<p>Everything.</p>

<ul>
<li>Parametrizations</li>
<li>Spatial (horizontal and vertical) and temporal resolution</li>
<li>Initialization</li>
<li>Dynamical core</li>
<li>Handling of some complex non-linear physical processes (i.e. snow)</li>
<li>Topography representation</li>
<li>How the mathematical equations are numerically implemented</li>
<li>The computer used</li>
<li>etc...</li>
</ul>

<p>These are some of the main differences between 2 given numerical weather model. </p>

<p>With that being said, the same model will give different results when run on a different computer (Hong et al. 2013).</p>

<p>Hong S-Y, Koo M-S, Jang J, et al. (2013) An Evaluation of the Software System Dependency of a Global Atmospheric Model. Mon Weather Rev 141:4165–4172. doi: 10.1175/MWR-D-12-00352.1</p>

CC BY-SA 3.0
2014-08-08T17:17:34.310Z
2014-08-08T17:17:34.310Z
Balinus
<p>A difference of accuracy between weather models can be due to different factors, one of these is certainly the availability of "good" initialization data. As pointed out in Bradley Ballish (NOAA/NCEP) in his <a href="http://www.emc.ncep.noaa.gov/gmb/wd23ja/presentations/dropout/AMS%20Oral%20Presentation%20Ballish.ppt">AMS presentation</a> the accuracy of GFS has improved drastically when ECMWf initaliziation data have been used. Furthermore, I think there is a big difference in computational power between the two centers, ECMWF center has bigger and faster supercomputers.  </p>

CC BY-SA 3.0
2017-10-22T12:37:05.283Z
a faster supercomputer can allow  a more detailed (in spatial resolution, temporal resolution) and, in principle, more realistic modelisation.
Matteo De Felice
CC BY-SA 3.0
2014-05-13T11:59:09.073Z
2014-05-13T11:59:09.073Z
Matteo De Felice
<p>It's often said that the ECMWF model is more accurate than the GFS. But what are the reasons why? Also, how does the NAM compare with these two and other forecasting models?</p>

CC BY-SA 3.0
2014-05-13T19:32:31.243Z
That's two different questions: (1) are there significant differences between different weather models' accuracy, and (2) if yes, why?.  Who claims that ECMWF is more accurate than GFS?
gerrit
CC BY-SA 3.0
2014-05-13T22:38:13.233Z
@gerrit I don't think there's need for two questions, but I agree, this question should be revised to include some of many examples where ECMWF demonstrated higher skill than GFS.
milancurcic
CC BY-SA 3.0
2014-07-02T10:40:14.163Z
"It's often said" are [weasel words](https://en.wikipedia.org/wiki/Wikipedia:Weasel_word#Unsupported_attributions). I think we should avoid them here as they try to at wikipedia.
naught101
<meteorology><weather><models><nwp>
What determines the differences in results between various weather models?
InquilineKea
# What determines the differences in results between various weather models?

(Asked by: username_0 on 2014-05-11)

It's often said that the ECMWF model is more accurate than the GFS. But what are the reasons why? Also, how does the NAM compare with these two and other forecasting models?

**Tags:** meteorology, weather, models, nwp

> **Comments:**
> **username_1**: That's two different questions: (1) are there significant differences between different weather models' accuracy, and (2) if yes, why?.  Who claims that ECMWF is more accurate than GFS?  
> **username_2**: @username_1 I don't think there's need for two questions, but I agree, this question should be revised to include some of many examples where ECMWF demonstrated higher skill than GFS.  
> **username_3**: "It's often said" are [weasel words](https://en.wikipedia.org/wiki/Wikipedia:Weasel_word#Unsupported_attributions). I think we should avoid them here as they try to at wikipedia.  

---

## 2 answers

### Answer by username_4 on 2014-08-08. Score: 9

Everything.

* Parametrizations
* Spatial (horizontal and vertical) and temporal resolution
* Initialization
* Dynamical core
* Handling of some complex non-linear physical processes (i.e. snow)
* Topography representation
* How the mathematical equations are numerically implemented
* The computer used
* etc...

These are some of the main differences between 2 given numerical weather model.

With that being said, the same model will give different results when run on a different computer (Hong et al. 2013).

Hong S-Y, Koo M-S, Jang J, et al. (2013) An Evaluation of the Software System Dependency of a Global Atmospheric Model. Mon Weather Rev 141:4165–4172. doi: 10.1175/MWR-D-12-00352.1


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### Answer by username_5 on 2014-05-13. Score: 6

A difference of accuracy between weather models can be due to different factors, one of these is certainly the availability of "good" initialization data. As pointed out in Bradley Ballish (NOAA/NCEP) in his [AMS presentation](http://www.emc.ncep.noaa.gov/gmb/wd23ja/presentations/dropout/AMS%20Oral%20Presentation%20Ballish.ppt) the accuracy of GFS has improved drastically when ECMWf initaliziation data have been used. Furthermore, I think there is a big difference in computational power between the two centers, ECMWF center has bigger and faster supercomputers.

> **Comments:**
> **username_5**: a faster supercomputer can allow  a more detailed (in spatial resolution, temporal resolution) and, in principle, more realistic modelisation.  

---

