Humidex Webtags

avoorpool · **Posted:** Sat Jun 09, 2012 10:49 pm

Hi Steve,

You might think: This must be a question from Canada!!
Indeed

For several reasons, we're dealing with the Humidex factor rather than the Heat Index. (currrently we see humidex values of 30+ C while the Temp is just around 24 C, simply because of high humidity levels coming in a N-E stream directly from the Gulf of Mexico. Since Heat Index deals with only 27 + C, I feel we don not get the correct information (how we really have to suffer

!)
Is there a way to add another humidity tag e.g <#humidexTH> and/or <#RecentHumidity ...>.
Since summer is around the corner and we often see Humidity levels of 60 - 75% in Toronto , temperatures can be extraordinary :!:

(I've attached a screen shot from my Tv last year in July (not manipulated!!) so you'll get an idea why Humidex info is important overhere!!!
Thanks,

Cheers,

Arthur
http://altonaweather.host22.com

steve · **Posted:** Sun Jun 10, 2012 8:18 am

avoorpool wrote:

Is there a way to add another humidity tag e.g <#humidexTH> and/or <#RecentHumidity ...>.

There's an enhancement request for additions to humidex handling, so one day I may well get around to doing it.

avoorpool · **Posted:** Sun Jun 10, 2012 2:18 pm

Thanks Steve.
For the next 3 - 4 month it's gonna be a "hot" issue here in Toronto

Even when summer is still 2 weeks away, we're already dealing with +38 C values today (June 10...!!)

Cheers,

Arthur

duke · **Posted:** Sun Jun 10, 2012 2:38 pm

avoorpool wrote:

Thanks Steve.
For the next 3 - 4 month it's gonna be a "hot" issue here in Toronto

Even when summer is still 2 weeks away, we're already dealing with +38 C values today (June 10...!!)

You could always share some some of that +38C with us Brits

Duke

avoorpool · **Posted:** Sun Jun 10, 2012 9:03 pm

Duke,

Sure. I might ask the same during the other 8 month a year when e.g we hit windchill values in January of -25 C :lol:

Cheers,

Arthur

GraemeT · **Posted:** Mon Jun 11, 2012 1:30 pm

Arthur,
It's an easy job to add some code to test for the temperature and humidity limits and display humidex only when the conditions are correct for its use.

The php snippet below shows one way to test for and display windchill and heat index. I don't use humidex but it shouldn't pose a problem.
The same can be done using javascript if php isn't an option.

Code:

<?php
if ($temp<="10") 
echo '<td>Windchill</td><td class="obs_data"><span class="ajax" id="wchill"></span></td>';
else if (($temp>"27") && ($dew>"12") && ($hum>"40"))
echo '<td>Heat Index</td><td class="obs_data"><span class="ajax" id="heatindex"></span></td>';
else echo '<td></td><td class="obs_data"></td>';  //pad out with a blank line
?>

avoorpool · **Posted:** Mon Jun 11, 2012 2:03 pm

Thanks Graeme.

Does this work with correct Humidex values, as the Humidex is different from Heat Index since it uses the Dew Point for calculations and of course this varies constantly with the level of Humidity.
Sometimes we see Humidex = Temperature (very low Humidity) but on days like this morning (10:00am Monday June 11) we have a smog advisory in Toronto with a Humidity = 70% / Temp = 23.5 C and Humidex is already 30 C (expected to rise to +36 C this afternoon).
(Also see http://www.csgnetwork.com/canhumidexcalc.html).
It uses the formula: H = T + (0.5555 * (e - 10)), where T is the temperature in Celsius and e is the vapor pressure in millibars (mb), so it depends on several factors to calculate correct Humidex values.
I'll check it out if the figures are correct.

