Heat index bug

Discussion in 'Weather Watcher - Help' started by dlbryant, Jul 3, 2013.

  1. dlbryant

    dlbryant Well-Known Member

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    I was looking at Bakersfield, CA and it was 109F, 11% humidity, and a heat index of 109F (according to Weather Watcher).

    The heat index should be 104F. This according to the National Weather Service.

    In dry and hot like southern California and Arizona and in other Southwest states, the heat index might be lower than the actual temperature. Weather Watcher does not recognize such cases and just make the heat index the same as the actual temperature.

    Please fix this!

    David
     
  2. msinger

    msinger Administrator
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    I don't believe Weather Watcher Live is setting the heat index to the current temperature. It looks like there are two issues:

    1) When the temperature and/or dew point update in real time in the main window, the humidex is not being updated.

    2) Also, it looks like there is a possible error in the humidex calculation I'm using.
     
  3. dlbryant

    dlbryant Well-Known Member

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    The current conditions according to the NWS:

    Actual 110F
    Humidity 11%
    Dew 43F
    Heat Index 105F

    WW Live says 110F heat index.
    This is from Bakersfield Airport (Weather Underground Meadows Field station)
    The WeatherBug airport site is correct.


    David
     
  4. msinger

    msinger Administrator
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    I reviewed the humidex calculation in Weather Watcher Live and it looks correct. The sample numbers I ran through it provided the expected results too. I'm using this formula:

    http://en.wikipedia.org/wiki/Humidex

    The "Heat Index" shown at WeatherUnderground.com is the "Feels Like" temperature shown in Weather Watcher Live. Heat index is not the same thing as humidex though. There are different calculations for both.

    http://en.wikipedia.org/wiki/Heat_index
     
  5. dlbryant

    dlbryant Well-Known Member

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    I'm talking about the Feels Like at Meadows Field at Bakersfield. The Weather Underground station there had a feels like the same as the actual temperature. However, WeatherBug is correct at the same station, below the actual temperature. The NWS website confirmed this.

    While we are talking about WeatherBug, they forecast lows in the high 90's for several days. This is obviously an error.
     
  6. msinger

    msinger Administrator
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    Currently, I don't see anything odd about the weather data. There is a difference in the current conditions. That makes sense though since the data was last updated at different times.

    [​IMG]
     
  7. msinger

    msinger Administrator
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    The Weather Watcher Live build below should resolve the hourly issue. For the next couple of days, I pull the highs/lows from the hourly forecast and display them in the daily forecast -- since the hourly forecast is usually more accurate. The lows were in the morning hours for your area, but Weather Watcher Live was only looking up until midnight. I modified that process so it looks as far as 5 AM the next morning for the lowest temperature.

    https://www.box.com/s/eqet6nxuorpu1e3a77ir
     
  8. dlbryant

    dlbryant Well-Known Member

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    I ran some numbers through a couple of online heat index calcuators, and when the heat index is higher than the actual temperature, the heat index is correct.

    However if the heat index is below the actual temperature, the Weather Underground stations are off by 2-3 degrees.

    Please take a look at this matter.

    David
     
  9. msinger

    msinger Administrator
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    I think the issue is that I'm not following what you're describing. Can you post some screenshots to show what you're looking at?
     
  10. dlbryant

    dlbryant Well-Known Member

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    Here's an example:

    In Palm Springs, CA it was 113F with a Dew Point of 45F.

    According to the Heat Index Formula, it should be 108F.
    According to Weather Watcher Live, the heat index is 113F.

    There's something wrong with WWL calculating Heat Index when the Heat Index is lower than the actual temperature.

    Thanks for your patience, Mike.

    David
     
  11. msinger

    msinger Administrator
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  12. dlbryant

    dlbryant Well-Known Member

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    I took the temperature, humidity, and dew point from stations on WW Live and recalculated the numbers at a National Weather Service weather calculator. and compared their results with WW Live.

    Here's the site:

    http://www.srh.noaa.gov/tsa/?n=met_calc

    David
     
  13. msinger

    msinger Administrator
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    Please post a screenshot showing the incorrect heat index in WWL.
     
  14. dlbryant

    dlbryant Well-Known Member

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    [​IMG]



    [​IMG]


    The heat index should be 107F
     
  15. dlbryant

    dlbryant Well-Known Member

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    Strange that this happened just now...I've seen other places that have done the same thing. Inconsistent feel-like readings.

    Actually the heat index in Palm Springs is 107.5F


    [​IMG]
     
  16. msinger

    msinger Administrator
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    Here's what I'm seeing:
    [​IMG]
     
  17. dlbryant

    dlbryant Well-Known Member

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    It looks like an Weather Underground problem, not WW Live problem. The heat index formula says it should be 107.0F, not 111F.

    I don't know how Weather Underground calculates the Feels Like temp. It's not the same as that of the NWS. I'll have to e-mail Tech Support,
    though I don't think it would change anything.

    I installed Windows 8 on my system last night (it installed and runs flawlessly), and they have an AccuWeather app. Pretty cool one at that. They have a
    totally different way to determine the Feels Like temp and more true to the actual true to the weather condition.

    Did you ever try to use AccuWX's data feed for the late and great Weather Watcher (not-so-live)?

    David