Author Topic: Daily Average Temperatures  (Read 1241 times)

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Offline WeatherHost

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Daily Average Temperatures
« on: March 28, 2018, 05:33:22 AM »
They really need to do that differently.

We were between 56 and 58 almost all day yesterday.  Only 5 of the hourly observations recorded were 60 or above.  One was recorded at 70 and the official high was recorded at 71 which apparently was only for a few minutes since the next hour dropped back to 59.  Yet the official high and low were 71 and 55 for an average of 63 or 11 above normal.  One of the hourly observations was 63 and only 4 out of 24 were above that.

Also, I never saw above 65 on my console, about 40 air miles from the NWS Office.  The front stalled between us.

By all common sense, our average daily temperature was more like 57 or 58.

This is a big part of how 'normals' are getting skewed over time.

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Offline WeatherHost

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Re: Daily Average Temperatures
« Reply #1 on: March 28, 2018, 05:42:35 AM »
The 24 hourly observations total 1425, then divided by 24 equals 59.38

That's still above the 'normal' for the day which is 52, but only 7 degrees, not 11.





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Offline spc fresno

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Re: Daily Average Temperatures
« Reply #2 on: May 29, 2018, 02:14:29 PM »
Maybe they should use the Median Temperature, rather than the mean. I agree, that if that particular date has an outlier, it shouldn't have such a large effect on the total day average. The median would make it so that if a given temperature range dominated during the 24 hours, it would likely be towards the middle of all the numbers, lined up lowest to highest.

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Offline SupaWX

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Re: Daily Average Temperatures
« Reply #3 on: June 01, 2018, 06:24:36 PM »
I used to calculate the daily mean and median, but 99% of the time they were within a degree of each other so I stopped doing the median.
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Offline WeatherHost

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Re: Daily Average Temperatures
« Reply #4 on: September 04, 2018, 03:22:47 AM »
This has been happening quite a bit lately.  I can only surmise that the 6 hour highs happened for a few minutes between the hours, but I have to wonder ho much it's skewing the averages.


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Offline Mattk

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Re: Daily Average Temperatures
« Reply #5 on: September 04, 2018, 05:08:55 AM »
Well that's one way to increase (manipulate) maximum temperatures to justify, you know what.

Offline ValentineWeather

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Re: Daily Average Temperatures
« Reply #6 on: September 04, 2018, 05:37:42 AM »
I see it all the time where airport ASOS high never shows on the supposedly 5 minute average temperature but somehow magically appears on summary as high for day. Then I've seen the lowest lows get skipped doing the same thing. These are running averages and if it shows up as a 5 minute average low how does it get skipped? Happens all the time.
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Offline Mattk

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Re: Daily Average Temperatures
« Reply #7 on: September 04, 2018, 07:21:39 AM »
Well the lowest lows get skipped to inflate the maximum temperature trend, this is a well known ploy by agencies attempting to justify .. you know what! I believe NOAA started this fiddling the lower end of the temperatures as well as the maximums to increase the perception and a few other countries picked up on this ploy with fiddling the bottom end, quite a sneaky lot is this mob trying to justify ... you know what.
« Last Edit: September 04, 2018, 07:24:19 AM by Mattk »

Offline WeatherHost

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Re: Daily Average Temperatures
« Reply #8 on: September 04, 2018, 10:22:23 PM »
And again ....

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If we put a red & white stocking cap on it, we could play 'Where's 96' !!

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Offline ValentineWeather

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Re: Daily Average Temperatures
« Reply #9 on: September 05, 2018, 01:40:41 AM »
You need to turn on the 5 minute updates. What airport is this?
If you don't know how to turn on use mesowest they have it on automatically.
Still with 5 minute updates on I've see same thing happen on both low and high side.
Randy

Offline WeatherHost

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Re: Daily Average Temperatures
« Reply #10 on: September 05, 2018, 02:26:58 AM »
You need to turn on the 5 minute updates. What airport is this?

The official NWS KPAH site.  No settings on my end to alter.

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Offline ValentineWeather

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Randy

Offline ValentineWeather

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Re: Daily Average Temperatures
« Reply #12 on: September 06, 2018, 08:40:14 AM »
Here is a good example today where the 5 minute average was lower than reported.  So this goes down as full degree warmer than actual.
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Randy

Online CW7491

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Re: Daily Average Temperatures
« Reply #13 on: September 06, 2018, 11:25:01 AM »
What Iíve noticed about ASOS is aside from hourly and special observations (which are reported as the actual temperature in deg F or rounded to the nearest deg F), the 5 min observations are rounded to the nearest deg C and converted to deg F. This brings in rounding error on the Fahrenheit scale. For example, if ASOS is actually reading 10.5C, it converts to 50.9F. The problem is the 5 min ASOS report will round 10.5C to 11C and that converts to 51.8F. So it can make temperature look artificially high or low depending on the rounding, but never more than 1degF. What Iíve also noticed is despite this, ASOS will report the correct max of 51F not the incorrect 52F even when the 5 min obs was reported as 52! If you convert the 5 min ASOS obs from F to C, youíll notice it always converts to the whole deg C. So you have to be careful with the temp comparisons using 5 min obs from ASOS.

In the example above, 48.2F is 9C. 50.0F is 10C. The actual temp was probably bouncing between 9.4C and 9.5C, but it shows up as a 2degF swing. The hourly obs at 6:52 of 48.9F is the actual temp in degF which converts to 9.4C and that is what is reported as the min instead of the rounded (and erroneous) 48.2F.
« Last Edit: September 06, 2018, 11:55:43 AM by CW7491 »

Offline ValentineWeather

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Re: Daily Average Temperatures
« Reply #14 on: September 06, 2018, 12:01:03 PM »
Interesting, I asked the local FSO and they were not sure why it does this. Actual said it was the first time someone brought it up...lol
Randy

Offline ValentineWeather

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Re: Daily Average Temperatures
« Reply #15 on: September 06, 2018, 12:06:53 PM »
Here it is in metric.
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Randy