Topic: Feels Like Temps?

[Mandrake]

A general question if I may.
I have noticed that my HP2551 does not ever seem to show a different 'Feels Like' temp to the actual.
Today we have a lot of humidity due to a continental plume of hot air with humidity sitting at 93% and air temp of 20C as I write but the Feels like temp is the same.
I would have expected this feels like temp to be somewhat higher at these humidity levels.
Is this feature not properly supported or is it actually correct?

My ancient FO/Maplin station that feeds its data into Cumulus MX for instance is saying the feels like temp is 24.5C

Any comments folks?

[galfert]

Heat index Feels Like cannot be calculated if the temperature is less than 26.7 C or 80 F.... and Relative Humidity needs to be higher than 40%.

[Mandrake]

OK, answered my own question....seems that from a meteo perspective Feels like temps only kick above 27C (Heat Index) and below 12C (wind Chill)
I had not realised this and clearly the CumulusMX software is at fault for not aligning I would presume.
I expect to see temps in that range this week so will keep my eye on the console!

[Mapantz]

Heat index Feels Like cannot be calculated if the temperature is less than 26.7 C or 80 F.... and Relative Humidity needs to be higher than 40%.

The 'feels like' temperature here in the UK doesn't work the same as it does in other parts of the world. The MetOffice calculate it for any temperature.

Wind chill, heat index and feels like are all separate entities.

@Mandrake

Cumulus is working correctly. I have wind chill / heat index / feels like on my website. The 'feels like' is higher than the temp/heat index/wind chill, which would be correct.

I think what's happening with the 'feels like' on the Ecowitt station, is that it's actually the wind chill being used but not renaming it to that.

[Mandrake]

Thanks Guys, I was unaware of the UK peculiarity with regards to these values.
I have a peak at @Galferts data in sunny Florida on the ecowitt site and can see he has variable Feels Like values once the temp surpasses 27C.

This all helps reinforce my desire to somehow get the GW-1000 feeding CumulusMX or one of the other Pi based weather software packages in the near future!

[Mapantz]

Thanks Guys, I was unaware of the UK peculiarity with regards to these values.
I have a peak at @Galferts data in sunny Florida on the ecowitt site and can see he has variable Feels Like values once the temp surpasses 27C.

This all helps reinforce my desire to somehow get the GW-1000 feeding CumulusMX or one of the other Pi based weather software packages in the near future!

That's why I am an 'options' type person. I like to see windchill when temps are below 10°C and the wind speed is 3mph or more. Heat index or humidex when the temperature is 27°C or more. If the 'feels like' on the Ecowitt station supported all temps like the MetOffice, it would be better for us here in the UK, but as it's used in different contexts around the world, you can't please everybody.

The only thing I could think of, is to have an individual setting on the dashboard that we can select from a drop down, to either show windchill/humidex/heat index/feels like.

[dunc1ca]

In Canada, UK, and the US, wind chill is all calculated using the same formula.  I couldn't find any reference of a heat index being used in the UK probably because temperatures rarely exceed 30°C in the south and 25°C in the north.

In Canada, we don't use the American formula for heat index.  It's calculated differently and called "humidex".  It's used any time the temperature exceeds 20°C.  The value is generally 5 to 10 degrees higher than the equivalent heat index, although technically the humidex is unitless. 

Example:  temperature: 30°C, dew point 20°C, humidity 55%
In Canada, the humidex is 38. (no unit)
In the US, the heat index is 32°C


Personally, I think the Canadian humidex is overinflated.  The media will report the humidex as though it's an actual temperature too which is misleading.

[Mapantz]

During 'average' temperatures in the UK, the MetOffice use a combination of the heat index and wind chill to formulate a feels like temperature.

[Aussie Susan]

http://www.bom.gov.au/info/thermal_stress/
Near the bottom of the page are the formulae we use in Australia for Apparent Temperature.
Susan

[Felixus]

As Mandrake I also noticed my HP255X keeps the Feels like temperature the same. I was reading few articles about feels like, heat index and wind chill, but decided to use Apparent temperature as best suited in the UK dud to reasons mentioned above. Here's the PHP formula I'm using. It's written by Jachym, the creator of Meteotemplate.

Code: [Select]

// Apparent temperature calculation
    // accepts temperature [C], humidity [%], wind speed [m/s]
    // returns apparent temperature [C]
    function apparent($apparentT,$apparentH,$apparentW){
        $e = ($apparentH/100)*6.105*pow(2.71828, ((17.27*$apparentT)/(237.7+$apparentT)));
        $calcA = round(($apparentT + 0.33*$e-0.7*$apparentW-4),1);
        return $calcA;
    }
I'm displaying all my charts in Cacti as this allows me to calculate and display custom values and can measure things Ecowitt won't such ss battery levels etc.

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[Mandrake]

I tend to use CumulusMx which nicely shows the apparent temps.

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[Felixus]

Looking good. Looks like the apparent temperature is really best suited for the UK weather.  I need to give CumulusMX a try. I saw it runs on Linux, which is great.

[Mandrake]

MX on a Pi and taking data from a GW1000 is a great combo in my opinion.

I do plan to try WeeWx at some point when I find time.