PWS and WU Barometer Update

[aussiewmr]

Hi all,

Really getting into this weather stuff and cumulus - far more than I imagined I would

Anyway I ditched WOW and signed up for PWS and I immeadiatly saw an issue with barometer updates. In fact I have seen exactly the same issue on WU as well, so I am wondering where the problem actually lies.

Referring to the attached screen shot, PWS reports my sea level baro as 1017.3 at 0915, 0920, 0925 when in actual fact it was 1017.1. Now its not the old station vs seal level pressure issue. My station baro is actually 1015.7 (being 10 M asl). PWS is 0.2 mb to high for the same time as my console.

The other thing is that even though the baro is changing on my station by more than 0.1 mb, WU (and I suspect PWS) does not change with it for some minutes - could be 20 mins or nearly an hour. So why is this an issue, none other than the graphs look like big step changes when in fact they are not - the second screen shot shows that.

Both sites update every 5 mins. All other measurements like temp, humidity all seem to be good.

Anyone know whats going on here?

Cheers
Phil

PWS Site

PWS Baro Diffs.gif

WU Site

WU Baro Diffs.gif

[aussiewmr]

OK i think I have worked it out.

PWS and WU are both only changing in multiples of 0.3 to 0.4 mb (sometimes it changes by 0.3 other times it 0.4 mb).

Since both sites are American based, I figured that maybe the DB is only set to have a resolution of 0.01 Inches (Hg) which equates to 0.34 mb.

So I guess that's life and I am stuck with it. Probably need to look at running my own DB server to get history graphs working to a better res than 0.3 mb.

Cheers

[steve]

Like all of the sites which use the WU protocol, PWS Weather requires pressure to be sent in inHg. Cumulus sends it to 3 decimal places, which would be a resolution of about 0.03 mb, so presumably PWS Weather is only actually using 2 decimal places of the supplied pressure (about 0.3 mb).