Overview

The authors here present an interesting study where they examine variability and relationships between numerous measures of intensity of extratropical cyclones in the North Atlantic in ERA5. This is a very comprehensive study and methodical in nature and presents very interesting results. The main results of interest are on the clusters of storms, their different geographic locations and also different populations in the wider intensity distributions. Due to the methodical nature of this study, it clearly presents very worthwhile findings, my only criticism of this work is that the study is incredibly long and in some places perhaps overly so. I understand why this is as the authors have conducted a lot of analysis, however in places brevity may be an option. I have other minor comments, which i have detailed below, and once these have been addressed i think this study will be an excellent addition to this journal.

Minor comments

1. L37/38 "However, in many cases, neither the minimum MSLP nor maximum VO correlates well with the impacts of a given ETC" needs a reference
2. L52 - specify that you are referring to "average strength" cyclones
3. L88 - typo in the statement of spectral resolution
4. Section 2.2 - do you also perform the tracking using 3-hourly resolution, or use the standard 6-hourly approach? Please specify in this section
5. L111 - I assume you are using VO at 850 hPa for tracking, but you do not state this initially, this needs to be done
6. L161 - your baseline intensity measure is VO from the tracks. If this is the case you need to state that this is the T42 filtered vorticity, and not vorticity that you would get directly out of ERA5. Anyone trying to re-produce your results would have to do the tracking in order to get this variable
7. L245 - i believe there is a brackets issue in this line
8. Section 4.3 - all sections here are very long and descriptive and i feel is an area where some text can be removed and sections shortened for the benefit of future readers.
9. L500-511 - you state for this paragrpah that the results of Fig 9 are the same as Fig 8, which is what you would expect as it is just the same data but presented in a different manner. If this paragraph (and Fig. 9) are not essential for your results i would consider removing.
10. Figure 10 - it would be good to state the trend value (and associated uncertainty) in each panel and the associated places in the text. Also, how much are your trends associated with modes of variability such as the NAO?