Cheers,

Arthur

gemini06720 · **Posted:** Mon Jun 11, 2012 7:35 pm

Arthur, a while back, I have adapted a PHP function to calculate the humidex factor/temperature using both the temperature and the dew point (and not the humidity) as seen on the Environment Canada's Frequently Asked Questions page - look for the line on "How is the humidex calculated?" (about half way down the page):

The PHP code I came up with is as follow:

Code:

// humidex value calculation - Environment Canada model
function gethumidex ( $temp, $dew ) {
  // FORMULA:
  // humidex = (air temperature in °C) + h
  // where:
  // h = (0.5555)*(e - 10.0);
  // where:
  // e = vapour pressure in hPa (mbar)
  // dewpointK = dewpoint in °C + 273.16 (kelvins)
  // e = 6.11 * exp [5417.7530 * ( (1/273.16) - (1/dewpointK) ) ]
  // ----------------------------------------------------------------------
  $dewpointK = $dew + 273.16;
  $e = 6.11 * exp( 5417.7530 * ((1/273.16) - (1/$dewpointK)) );
  $h = (0.5555)*($e - 10.0);
  $humidex = round(($temp + $h),2);
  return $humidex;
}

GraemeT · **Posted:** Tue Jun 12, 2012 1:31 am

Hi Arthur,
Ray's function will give you resolution to 2 decimal places, whereas the cumulus <#humidex> tag only gives one.
You could selectively show the humidex values using something like this:

Code:

<?php
$humidex = gethumidex($temp, $dew);
echo '<tr>';
if (($temp>"20") && ($dew>"0") && ($humidex>"25")) {
echo '<td>Humidex - Calc</td><td class="obs_data">'.$humidex.'</td>';
echo '<td>Humidex - Cumulus</td><td class="obs_data"><span class="ajax" id="humidex"></span></td>';
}
else echo '<td></td><td class="obs_data"></td>';
echo '</tr>';
}
?>

For clarity I've included lines to show both Cumulus' and the calculated values.
I hope this is useful.

gemini06720 · **Posted:** Tue Jun 12, 2012 5:03 am

Graeme (and Arthur) it is quite easy to change the number of decimals:

Code:

$humidex = round(($temp + $h),2);

will produce a humidex values with two decimals;

Code:

$humidex = round(($temp + $h),1);

will produce a humidex values with one decimal;

Code:

$humidex = round($temp + $h);

will produce a humidex value with no decimal.

Arthur, remember, with PHP, the humidex value is calculated on the hosting server before the page is completely assembled and downloaded to the user's browser's cache.

yv1hx · **Posted:** Wed Jun 13, 2012 3:17 pm

duke wrote:

avoorpool wrote:

Thanks Steve.
For the next 3 - 4 month it's gonna be a "hot" issue here in Toronto

Even when summer is still 2 weeks away, we're already dealing with +38 C values today (June 10...!!)

You could always share some some of that +38C with us Brits

Duke

I can share some of our +42 C ...if anybody tell us how ...

http://met.ivic.gob.ve/red/Cabimas/record.html
http://met.ivic.gob.ve/red/Tarabana/record.html

avoorpool · **Posted:** Tue Jun 19, 2012 1:58 am

Steve,

I noticed in the Today.ini file that the Humidex value is present (however not displayed). the values (Humidex & Time stamp) are incorrect, however is this a w.i.p display

?
We're under a high Humidex Alert (next 4 days +40 - 45 C), so it will be interesting to show these daily high values (better than to "feel" it :lol:

)
(BTW, current values in Cumulus are conform the given calculations by Environment Canada), this in relation to previous messages about this topic.

Thanks,

Arthur

steve · **Posted:** Tue Jun 19, 2012 7:13 am

avoorpool wrote:

hat the Humidex value is present (however not displayed). the values (Humidex & Time stamp) are incorrect,

I've no idea how that got there, Cumulus doesn't write a [Humidex] section to today.ini, it writes a [HeatIndex] section.

avoorpool · **Posted:** Mon Jul 09, 2012 9:32 pm

Hi Steve,

Looking at the weather conditions in W-Europe unfortunately it might not be applicable, however we currently have frequent "Humidex-Alerts" in the Toronto area, issued by Environment Canada. (mostly when it hits close or above +40C)
Is it a simple way to have a [Today] and/or [Month] high and high-time for the Humidex values rather than for the Heatindex??
Thanks,

Arthur.

NOTE: I've changed my webhost for a (paid-for) one, allowing .txt files to be uploaded!!!! (now iPage).
New address: http://www.altonaweather.ca

steve · **Posted:** Mon Jul 09, 2012 9:36 pm

avoorpool wrote:

Is it a simple way to have a [Today] and/or [Month] high and high-time for the Humidex values rather than for the Heatindex??

Sorry, I don't understand the question. Is what a simple way?

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