[wxqc] Dew Point Error for CW6532 Tucson

Tue Oct 10 09:32:32 CDT 2006

John,

I faced the same exposure problem as you. In my opinion it's more important to provide to MADIS accurate temperature/dewpoint data, etc. than wind data. You should buy the fan aspirated temperature shield kit if you can, it's only $84.00 at Provantage.

The stock temperature shield that comes with the #6152 Vantage Pro2 is very inaccurate (up to +6 deg. F) at times, especially during high sun angle times when there is little wind.

By the way the wireless wind vane/anemometer option is $106. I had to buy both to get accurate readings on my oak tree laden property.

Take Care,
Thomas F. Giella, KN4LF
Retired Meteorologist & Space Plasma Physicist
Lakeland, FL, USA
flycylone at tampabay.rr.com

NWS Tampa Bay, FL SKYWARN Observer #POL-10A
CWOP Station #AR692/KN4LF

Live Lakeland, FL Weather Observations: http://www.kn4lf.com/index1.html
Lakeland, FL Daily Climatological Weather Data Archive: http://www.kn4lf.com/kn4lf22.htm
September 2006 Lakeland, FL Daily Climatological Weather Observations http://www.kn4lf.com/kn4lf63.htm
Florida/US Raw Weather Forecasting Resource Links: http://www.kn4lf.com/kn4lf13.htm
Man Induced Climate Change Refuted: http://www.kn4lf.com/globalwarminglie.htm
New Scientific Evidence for the Existence of God: http://www.cosmicfingerprints.com/audio/newevidence.htm 

  ----- Original Message ----- 
  From: John James 
  To: Discussion of weather data quality issues 
  Sent: Tuesday, October 10, 2006 2:18 AM
  Subject: Re: [wxqc] Dew Point Error for CW6532 Tucson

  ...days passed......

  Okay, I read the document, and another that was mentioned yesterday. 
  Both are somewhat helpful, but neither really does any weighting. In 
  the CWOP document, I can play with the location of my temp / rain 
  sensor and just about get an equal score regardless of which option I 
  choose. The Vantage Pro 2 is not a unimount system:  I can separately 
  mount the anemometer up on the roof by itself. If I do that, however, 
  I still leave my temp / rain sensor in the shadow of some trees - 
  probably fine for temp, but definitely shorting me when it comes to 
  most rain situations. I can move the sensor to the roof and probably 
  get a great rain figure, but then have to deal with the roof 
  affecting the temp readings.

  So, here's my practical question: currently, most of my readings are 
  wrong, and to make any fix I either need to buy the property next 
  door (very pricey!), or I need to buy some weather hardware. I could 
  buy another wireless transmitter and move the anemometer to the roof 
  by itself. I could buy a fan / power unit and make my temp with 
  radiation and UV shielding and make it fan aspirated. Which would be 
  preferrable?

  //John

  At 04:51 AM 10/4/2006, you wrote:
  >John,
  >
  >Yep, that is the problem with a unimount system.  Precip and temperature
  >are probably the most valuable for climate and hydrologic
  >considerations.  Wind and temperatures are more important for weather
  >prediction (modelers need "good" surface winds, e.g. not buried in the
  >canopy).   We recommend that people put their temperature and rain gauge
  >near 2 meters/5 feet and the anemometer at 10 meters/33 feet or above
  >the canopy, obviously; this implied separating the sensor package.
  >
  >For folks who must compromise (almost everyone does), we have a table in
  >the CWOP Guide that considers typical siting option limitations that
  >home owners encounter:
  >http://mywebpages.comcast.net/dshelms/CWOP_Guide.pdf
  >
  >
  >Dave
  >CW0351
  >
  >John James wrote:
  >
  > > At 08:13 PM 10/3/2006, you wrote:
  > >
  > >>
  > >> The first thing that catches my eye is that you have the temp/dpt
  > >> attached to a 6 ft. sensor from your rooftop (not familiar with the
  > >> term parapet, so maybe I'm wrong). While this is fine for the
  > >> anemometer and even the rain gauge, the temperature/dpt sensors
  > >> should be located at 2m off the ground (5-6 feet). Very sharp
  > >> inversions can set up at night, on the order of 5-10F within 30-40
  > >> feet of the surface, especially where terrain and standing water
  > >> bodies are an issue. Likely you're sampling a "different airmass"
  > >> above your roofline than you would be closer to ground level.
  > >>
  > >> Evan
  > >>
  > >>
  > >
  > >
  > > This brings up something I've been wrestling with a bit. I have a
  > > station up at my cabin that has been giving incorrect readings. I have
  > > a two story house and a somewhat wooded area in both front and back of
  > > my house. I don't have a very good clearing for wind, and was going to
  > > move the anemometer to the roof, but I don't think I'm getting good
  > > rainfall readings either due to the trees. I was thinking of moving
  > > the entire station to the roof, but knew that would alter the other
  > > readings. The unit is a Vantage Pro 2 Plus. I get the feeling I'm
  > > wrestling with which measurement I want to be more incorrect.
  > >
  > > //John
  > >
  > >
  > > 
  > ------------------------------------------------------------------------------
  > > John W. James
  > > CW4661, CW4663
  > > Web:  < http://www.jameshillfarm.com/>
  > >
  > > Current weather conditions:  <IMG
  > > SRC="http://www.jameshillfarm.com/images/WeatherStripJamesHillFfarm.jpg">
  > >
  > >------------------------------------------------------------------------
  > >
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  ---------------------------------------------------------------
  John James
  mail:  jjames at jameshillfarm.com  <mailto:jjames at jameshillfarm.com>
  Current 
  weather:  http://www.jameshillfarm.com/images/WeatherStripJamesHillFarm.jpg

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