Trixology
WeatherCat => WeatherCat Feature Requests => Topic started by: Steve on February 13, 2012, 06:28:51 PM
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I would like to request that a TAG be added to WeatherCat's list of tags and AppleScript dictionary to display THSW Index (Temperature Humidity Sun Wind) for weather stations that support this feature. A Davis VP2 or VantageVue with a solar sensor is able to calculate this index and display it on the console. The THSW Index is an arguably more accurate indication of "Feels Like..." than the Heat Index.
THSW Index is described on page 21 and 42 of the Davis Console Manual:
Temperature/Humidity/Sun/Wind (THSW) Index
The THSW Index uses humidity and temperature like for the Head Index, but also includes the heating effects of sunshine and the cooling effects of wind (like wind chill) to calculate an apparent temperature of what it ?feels? like out in the sun. The THSW Index requires a solar radiation sensor.
If this TAG is added to the WeatherCat tags and AppleScript dictionary, the results can be added to web pages and Twitter posts.
Thanks for your consideration,
Steve
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I second it, but the Vp2 nor the Vue I dont think output the THSW index in its loop packets.
If Stu where to integrate it into WC he would have get the index online and program it into WC, it would then apply to all weather station types.
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Thanks folks. I'll add it to the 'things to look at' list.
Cheers,
Stu.
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Dear Steve, Tim, and WeatherCat fans,
Sorry to sound negative, but I can't say that I feel this sort of thing is the best use of Stu's time. I've made my "lament" before, but I worry that the attempts to come up with these "feel like" metrics can't cope with one insurmountable obstacle: fickle human psychology! :o The THSW Index may have good science as far as human physiology, but someone is always going to disagree as folks already disagree with other metrics. I can't help but adapt an old saying to express my feeling about this:
A man with a thermometer knows the temperature, a man with multiple heat indexes - is never sure.
Given that Stu has a lot of catching up to do, sure this should be on the to-do list, but maybe not too high on the priority list. WeatherCat is now seriously behind on things like supporting the latest generation of weather stations out there. We need to be patient and allow Stu to put his time where it is most likely to get a return on his efforts . . . . in particular, these kind of returns . . . . (http://www.canebas.org/Weather/LWC_forum/Custom_emoticons/dollar.gif)
Cheers, Edouard
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Dear Steve, Tim, and WeatherCat AppleScript fans,
Actually, I just had another thought on this one . . . .
I would like to request that a TAG be added to WeatherCat's list of tags and AppleScript dictionary to display THSW Index (Temperature Humidity Sun Wind) for weather stations that support this feature. A Davis VP2 or VantageVue with a solar sensor is able to calculate this index and display it on the console. The THSW Index is an arguably more accurate indication of "Feels Like..." than the Heat Index.
Actually if all you want is a web tag and don't need this updated too often, it might be possible to generate this value in an AppleScript instead. I have no idea what the formula looks like, but if it isn't too "hairy", AppleScript might be able to do the computation.
However, if you suddenly start looking my way . . . . you'll still need to be patient! (http://www.canebas.org/Weather/LWC_forum/Custom_emoticons/patience_emoticon.jpg). I really need to take the existing AppleScripts "into the shop" for a serious overhaul. [computer] As they stand now they are driving you'all and me crazy!! :o
Cheers, Edouard [cheers1]
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I second it, but the Vp2 nor the Vue I dont think output the THSW index in its loop packets.
If Stu where to integrate it into WC he would have get the index online and program it into WC, it would then apply to all weather station types.
Ah, so the display in the console is getting generated by the console itself, not what's coming from the ISS. Wonder what formula Davis is using?
Dear Steve, Tim, and WeatherCat fans,
Sorry to sound negative, but I can't say that I feel this sort of thing is the best use of Stu's time.
