial that I have:

Model 453X

Unfortunately, it is getting nearly impossible to buy these anymore because of all the restrictions on MERCURY. Princo stopped making all Mercury based instruments back in 2007, I’ve had my “Princo” for years. That is why I said BORROW if possible. :wink:

I’ll try to borrow one. Right now my station is adjusted UP 2.86 mb. Elevation is close as possible (Handheld GPS/Google Maps). Off subject — What I like to see is a network of PWS’s in realtime ± 5 minutes, so you can see what is actually going on at the surface. I always believed that what is going on in the current time is better than any model.

I totally agree!

You might want to check on Weather Underground and find as many local stations sending with RAPID-FIRE as possible. Separate them out from the rest and track them for a few days. If you are handy with programming, perhaps you could write a little network app that gathers their data and compiles it into a graph like CWOP does with their stations?

I send my Wunderground data packet every 2 seconds using Rapid-Fire, but I am the only station up here at Bass Lake that is currently using this great new Wunderground option! In fact, I think only two other stations up here in the Central/Southern Sierras out of a few dozen are using Rapid-Fire. I assume it must be a limitation of their weather software, or they simply don’t know they have this new option.

The formula for SLP takes raw sensor pressure, elevation, temperature, and humidity as inputs, and from this it calculates the sea level reduced pressure. The altimeter formula only takes raw sensor pressure and elevation as inputs. So, given a specific elevation and a specific raw sensor pressure, the altimeter formula will always produce the same altimeter value. But given that same elevation and raw pressure, the SLP formula can produce a range of values over the range of possible temperature and humidity inputs. That is where the drift comes from. For the same elevation and pressure, SLP will produce a different result on a cold day than it will on a warm one.

OK, I understand that now. I think what confused me is I was trying to make the Davis display read correct. After I changed to the WD CWOP setting and use that setting also for WD and my website, everything looks good. The Davis display has a different reading, but I am assuming that is the raw baro not the corrected since WD can not change the Davis display. I will watch this now for a few days and see how things track on the CWOP QC page. My Temp and Hum/Dew on CWOP has always been good and tracks very well. Maybe now I have the Baro setup correct and it will also track correctly. Thanks for the explanation.

EDIT: 72 hours later and everything looks good, tracking very well now.

EDIT: Seems everything is going good now. I am tracking very well with the local airports now. Average deviation is around 0.4 millibars now. I can deal with this much better. Thank you guys for your input, it did help quite a bit.

Interesting read this thread. I don’t have a barometer issue as I track within .05 -1mb of the 5 stations around me all are FAA/NWS. Only PWS station in the area. But I seem to get bad reports about humidity and temperature. Here is where the microclime kicks in. I am 50 feet about Salt water and in mountainous terrain. The major channel both for water and wind is se to nw. Gladstone last time I wrote to him about his program says he compares me to the airport which is 5 miles away on a different island. When the wind blows they are always cooler as the wind has come over 100 miles or so of 40 degree water and ice fields. This tend to make PAKT temps a little lower then wher eI am sheltered from the NW winds. Gladstone does not seem to take this into account. I still have a old 20 year old davis monitor and it shows the same temps my OS system gets. So I believe what I see here and not what he says with his program. A morning check of the metars around me 100 mile range shows that I am in the ballpark with everyone around me. Being a mountainous marine enirometer can be a challenge with weather with out a bad anyaltical program thrown in by the bad data it gets. What I did learn it seems that they use the government states around you to aalysis your data. Looking at the charts they have it seems to be a national average more the just your area.