Topic: What Does the THW Index Mean?

[Bunty]

In WeatherLink what does the term THW Index Mean?  I may be wrong, but I somewhow got the impression that it's an indicator trying to get across in temperature wise a way for how the weather "feels".  Anyway, looking up the term on the Internet was of little, if any help.  Probably the THW Index needs renamed so it can be as well understood as the wind chill index and so won't be so off putting to web site visitors where the THW term is used.

[d_l]

Note: The WeatherLink software (version 5.2 through 5.5.1) offers a variable does not include
the sun term in its calculation. It shows the result as the “THW Index” or Temperature-Humidity-
Wind Index. This value indicates the “apparent” temperature in the shade due to these factors.

from http://www.davisnet.com/product_documents/weather/app_notes/apnote_28.pdf

[wxtech]

I post a "feels like" temperature on my site and banners.  I use VWS data.  So, the VWS tags used for that data are changed from wind chill during the winter, to heat index in the summer, to virtual temperature when it is appropriate. 
"Feels like" is a term that most visitors understand.
Davis help index description:  The THW Index uses humidity, temperature and wind to calculate an apparent temperature that incorporates the cooling effects of wind on our perception of temperature.
I wish that VWS also had the THSW (Temperature, Humidity, Solar, Wind) index that also incorporates solar in the equation.  Davis has that variable.
I'm using VWS Internet V13.01 p09

[sam2004gp]

I noticed that VWS 13.01 P9 has a "THW" and "THWS" index, but the values read zero for me.  Is this because I am using an OS WMR-968 station?

[mackbig]

I believe that value comes directly from Davis station.  So without the base number for THW and THWS, VWS will not display and none of the related calcs done by VWS will either.

The fields are listed in the 2007 manual (most recent I believe) as being not active. footnote 8
Release notes on 14.00p022 say these values are just for VP2.

Andrew

I noticed that VWS 13.01 P9 has a "THW" and "THWS" index, but the values read zero for me.  Is this because I am using an OS WMR-968 station?

[Anthony]

I noticed that VWS 13.01 P9 has a "THW" and "THWS" index, but the values read zero for me.  Is this because I am using an OS WMR-968 station?

You would be correct. The OS stations will not calculate this.

[LFWX]

I believe that value comes directly from Davis station.

This isn't a value that can be "read" from the Davis station, it is calculated by the station (for display on the console) and it is also calculated by the WeatherLink software. It is supposed to be something that was added to VWS, but it only works correctly for the THW Index, the THSW Index still doesn't work correctly (always shows the current real temperature). WeatherLink doesn't even show the current THSW and the last I heard from Ed (creator of VWS) the VWS THSW Index was not working because of a problem with the DLL from Davis.
You can, however, see the THSW plotted on a graph and it often goes below the THW when the sun isn't shining (same happens on the Davis display), so I don't think they have all the bugs worked out of this calculation.

[Sigdigit]

They definitely need to work on THSW index calcs, WL comes up with a much different one than that shown on console, particularly in winter.  Console seems to be much closer to what it actually feels like.  I brought this to Davis' attention.  They said it would be brought to programmer's attention and addressed if they ever get a chance to.

[SLOweather]

Does anyone have a pointer to the actual THSW equation/calcs?

[port1]

I agree with Andrew and Anthony.
The OS doesn't compute that value.
I wish it did 

Henry

[jruys]

Here is a link to a Davis document that has all of their calculations in it.  The THSW calculation is pretty complex, taking up a number of pages.  I used the calculations in a c# application that returned a result that was pretty close to what WL was, at least it was within a couple of degrees.
http://www.ruysfamily.com/WeatherDownloads/VPtech_Manual.pdf

[SLOweather]

Thanks! I've printed that out and will be poring over it tonight. I'm betting it will answer a LOT of questions I have, more than just the THSW.

Chris

Here is a link to a Davis document that has all of their calculations in it.  The THSW calculation is pretty complex, taking up a number of pages.  I used the calculations in a c# application that returned a result that was pretty close to what WL was, at least it was within a couple of degrees.
http://www.ruysfamily.com/WeatherDownloads/VPtech_Manual.pdf

[d_l]

Here is a link to a Davis document that has all of their calculations in it.  The THSW calculation is pretty complex, taking up a number of pages.

Thanks! That looks like it has more complete explanations/formulas than the various application notes.  So the application note for the derived variables maybe a condensed version of that reference manual.