Well, he asked for things we'd like to add on a wish list. I wasn't asking for it before release, next version, or whatever. He asked us for ideas. :shrug:
As far as your objection to the validity of heat indexes, I remember you stating that view before when I was asking about creating it for LWC's Twitter feed. Regardless of whether the science is valid or not, here in humid middle America, it is prominently posted on weather reports on TV, radio, etc. Lots of "Be careful out there folks. It is 93˚ out, but feels like 117˚" It is a big part of what viewers want to know about current conditions.
I never did find the formula when I looked before. I'll write my contact at Davis and see if I can find out!
Steve
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Howdy Steve and WeatherCat fans,
I second it, but the Vp2 nor the Vue I dont think output the THSW index in its loop packets.
Ah, so the display in the console is getting generated by the console itself, not what's coming from the ISS. Wonder what formula Davis is using?
Actually I don't know anything about VP-2 "innerds" but if I had to guess, it is that THSW isn't one of the channels that Davis makes available to folks who write weather software. I thought Stu had "cleaned out" what Davis had to offer back in the Spring. So if the console computes the value - it isn't nice about sharing. :(
Well, he asked for things we'd like to add on a wish list. I wasn't asking for it before release, next version, or whatever. He asked us for ideas. :shrug:
I think you are right that it needs to get into WeatherCat someday. I just think that indeed you'll need to be a little patient (http://www.canebas.org/Weather/LWC_forum/Custom_emoticons/patience_emoticon.jpg). We had another question on MacWeather about LWC support of a modern station (the Oregon Scientific WMR88). That station has a retail price of $130. While we swear Davis is better (especially with our commisions ;) ), not everybody can afford this. If Stu is going to regain his place as #1 Mac Weather software with WeatherCat, he will have to hustle a bit to support some more "reasonably priced stations."
So I wasn't trying to say never implement THSW, but perhaps it would have to wait while under some other things get taken care of first.
Also, Stu may need to think a little bit about all these indexes. At the risk of another annoying suggestion, perhaps Stu should have a preference to allow people to chose just one "heat index" on the gauges. Otherwise the gauges display ends up being a bit cluttered. I would hope that folks could settle on one preferred metric to compute heat index.
As far as your objection to the validity of heat indexes, I remember you stating that view before when I was asking about creating it for LWC's Twitter feed. Regardless of whether the science is valid or not, here in humid middle America, it is prominently posted on weather reports on TV, radio, etc. Lots of "Be careful out there folks. It is 93˚ out, but feels like 117˚" It is a big part of what viewers want to know about current conditions.
;) I'm sorry, if I have to bake in a horrible drought [sun2] - you'll have to sweat it out!! [sweat2] At the very least you should share some of your summer rains!! [rainy]
Seriously, perhaps before the summer heat sets in, at least an AppleScript could be cobbled together so that WeatherCat websites have this sort of info.
I never did find the formula when I looked before. I'll write my contact at Davis and see if I can find out!
That certainly will help! That might get Davis to change their stations to allow one to get that data off the consoles. That would be much easier for Stu!
Cheers, Edouard [cheers1]
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I'll let Stu prioritize the suggestions. He asked, so I made a suggestion.
I've re-searched Google and I guess I did find some info. There is an 8-page discussion on how it should be calculated on the Weather Display forum, another discussion on the wxforum, etc. All agree that the data does not come from the feed, and that apparently it is a quite complex set of calculations based not only on temp, humidity, sun, and wind, but also takes into account time, latitude, longitude, and normal expected solar readings for your location.
Here's a bit on HOW it is calculated, but not the calculation itself:
THSW Index: Same concept as for the THW index, but THSW index includes the effects of the sun's solar energy and is the most useful measure of how it would feel if you were standing directly in sunlight. Parameters Used: Temperature, Humidity, Solar Radiation, Wind Speed, Latitude & Longitude, Time and Date. Like Heat Index, the THSW Index uses humidity and temperature to calculate an apparent temperature. In addition, THSW incorporates the heating effects of solar radiation and the cooling effects of wind (like wind chill) on our perception of temperature. The formula used to calculate THSW by our Vantage Pro 2 Plus system was developed by Steadman (1979). The following describes the series of formulas used to determine the THSW or Temperature-Humidity-Sun-Wind Index. Thus, this index indicates the level of thermal comfort including the effects of all these values. This Index is calculated by adding a series of successive terms. Each term represents one of the three parameters: (Humidity, Sun & Wind). The humidity term serves as the base from which increments for sun and wind effects are added.
