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Winter Banter Thread


Rjay
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6 hours ago, donsutherland1 said:

Which is right? Note the difference isn't in the use of Fahrenheit vs. Celsius. The difference is in whether the anomalies are warm or cold in parts of the Southeast. The upcoming weeklies for the March 6-13 period will probably offer a hint of where the European guidance is leaning.

Tropical Tidbits:

image.thumb.png.de73f86cce2b1ca092a6c54a8f26b55e.png

WeatherBell:

image.thumb.png.0586768110a3fd5fe47f076adf3ad1b3.png

 

 

Don,

 I earlier ITT said I was concerned about WxBell anomalies often having too large extremes and thus not trusting their anomaly maps. However, I decided to try to answer your question based on an objective analysis:

 1. I decided to focus on Athens, GA, because you're focusing on the SE, the 360 hour forecast map I posted below shows them at ~55 F at 7 PM EST on 3/9/23, there's a large discrepancy there in the anomalies between WxBell and TT, and there's easy to find history for Athens.

2. WxBell (using 1991-2020 as a base) has them 4 F BN, implying a 59 F norm for 7 PM on March 9th for the period 1991-2020.

3. Tidbits (using 1981-2010 as a base) has them ~1.75 C AN or ~3 F AN, implying a 52 F norm for 7 PM on March 9th for the period 1981-2010.

4. So, I next needed to find Athens' average 7 PM March 9th temperature for both 1991-2020 and 1981-2010. 

5. I found a great site with hourlies for any date going back to 1981. This link is for 3/9/1981. Just click on 7 PM on the top chart and then change the year to get the same for 1982-2020:

https://www.wunderground.com/history/daily/us/ga/athens/KAHN/date/1981-3-9

6. Based on the data from this site, the 1991-2020 avg for 7PM on March 9th at Athens is 57 F. WxBell implied it was up at 59. Thus, WxBell's Athens normal for 7PM that day is 2 F too warm, which means that WxBell's 4 F BN should have instead been 2 F BN.

7. Based on the data from this site, the 1981-2010 avg for 7PM on March 9th at Athens is 56 F. TT implied it was only 52. Thus, TT's Athens normal for 7 PM that day is 4 F too cold, which means that TT's 3 F AN should have instead been 1 F BN or ~0.5 C BN.

8. Conclusion: The 7 F discrepancy between the WxBell and TT maps regarding the 7 PM March 9th normal at Athens (as representation for the SE) was due to a combination of them using different base periods (1 F), WxBell using a normal that is 2 F too warm, and TT using a normal that is 4 F too cold. So, although all three are factors, TT (4 F) was surprisingly the biggest factor rather than WxBell (2 F) or the different base periods (1 F). Without doing this, I would have guessed that WxBell was the biggest factor based on my prior impression about them.

----------------------------

This 0Z 2/23/23 run's 360 hour EPS mean map has Athens at ~55 F:

52D707E5-176E-4033-8BFB-95854D6485F4.thumb.png.c6cad9988034b40f1c071f6ff8f16304.png

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6 hours ago, IrishRob17 said:

Interesting. Lets throw another into the mix:

Capture 2-23-23.JPG

 Piggybacking off of my reply to Don's question that I focused on Athens, GA, for my answer:

 This Weathermodels map has Athens at ~1/2 C BN or ~1 F BN as of 7 PM on March 9th. The TT EPS mean map had Athens at ~55 F then. It says on your map that Weathermodels uses 20 years for climate. Now consider this for Athens using this great site:

https://www.wunderground.com/history/daily/us/ga/athens/KAHN/date/1981-3-9


2001-2020 avg for 7PM: 59 F

2003-2022 avg for 7PM: 59 F

 So, 55 F - 59 F = -4 F. 
 
 Thus, for Athens as a representative for the SE, the anomaly on their map of ~-1 F should have been more like -4 F if we assume they're using either 2001-2020 or 2003-2022 for climo.

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16 minutes ago, GaWx said:

 Piggybacking off of my reply to Don's question that I focused on Athens, GA, for my answer:

 This Weathermodels map has Athens at ~1/2 C BN or ~1 F BN as of 7 PM on March 9th. The TT EPS mean map had Athens at ~55 F then. It says on your map that Weathermodels uses 20 years for climate. Now consider this for Athens using this great site:

https://www.wunderground.com/history/daily/us/ga/athens/KAHN/date/1981-3-9


2001-2020 avg for 7PM: 59 F

2003-2022 avg for 7PM: 59 F

 So, 55 F - 59 F = -4 F. 
 
 Thus, for Athens as a representative for the SE, the anomaly on their map of ~-1 F should have been more like -4 F if we assume they're using either 2001-2020 or 2003-2022 for climo.

Thank you, GaWx. Tropical Tidbits needs to update its baseline, in this case. The 1981-2010 baseline is no longer being used. So, at present, the issues that exist with the maps that I'm now aware of are:

1. TT uses an incorrect baseline on its maps where anomalies are shown (its snow algorithm continues to treat sleet and freezing rain as snow in the 10:1 totals)

2. WxBell uses the CFSv2 as an operational model rather than averaging over multiple runs

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12 hours ago, TWCCraig said:

The difference is probably resulting from using different climate averages. Tropical tidbits looks to be using CFSR 1981-2010, Weatherbell is using ECMWF ERA-5 1991-2020. Weathermodels.com appears to be using some 20-year average. The differences could also be resulting from whether it's a instantaneous snapshot of temperature anomalies, or the average of the anomalies over the past 6 to 12 hours

why use climate averages at all? this to me is an example of pseudoscience.  who decided that 30 year averages should be used?  that's a subjective decision-- I'd much rather they show the actual temperatures not some proclaimed climate "average"

 

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5 minutes ago, North and West said:

When we see coastal California getting snow and NWS San Diego issuing blizzard warnings

https://www.instagram.com/reel/CnF5ZKfPHww/


.

Those mountains are pretty high, there are probably places there that average more snow than we do.

Elevation usually trumps latitude.

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19 hours ago, LibertyBell said:

why use climate averages at all? this to me is an example of pseudoscience.  who decided that 30 year averages should be used?  that's a subjective decision-- I'd much rather they show the actual temperatures not some proclaimed climate "average"

 

In this case it makes a lot of sense. You want to build your current models around what your current date averages are and they continue to increase over the last 60 years. Today’s set up would not yield the same result that 30 years ago did. 

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6 hours ago, CPcantmeasuresnow said:

In this case it makes a lot of sense. You want to build your current models around what your current date averages are and they continue to increase over the last 60 years. Today’s set up would not yield the same result that 30 years ago did. 

That's different but in that case why 30 years when 10 years would be more accurate, or even better use a weighed average that emphasizes the last 10 over the 20 years before that.

 

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