The role of large-scale dynamics in an exceptional sequence of severe thunderstorms in Europe May–June 2018

Mohr, Susanna; Wilhelm, Jannik; Wandel, Jan; Kunz, Michael; Portmann, Raphael; Punge, Heinz Jürgen; Schmidberger, Manuel; Quinting, Julian F.; Grams, Christian M.

doi:https://doi.org/10.5194/wcd-1-325-2020

Articles | Volume 1, issue 2

https://doi.org/10.5194/wcd-1-325-2020

© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

https://doi.org/10.5194/wcd-1-325-2020

© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 1, issue 2

Research article

|

17 Jul 2020

Research article |

| 17 Jul 2020

The role of large-scale dynamics in an exceptional sequence of severe thunderstorms in Europe May–June 2018

Susanna Mohr, Jannik Wilhelm, Jan Wandel, Michael Kunz, Raphael Portmann, Heinz Jürgen Punge, Manuel Schmidberger, Julian F. Quinting, and Christian M. Grams

Download

Final revised paper (published on 17 Jul 2020)
Supplement to the final revised paper
Preprint (discussion started on 14 Jan 2020)

Interactive discussion

Status: closed

AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment

- Printer-friendly version

- Supplement

RC1: 'Review for WCD-2020-1', Anonymous Referee #1, 11 Feb 2020
- AC1: 'Reply to Anonymous Referee #1 (RC1)', Susanna Mohr, 25 Mar 2020
RC2: 'Review criteria/main comments/specific comments', Anonymous Referee #2, 23 Feb 2020
- AC2: 'Reply to Anonymous Referee #2 (RC2)', Susanna Mohr, 25 Mar 2020

Peer-review completion

AR: Author's response | RR: Referee report | ED: Editor decision

AR by Susanna Mohr on behalf of the Authors (22 Apr 2020) Author's response Manuscript

ED: Publish subject to revisions (further review by editor and referees) (06 May 2020) by Martin Singh

ED: Referee Nomination & Report Request started (16 May 2020) by Martin Singh

RR by Anonymous Referee #1 (01 Jun 2020)

RR by Anonymous Referee #2 (05 Jun 2020)

For final publication, the manuscript should be

accepted as is

accepted subject to technical corrections

accepted subject to minor revisions

reconsidered after major revisions

I would be willing to review the revised paper, if the editor considers it necessary.

I am not willing to review the revised paper.

rejected

Suggestions for revision or reasons for rejection

The paper describes an extraordinary thunderstorm episode of western and central Europe in May/June 2018. The situation was related to an unusually high cut-off low activity at the upstream side of a quasi-stationary blocking. The authors use multiple data sets to study the situation. The paper improved highly from the first version: It is now an easy, nice read. The paper has a very good, easy-to-follow structure. An additional trajectory analysis gives insight to the quasi-stationarity of the situation. An interesting outcome is the potential linkage between large-scale weather patterns (European weather regimes) and thunderstorm activity which should be studied in more detail in the future.

Abstract: I like the abstract. I think an additional last sentence would be nice that describes the benefits and aim of the paper. Something like you write in line 76-80 in your introduction:
"The primary objective of this paper is to examine the conditions and processes that made this particular thunderstorm episode in 2018 unique. We focus on the process interaction across scales, i.e., from the large-scale dynamics such as atmospheric blocking to meso-scale PV cut-off lows and/or small meso-scale PV filaments to modifications of the convective environment to local-scale thunderstorm occurrences. Further objectives are to highlight the synoptic setting during the thunderstorm episode, to demonstrate the severity of the events, and to place the event in a historical context."

More specific comments:

2. Data and Method: This section improved really much. It is now very clear what kind of data you use for what purpose. And it gives a clear an concise overview. Thanks for taking into account the reviewer's comments!

Section 3.1.1: I like the connection the authors made between regime changes and convective activity. This would be interesting for a future climatology!

Section 3.1.2: Thanks for adding a comparison with bulk wind shear. The comparison nicely shows that V500 is almost identical to BWS over land in this situation. Overall the unusual situation seems to be clearer discussed (or plotted)

Section 3.2: Thanks for adding the trajectory analysis. It is a nice addition. Especially the length of track vs. ellipse size

Section 3.3: This is probably my only real CRITIQUE here: You discuss cut-off low C3 being responsible for the thunderstorm activity over southeast Germany, central France and the Netherlands. However, from your figure 5e it rather seems to be cut-off low C1. The cut-off low detection method seems to join the several smaller cut-offs or filaments. However, the center of C3 is still over the Atlantic ocean? I would at least write a clear comment here or rename the identified cut-off low blob in Fig 12. In my opinion, C3 is just embedded in a larger scale system - and so is C1 (which seems to be rather associated with the thunderstorms).

5. Discussion: lines 540-541: "Interestingly, atmospheric blocking was key to providing the large-scale setting conducive for
convective in its vicinity." - There seems to be a word missing after convective?

6. Summary and Conclusions: line 584: "(iii) the large cut-off low frequency that was responsible for the majority of convection triggering" - I would rather say "associated with" instead of "was responsible for", because: Could you really prove that the cut-off lows were responsible?

Fig 5. : I like the blue dots! It would be good to comment on the dots in the main text as well!

Overall, the quality of the figures is good.

Hide

ED: Publish subject to minor revisions (review by editor) (08 Jun 2020) by Martin Singh

AR by Susanna Mohr on behalf of the Authors (18 Jun 2020) Author's response Manuscript

ED: Publish subject to technical corrections (03 Jul 2020) by Martin Singh

AR by Susanna Mohr on behalf of the Authors (03 Jul 2020) Author's response Manuscript

Short summary

We investigated an exceptional thunderstorm episode in 2018, in which atmospheric blocking provided large-scale environmental conditions favouring convection. Furthermore, blocking was accompanied by a high cut-off frequency on its upstream side, which together with filaments of high PV provided the mesoscale setting for deep moist convection. The exceptional persistence of low stability combined with weak wind speed in the mid-troposphere over more than 3 weeks has never been observed before.