HUMIDITY FACTOR:
The first term is humidity. This term is determined in the same manner as the Heat Index. This term serves as a base number to which increments of wind and sun are added to come up with the final THSW Index temperature.
WIND FACTOR
The second term is wind. Depending upon the version of firmware or software, this term is determined in part by a lookup table (for temperatures above 50?F) and in part by the wind chill calculation, or uses an integrated table that is used both for calculation of this term and for wind chill. With this in mind, the following criterion apply with later versions referring to Vantage Pro2 console firmware revision May 2005 or later or WeatherLink version 5.6 or later:
? At 0 mph, this term is equal to zero.
? For temperatures at or above 68?F and wind speeds above 40 mph, the wind speed is set to 40 mph. For later versions, there is no upper limit on wind speed.
? For temperatures at or above 130?F, this term is set equal to zero. For later versions of this algorithm: WeatherLink uses 144?F as the threshold; Vantage Pro2 console firmware 143?F. This is based on a best-fit regression of the Steadman 1979 wind table. The differences are reflective of the higher resolution used in the WeatherLink software.
? For temperatures below 50?F (later versions use the new wind chill formula result here (calculate the wind chill increment using the difference between the air temperature and wind chill)):
? For the earlier display console versions and WeatherLink version 5.0 or 5.1: use the wind chill calculation as the base temperature.
? For the WeatherLink software (versions 5.2 through 5.5.1): use the new heat index formula (as described in the heat index section) as the base temperature and calculate the wind chill increment using the difference between the air temperature and wind chill (which is always a negative number). The resulting value is the wind term, which will be added to the humidity term and subsequently the sun term as indicated below. 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.
SUN FACTOR
The third term is sun. This term, Qg, is actually a combination of four terms (direct incoming solar, indirect incoming solar, terrestrial, and sky radiation). The term depends upon wind speed to determine how strong an effect it is. The value is limited to between −20 and +130 W/m2 in the Vantage Pro2 console firmware and WeatherLink software versions 5.6 or later.
REFERENCES
Steadman, R.G., 1979: The Assessment of Sultriness, Part II: Effects of Wind, Extra Radiation
and Barometric Pressure on Apparent Temperature. Journal of Applied Meteorology,
July 1979.
"Media Guide to NWS Products and Services", National Weather Service Forecast Office,
Monterey, CA, 1995.
Quayle, R.G. and Steadman, R.G., 1998: The Steadman Wind Chill: An Improvement over
Present Scales. Weather and Forecasting, December 1998
I wrote to the contact who is the editor for the newsletter, and copied the PR guy I talked to on the phone. I let them know this is for a new software package under development.
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I agree Steve, Stu asked and you said what you would like and I backed you up.
I just think that indeed you'll need to be a little patient
There is no pushing or people being impatient here, he asked and simply we replied that is all.
It is up to what Stu what he implements and when he implements it (if he does..)
He is asking for feedback and all we are doing is replying, there wasnt a need to bite our heads off.
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Hi Steve, Tim, and WeatherCat fans,
*Heavy Sigh* :(, sorry gang . . . I know my opinion carries a lot of weight, but I wasn't trying to sound like a bully.
I agree Steve, Stu asked and you said what you would like and I backed you up.
I just think that indeed you'll need to be a little patient
There is no pushing or people being impatient here, he asked and simply we replied that is all.
It is up to what Stu what he implements and when he implements it (if he does..)
