[wxqc] Looking for help with Station - Odd shift in analysis

Ted Lum gladstonefamily73.net at tedlum.com
Thu Feb 18 18:13:45 CST 2016


I checked the airport and it definitely is Altimeter. No, you can't see 
what stations are in the analysis.

On 2/18/2016 6:43 PM, Chris Miller wrote:
> I had been using my phone as a comparison for a couple of weeks and 
> every time I checked it seemed to track, however that sample is small 
> and scattered so may have had the luck of the draw.  Discovering the 
> correction error in WUHU did account for a couple of mb.  The station 
> does track the nearby stations and has, when i get one of those artic 
> highs, all seem to gather together nicely so, crossing fingers, I hope 
> to see the model come back soon.  Mind you, in another month or so it 
> is libel to shift back due to the arrival of spring.  I think there 
> are a few SLP stations from the government side that may shift the 
> model line average??
> Oh!  While I think of it, is it possible to find out what stations are 
> used for the L3 checks and the model line? Mostly curious as to how 
> close they are and such.
> *From:* Ted Lum <mailto:gladstonefamily73.net at tedlum.com>
> *Sent:* Thursday, 18 February, 2016 07:50
> *To:* Chris Miller <mailto:c_miller_1 at hotmail.com> ; 
> wxqc at lists.gladstonefamily.net <mailto:wxqc at lists.gladstonefamily.net>
> *Subject:* Re: [wxqc] Looking for help with Station - Odd shift in 
> analysis
> No, the MADIS analysis line gets so crazy sometimes since it's so 
> sensitive to individual samples/readings.
>
> You may actually have a faulty sensor that is drifting. I know it's 
> not easy to do, but, I'd start by comparing the raw readings from the 
> station with another local, uncorrected, pressure sensor. Nothing 
> needs to be calibrated since you're looking at the delta over time; if 
> they differ by 2mb today, they had better differ by 2mb 5 days and 10 
> days from now... if not, you've got a very fundamental problem.
>
> On 2/18/2016 7:37 AM, Chris Miller wrote:
>> Thanks Ted,  I had been playing with the analysis period to escape 
>> the shifted data when I made corrections.  The best I have so far, 
>> with a short analysis period of 3 days, is still the 4 to 6 mb below 
>> the model line.  I was starting to wonder if the model has a large 
>> fixed period that it has to work through before I would see it shift 
>> down toward my setting.
>> *From:* Ted Lum <mailto:gladstonefamily73.net at tedlum.com>
>> *Sent:* Wednesday, 17 February, 2016 16:12
>> *To:* wxqc at lists.gladstonefamily.net 
>> <mailto:wxqc at lists.gladstonefamily.net>
>> *Subject:* Re: [wxqc] Looking for help with Station - Odd shift in 
>> analysis
>> The graphs are what they are in terms of date/time, but the default 
>> analysis period is 28 days. You can select a different period from 
>> the links at top of the page, or by specifying a specific number in 
>> the url.
>>
>> On 2/17/2016 4:04 PM, Chris Miller wrote:
>>> Ok.  I have set the pressure on the PEET station to 23.46 mb over my 
>>> local surface pressure.  I have let the station run for a while and 
>>> cross checked the device used to get the local pressure to the 
>>> station AV065 and CYYB and any measurement error corrected for.  I 
>>> discovered that WUHU, when set to QNH pressure to CWOP with the 
>>> altitude of the sensor set to 650 feet (643 feet plus sensor 
>>> height), that there is a correction that gets applied to the sent 
>>> data that is not visible on the display locally in the software.  It 
>>> appears that it has a temperature value in the math, if I read the 
>>> WUHU news group correctly.  I switched back to weather display with 
>>> no correction value in the software field and no altitude set in the 
>>> software and so far the data seems to match what is reported to CWOP.
>>> I have let the data run for a few days and my setting tracks the 
>>> output of AV065, CYYB, AR943 and CYWA with the expected stagger due 
>>> to weather pushing through.  The models for those stations show them 
>>> to be on, yet my model still shows me as being 4 to 6 mb low.
>>> Is there anything else that could be coming from the data supplied 
>>> that will skew the model so high?
>>> Also, is there a long delay, 3 to 6 months for example, before the 
>>> model would return to track the station after a burst of bad data?
>>> (I cropped down the email as it was getting a little long.)
>>> My station, model and nearest neighbours
>>> http://weather.gladstonefamily.net/qchart/AU770?date=20160217&addnl=AV065&addnl=CYYB&addnl=CYWA&addnl=AR943&Add+to+charts=Add+to+charts&.cgifields=addnl
>>> CYYB, its model and same stations
>>> http://weather.gladstonefamily.net/qchart/CYYB?date=20160217&addnl=AV065&addnl=AU770&addnl=CYWA&addnl=AR943&Add+to+charts=Add+to+charts&.cgifields=addnl
>>> CYWA, its model and same stations
>>> http://weather.gladstonefamily.net/qchart/CYwa?date=20160217&addnl=AV065&addnl=CYYB&addnl=AU770&addnl=AR943&Add+to+charts=Add+to+charts&.cgifields=addnl
>>> Chris
>>>
>>


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