I do urge that data from "personal weather stations" be taken with a grain of salt. These are not certified, calibrated instruments and they are often poorly placed.
What John says here is correct. I use one of the better personal weather stations, a Davis Vantage Pro2, but it does have its limitations. Like most of its ilk, the tipping pan rain gauge probably underestimates rainfall, especially in heavy downpours and in very light drizzles. Perhaps as much as 25 % underestimation is possible in such instruments, research has shown. (NWS tipping-pan gauges are much better designed.) Barometric pressure is not calibrated; one sets a value matching the nearest NWS station on a geographically uniform weather day.
However, this suits my purpose here on the farm. It gives me more reliable data than NWS does in MY field. We have significant microenvironment issues here and our rainfall quite often does not match that in the valley 2 km away (and down a few hundred meters). I also have an added, secondary thermometer buried 10 cm deep to track soil temperatures. And my manometer is set 2 m above the ground. Those are the values used by agricultural scientists. NWS mamometers are at 10 elevation and geologists measure ground temperatures 2 m deep. While my observed values might be off somewhat, the changes are extremely useful. Oh, I have a UV monitor so I know when its less dangerous to go out to do some work in the field. And I do tip my eye to the evapotranspiration losses the computer calculates.
It's better than a weather rock, John! Jim -- James R. Frysinger 632 Stony Point Mountain Road Doyle, TN 38559-3030 (C) 931.212.0267 (H) 931.657.3107 (F) 931.657.3108 On 2013-03-13 13:03, John M. Steele wrote:
Well, it is obviously a matter of opinion and we all have one. I have also used Weather Underground, and they are good. I don't dispute that. I do urge that data from "personal weather stations" be taken with a grain of salt. These are not certified, calibrated instruments and they are often poorly placed. After noting WIDE discrepancies in ones near my home, I disabled their display in Weather Underground, only letting it display nearest airport (the sites run by NWS). Up until some time last year (in the fall??) I would have agreed that WU had a better display. NWS greatly improved their scripts for their weather pages. For their "point forecasts" I prefer their page now (point forecasts are by zip code or small town). Their zone forecasts, at a county level, are still nothing to write home about. If you haven't looked at NWS lately, I recommend looking at the point forecast for your zip code vs Weather Underground and form your own opinion. See my earlier note if you can't figure out how to switch the NWS page to metric. WU does include the METAR, the raw weather observations broadcast to pilots. A coded text format, but they have a primer on how to read it. Sometimes it helps to see the raw data and units. Via a link at the bottom, NWS has a very nice tabular, hourly forecast for the next 48 h. In my opinion, it is worth having bookmarks to both for your base location(s). Which one you use most is up to you. ------------------------------------------------------------------------ *From:* "c...@traditio.com" <c...@traditio.com> *To:* U.S. Metric Association <usma@colostate.edu> *Sent:* Wed, March 13, 2013 1:18:03 PM *Subject:* [USMA:52511] Weather Forecasts Reference was made on this list by John Steele to the www.National Weather Service's forecast page (www.weather.gov). I would like to point out that the NWS site is quite an inferior source for such information. I would recommend instead Weather Underground (www.weatherunderground.com) as by far the best resource available, better even than Accuweather. Its metric usage is perfection, having been worked on by our own USMA meteorologist, Dr. Don Hillger. EVERYTHING is in SI units, if you set it that way under Settings (Metric instead of English units, as they are called there). Moreover, the amount of information far surpasses that of the NWS site, as thousands of local digital weather stations in backyards are included, with more data, lists, and graphs than you can imagine. Martin Morrison Metric Training & Education Columnist, USMA's "Metric Today"