He is asking for feedback and all we are doing is replying, there wasn't a need to bite our heads off.
I sure wasn't trying to sound like that. I hope you can understand that I was simply trying to rationalize what the priorities might be. In a perfect world not only would Stu have the time to implement this metric, but it would be standardized and well accepted. The trouble is that Stu only has so many hours in the day. So realistically, it going to be a while before he can get to this.
I hope we would all agree that Stu needs to catch up with the feature-set of his rivals which does include this I believe. Still I think that if we made a list of the features found in say WeatherSnoop that aren't in WeatherCat right now . . . well, where you you'all think THSW fits in the queue?
So again sorry, but I was trying to put your suggestion in that context. Indeed anything you can do to help Stu eventually implement this is a good idea. Also if the calculations are manageable, perhaps an AppleScript can be put together as a stop-gap. Stu has never incorporated an AppleScript into WeatherCat but he is most welcome to do this and I would hope that would be less work than having to come with everything from scratch.
Indeed if we can help Stu do some of the things we want, it is that much closer to being done.
Cheers, Edouard
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Still I think that if we made a list of the features found in say WeatherSnoop that aren't in WeatherCat right now . . . well, where you you'all think THSW fits in the queue?
I'm not trying to compete with other apps, but if you want to compare, the two largest players in the weather software business, WeatherLink and Weather Display both have the THSW Index.
I wasn't trying to start a debate on the value of the Index or where it should be in Stu's list of priorities! I was just doing as asked (bold added by me):
Hello folks,
Please use this forum to tell us what features and things you'd like to be able to do with WeatherCat in the future.
I won't add any more feature requests until WeatherCat works with every system out there and has every feature available on every software package... :-X
I know that's not what you mean, but it sure keeps coming across that way.. ;)
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Cool down, WeatherCat friends! Stu asked for features and Steve gave him a feature - that's it. If it would be processed or not, no one will decide this except Stu.
I won't add any more feature requests until WeatherCat works with every system out there and has every feature available on every software package... :-X
In my opinion Stu is happy about requests - if they are possible to realize, that's another story. And now I'm opening a beer (it's pretty late here on my side): Cheers! [cheers1]
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Hi Gang,
I'm sure sorry I opened my mouth on this one. I was simply trying to help folks calibrate expectations. Certainly Reinhard is hitting the nail on the head. Stu most certainly asked for suggestions and he will decide what the priorities are.
I know that's not what you mean, but it sure keeps coming across that way.. ;)
However, if this is something you'all do free strongly about, you can most certainly nudge it up the priority queue by providing Stu with a little more info about it. If someone could come up with the formula that would be another quantum leap toward implementation.
I had another thought this morning. This is the sort of thing that could be implemented as a WeatherCat plug-in with very little user-interface required. I would very much like to "cut my teeth" on a very simple WeatherCat plug-in. So this might be a very good "trainer project" for me or anyone else bold enough to learn Stu's plug-in architecture.
Asking Stu to make a worthwhile improvement is good - but making that improvement within easy reach of what Stu (or someone else) can implement is much better!
Cheers, Edouard [cheers1]
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Sorry for the previous snarky reply, but it is really frustrating for me to repeatedly say that Stu asked for us to suggest things and then repeatedly getting it shoved aside. I *know* it isn't as important as some things. But I keep saying that Stu asked for ideas, and I simply suggested one.
However, if this is something you'all do free strongly about, you can most certainly nudge it up the priority queue by providing Stu with a little more info about it.
I have, and I am! Above I provided the science and methodology to it, and I've received a reply from the contact at Davis that she's forwarded my request on to the engineers. She said it would be a couple of days before they get back to me, but I don't think Stu will be ready to work on this in the next day or so. So I'm doing what I can to provide what's needed.
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Wow, well this thread went a little sideways!
Folks, don't worry about what is and isn't doable - in fact, the more impossible it might seem, the more I'm likely to like it :)
This forum will aid future development - some stuff might make it in and some won't - but it all helps guide the development.
