Review of Ribberink et al. (2025) 

Summary: This study examines changes in Ophelia’s structure, behavior, and impacts between current and idealized future climate scenarios, particularly focusing on its extratropical transition. Simulations using a regional model show that in warmer scenarios, Ophelia becomes stronger, larger, and shifts its path westward, delaying its extratropical transition and maintaining more tropical characteristics, leading to increased impacts at landfall. The study also highlights that the storm's intensity and impact are sensitive to initial conditions, and the tropical phase is more affected by temperature changes than the extratropical phase, emphasizing the importance of accurate tropical cyclone modeling for predicting post-tropical cyclone impacts. 

Overall assessment: In general, I find this study both interesting and valuable to the scientific community. It provides insights into the response of post-tropical cyclones to a warmer climate and their potential impacts on regions like Western Europe. Additionally, the study explores the physical mechanisms behind changes in the storm's structure, behavior, and impact in response to various warming and cooling scenarios. However, I do have some concerns and/or required clarifications. These are highlighted in subsection below. I suggest publishable with major revisions, since I believe the authors need to make some rather substantial text modifications and additions to fine-tune the message of this study. I think the manuscript will be publishable after some more work. 

Major comments: 

1) Introduction: The introduction is generally well-written, providing the background and motivation for this study. However, the specific research question or hypothesis could be clearer. For example, explicitly stating what the paper aims to address or how it intends to fill a gap in the current literature would strengthen the introduction further. Additionally, details about the chosen case could be moved to later sections (e.g., Section 3.1; this section is too short), allowing the introduction to remain focused and concise, while the authors briefly mention it. Aside from the introduction, the following sections are quite similar, with only a few lines presented in each. 

2) Introduction: It would be helpful to include a brief outline of the paper, as this can guide the reader and give them an idea of what to expect in each section. 

3) Section 2: This section contains numerous subsections, many of which are only a few lines long. Please consider consolidating these subsections to make the content more concise. For example, sections 2.6.1 and 2.6.2 can be combined. 

4) Lines 220-222: If this is the case, I think the large deficit in MSLP (e.g., 912 hPa) should not be captured in these simulations either. There seems to be misrepresentations somewhere in the dynamical processes that prevent the storm from achieving the gradient wind balance. Additionally, if the authors used instantaneous maximum wind speeds recorded at specific time intervals (e.g., hourly output data; please also specify the frequency of output from your simulations), they might have missed the actual maximum wind speed that occurred between these intervals. On the other hand, as the authors described, IBTrACS provides 1-min average maximum sustained wind speed. 

5) Lines 223-225: After October 16, it is possible that all the simulated storms begin interacting with land, which could significantly influence wind speed. Although the +2~+4 storms are located further west compared to the cooler ones, their larger storm radius suggests they may begin interacting with land. Line 243 may support this speculation. Please consider adding information about the size of the simulated storms for clarification. 

6) Lines 293-295: Do the authors have any insights on why warmer storms remain symmetric for longer? The parameter B, determining the onset of ET, basically represents the difference in atmospheric thickness between the left and right sides of the storm, and since all the experiments are conducted under uniformly warmed or cooled conditions, there shouldn't be any temperature gradient differences among them. Additionally, it seems there are no noticeable differences in their locations at the onsets. 

7) Lines 345-346: I think this statement is true depending on cases. Typically, TCs undergoing extratropical transition experience an expansion of their wind field, with the radius of maximum winds increasing and the overall wind structure becoming broader and more asymmetric. Additionally, as these storms interact with upper-level waves, their translational speed often accelerates significantly, similar to that of extratropical cyclones. Please consider revising or rephrasing this discussion. 

8) Figure A1: Do the five different initialization times lead to significant differences in storm size? For the simulations initialized on 14 and 15 Oct, no significant differences are seen in tracks. As discussed in the main manuscript, all the storms in these sets of simulations have similar storm size, so they are less affected by the beta drift? If the warmer storms become larger, does the hypothesis that beta drift drives the westward shift of the warmer storms still hold? Beta drift should become more pronounced at higher latitudes. 

9) Beta drift: It appears that the calculated beta drift among the simulations converges to values within 0.3 m/s after 15th Oct., while the jet streams on 16th show a more diverse distribution (Fig. B2). Could this variation in jet stream distribution be driving the track divergence, rather than the beta drift? Related to this question, Lines 253-256: However, during this period, the warmer storms do not show a noticeable westward shift in their tracks. The significant divergence becomes apparent after the 15th, when the beta drift converges. 

Minor specific points: 

1) Line 80: Please complete the sentence. 

2) Lines 106-109: Consider rephrasing these lines. 

3) Figure B1: The IFS is not represented in this figure. Are the solid lines derived from GFS forcing data? Please clarify the figure caption. 

4) Figure 3: Please add the storm's daily locations to the inset figure. 

5) Line 204: This study does not use the PGW approach. Need to be rephrased. 

6) Figure 4(c): Please clarify this figure. It seems the authors are trying to show storm size based on the 17 m/s threshold. What exactly does the y-axis value represent? Is it latitudinal distance, and if so, relative to what? The storm centers? 

7) Line 249: Please consider providing the formulation applied in this study so that readers can better understand the environmental factors contributing to the shift in the simulated storms. 

8) Lines 345-346 and others: What does Bft mean?