This study examined the dynamics leading to the RI event of Hurricane Lidia by examining the ensemble forecasts produced by the IFS-EPS. This paper is overall well written, and the analyses are robust and detailed, showing a convincing difference between members that underwent RI versus members that slowly intensified. I only have some minor suggestions and clarification questions that would require the attention of the authors. Therefore, I recommend a minor revision before publication.

Minor comments:

L212: To evaluate the role of … This sentence is grammatically incorrect.

Fig. 1: I would suggest overlaying the observed track of Lidia in Fig. 1a. For Fig. 1b, why not overlay the observed MSLP directly over the simulated time series, instead of showing them in a subplot at the bottom right? Overlaying it directly would help readers see that the P80 member is clearly capturing a realistic RI event.

L297-298: What about the other members shown in gray-dashed lines in Fig. 1a? Many of them are even further north, which should have an even closer proximity to the trough. Why are these members not intensifying as quickly as the P80 group? I am not asking the authors to do more analysis here, but it is quite puzzling to me, and I think some clarification here would be helpful.

Regarding L295-306, L493-502: I would suggest adding a figure or a panel showing the relative position of the trough and the TC (perhaps using the reanalysis) near the discussion of L295-306. This paragraph (L295-306) is the best place to show this information, as it allows the readers to have a clear sense of the potential importance of the trough to the RI event. Also, I found the placement of L493-502 a bit odd. I think the discussion of L493-502 is more related to the discussion in L295-306. So, overall, I would suggest merging the discussion of L493-502 with L295-306 and adding a panel (or figure) to show the TC-trough relative position clearly early on.

The discussion about PI in L316-330: I am totally convinced that PI is not the limiting factor of the RI of this event, especially given that this case is clearly externally forced by the approaching trough. However, for TCs without interaction with the external environment or features, the TC would inevitably undergo RI when the environmental condition is favorable (e.g., with high PI, for example, all the idealized TC simulations in previous studies did not need external forcing and features for it to undergo RI). In those cases, having sufficiently high PI is enough to guarantee the occurrence of RI, even though the details of RI, such as the onset timing and triggering, are sensitive to the detailed vortex structure, humidity distribution at the TC inner core and boundary layer, etc. I would suggest the authors limit their discussion to this specific case, such as in L317-318, 322.

L358: Maybe also say broader and deeper? 200-hpa shows a very small difference, while 300 and 500 hpa are much clearer, so maybe mention which level you are referring to.

L362: What is a ventilation layer? Please define it clearly. I also found that the authors have a misinterpretation of what ventilation means. It would seem to me that the authors are referring to divergence. See my later comments for more details.

L516: Need to define V_irr? Does it mean an irrotational wind vector?

Ventilation: In TC dynamics, ventilation processes specifically refer to the injection of low-theta-e air from the TC environment to the TC inner core and eyewall convection, which would suppress the eyewall convection and intensification of TC (Tang and Emanuel 2010, 2012). There are major pathways of ventilation, including radial ventilation and downdraft ventilation (Alland et al. 2021a,b). It would seem to me that the authors are not referring to these ventilation processes. If so, please change the ventilation terminology to something else, since the current meaning and context of ventilation used here are quite contradictory to the conventional definition of ventilation (I believe that the authors think ventilation is beneficial to TC intensification).

Reference:

Tang, B., and K. Emanuel, 2010: Midlevel Ventilation’s Constraint on Tropical Cyclone Intensity. J. Atmos. Sci., 67, 1817–1830, https://doi.org/10.1175/2010JAS3318.1.

Tang, B., and K. Emanuel, 2012: A Ventilation Index for Tropical Cyclones. Bull. Amer. Meteor. Soc., 93, 1901–1912, https://doi.org/10.1175/BAMS-D-11-00165.1.

Alland, J. J., B. H. Tang, K. L. Corbosiero, and G. H. Bryan, 2021a: Combined Effects of Midlevel Dry Air and Vertical Wind Shear on Tropical Cyclone Development. Part I: Downdraft Ventilation. J. Atmos. Sci., 78, 763–782, https://doi.org/10.1175/JAS-D-20-0054.1.

Alland, J. J., B. H. Tang, K. L. Corbosiero, and G. H. Bryan, 2021b: Combined Effects of Midlevel Dry Air and Vertical Wind Shear on Tropical Cyclone Development. Part II: Radial Ventilation. J. Atmos. Sci., 78, 783–796, https://doi.org/10.1175/JAS-D-20-0055.1.