I'm sure if I developed just what I want, a lot less people would be interested, so I need to know what you want to see.
I'll let you into a secret - apart from WeatherLink and HeavyWeather (which came with my first WS2300), I've never looked at another Weather program so have no idea what they can or can't do - I'd rather be guided by what people want rather than what's currently available.
Cheers,
Stu.
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I received a reply from my contact at Davis. The engineer she talked to said that Davis' interpretation of the THSW Index uses proprietary formula, and they are not able to share it. He did say that it requires a quite complex relational database and the calls to the database probably wouldn't be scriptable.
I'll keep looking. I did find a reference to a guy that was trying to program it for his web site, and had a 45 page set of information to convert into a database.
Steve
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Hi Steve and WeatherCat fans,
The THSW index sounds even more miserable to compute than the Penman-Monteith model of evapotranspiration. Still, Davis allows weather station software to get those values off of a VP-2. Something seems out of whack here. If this computation is as miserable is it appears, I would be surprised if other weather station software could be computing this value on their own - especially if there is no standard formula. The THSW index can only be computed on a weather station that has a solar sensor. So as far as I now, the only stations within reach of serious amateurs is the Davis Vantage Pro-2 line. Tim, are you sure the VP-2 isn't able of sending this data to weather station software? If Davis's own WeatherLink is displaying the data, wouldn't it be simpler to fetch the data from the station console than to try to replicate the very same calculations on the PC?
Thanks Steve for going to so far to get Davis's input on this. Sorry to impose, but could you perhaps ask the Davis engineers if the THSW values can be simply downloaded from the console like the evapotranspiration values? If it is displayed on the console, why wouldn't they make it available to software? If there was a way to get the THSW Index off of the VP-2 console that is a much simpler job for Stu to incorporate it into WeatherCat. Since practically speaking, the only stations that could compute THSW Index are VP-2s with a solar sensor, trying to compute the value within WeatherCat is a waste of time.
Thanks again Steve for exploring this matter. [tup] Certainly not as simple I would have imagined it. Kinda sad to think companies would have proprietary formulas to compute values like this. Oh well.
Cheers, Edouard [cheers1]
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Edouard,
The THSW Index is calculated within the console for display on its own screen but is definitely not available via the data streamed from the console. This has been examined and tested by various sites, and people have been in contact with Davis confining this elsewhere. The WeatherLink software compiles the index within its programming for display on WeatherLink's screen and web tags. WeatherData is where the 45 page database info came from, and they've compiled it into a database that Weather Display uses to calculate its iteration of the THSW Index. In comparisons, the Davis and WeatherD numbers don't always match, but they are close. No one knows how Davis calculates it, so WeatherD does its best to replicate the results.
So WeatherLink only works with Davis stains that provide temp, humidity, solar , and wind readings, and WeatherD works with any station that can provide the same, be it a Vue with a separate solar sensor, an assortment of individual sensors, or a Davis VP2 with solar. WeatherD is much more flexible as towhee it gets its information to calculate and display.
So yes, with WeatherCat's current capability, it would seem a very limited potential audience would want this feature, which would most likely put it at the bottom or not even on Stu's priority list.
Regards,
Steve
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Hi Steve and WeatherCat fans,
Well, you've definitely done all that you could. Thanks for trying! [tup]
Certainly most unfortunate that Davis has handled things in this way. :(
Cheers, Edouard
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Perseverance wins the day!
Attached is the THSW Index formula and look-up table as calculated by Davis for the VP2 Console and in WeatherLink software. This is from a previous version of the AN-28 Derived Weather Variables (also attached.) Now, what to do with it is anybody's guess, as it is way beyond my simple math skills.
If you decide to add this to some future version of WeatherCat, Stu, it would be a nice feature. If not, I completely understand and appreciate the effort involved.
Thanks,
Steve
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Hi Steve and WeatherCat fans,
Attached is the THSW Index formula and look-up table as calculated by Davis for the VP2 Console and in WeatherLink software. This is from a previous version of the AN-28 Derived Weather Variables (also attached.) Now, what to do with it is anybody's guess, as it is way beyond my simple math skills.
Well, it may be well beyond my math skills too . . . but I'm a sucker - I'll download anything!! :P (Not!! [wink])
However, making a quickly cruise though everything and finding some interesting stuff like a discussion on how Davis computes rainfall (you thought it was obvious, but there are some interesting details.) I don't see the killer formula. ???
Instead both documents insist you need to get your grubby paws on this paper:
Steadman, R.G., 1979: The Assessment of Sultriness, Part II: Effects of Wind, Extra Radiation and Barometric Pressure on Apparent Temperature. Journal of Applied Meteorology, 1979
If you decide to add this to some future version of WeatherCat, Stu, it would be a nice feature. If not, I completely understand and appreciate the effort involved.
So the plot remains uncertain. I didn't see anything that couldn't be swallowed by an AppleScript, but without the key formula . . . kinda stuck.
On the other hand this is very good news generally. That paper has to be available at any university and clearly the THSW index does have a solid academic basis that isn't owned by anybody. So it shouldn't be a problem to incorporate this index into WeatherCat. Stu will have to "use his connections" go get hold of this paper, but I assume that isn't beyond someone who actually can get cats to do all the coding!! [cat] After all managers have to earn their keep every now and then!! 8)
Cheers, Edouard [cheers1]
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THSW=Humidity + Wind quotient (from the look-up table based on temp) + Sun (which is Q1+Q2+Q3+Q4 as calculated on the third page) Easy Peasy! :D
Both just refer to the Steadman formula as what it is based on.
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Howdy Steve and WeatherCat fans,
It's early in the morning here so . . . . [coffee]
THSW=Humidity + Wind quotient (from the look-up table based on temp) + Sun (which is Q1+Q2+Q3+Q4 as calculated on the third page) Easy Peasy! :D
Golly, I just went over the documents again and I don't see that formula jumping out at me . . . . however . . . . see above! [coffee]
Still, I have enough brain power (if brains have anything to do with it) to type the titles of the Steadman papers into Google and . . . . let Google do the work!
I'd attach the two papers here, but they are PDF files that exceed the 1024KB size limit. So I'll just email them to Stu. If anybody else want to take a gander, let me know and I'll drop them in the email for ya'!
Cheers, Edouard [cheers1]
P.S. Thanks Steve for doing all this digging around! [tup] I've certainly learned a lot about the THSW Index and there is an added bonus with all those interesting details on the VP-2 in the supporting document. Great Job!! [bounce]
P.P.S. I repeat . . . . [coffee]
Here are (after all) the download links for your all:
Steadman, R.G., 1979: The Assessment of Sultriness, Part I (http://www.climateknowledge.org/heat_waves/Doc1006_Steadman_Heat_Stress_Index_JApplMet_1979.pdf)
Steadman, R.G., 1979: The Assessment of Sultriness, Part II (http://wonder.cdc.gov/wonder/help/Climate/Steadman1979.PDF)
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It doesn't give the formula as I wrote it above. But in the 4th paragraph is says "The index is calculated by adding a series of successive terms. Each term represents one of the three parameters: (Humidity, Sun & Wind)." And then goes on to tell how each term is derived and/or calculated.
Steve
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Got them, thanks folks [tup]
Stu.
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Howdy Steve and MacWeather fans . . . .
It doesn't give the formula as I wrote it above. But in the 4th paragraph is says "The index is calculated by adding a series of successive terms. Each term represents one of the three parameters: (Humidity, Sun & Wind)." And then goes on to tell how each term is derived and/or calculated.
And you expected me to see that before coffee!! [coffee]
Okay, okay, I got it now!
Cheers, Edouard [cheers1]