Analysis of a Case of Supercellular Convection over Bulgaria: Observations and Numerical Simulations

Round 1

Reviewer 1 Report

See attached file

Comments for author File: Comments.pdf

Author Response

We would like to thank the reviewer for valuable comments and questions. We hope that we managed to address all reviewer’s comments in the pdf. The manuscript has undergone major revision thanks to reviewer’s suggestions.

Author Response File: Author Response.pdf

Reviewer 2 Report

Substantive comments:

More details are needed through much of the methodology section. For instance, is the ECMWF lightning parameterization solely based on CAPE and shear? Are the WRF domains one-way or two-way nested?

My primary concern with the manuscript is that your ensemble is not well defined. How was the ensemble created (i.e., what is being varied)? Are model parameterizations changed? Boundary conditions? Initial conditions? These details must be provided.

Given that this is a supercell, it would be worthwhile to compare the motion to the Bunkers right-mover vectors (e.g., Bunkers et al. 2000).

Lines 253-254: The radar reflectivity factor of 25 dBZ seems very low and does not appear to be consistent with your references. Can you be more specific by what you mean here and where you found it?

In Fig. 5, it is difficult to determine where the circled couplet corresponds to the reflectivity image on the left. As it stands, I'm not convinced that what you've highlighted is indeed the mesocyclone; it appears to be more clearly associated with divergence than rotation. Double-check the location compared to the reflectivity imagery, and perhaps mark the zoomed region on the reflectivity panel, as well.

In terms of the VIL discussion, mean VIL does increase with reported hail size; however, severe hail is not necessarily consistent with a specific range of VIL. I do not think this discussion is worth including in the manuscript.

Lines 522-523: Your statement beginning with "...it is very likely that..." is not well supported here. You are running the calculation on one particular member, not on a "cluster of well-performing ensemble members". Reconsider your wording here.

Minor comments:

Lines 79-80: While moisture is implicitly part of the CAPE calculation, you can have large CAPE with only a modest layer of appreciable moisture. You could consider revising this section.

Lines 81-82: While this is probably an acceptable explanation here, your description of convection initiation is rather simplified.

Line 102: "Precipitation skill" is vague. What is meant by that? Consider expanding on this idea.

Lines 120-121: I would recommend noting here that you plan to analyze the case in Section 3, as I suspect many readers will not be familiar with the case.

Line 223: NIMH has already been defined, so no need to define it again here.

Line 245: Since you mention "three" main stages, maybe remove the initial stage? Or change this to four.

Lines 291-293: New convection would also be associated with the cold pool lifting parcels to their LFCs.

Line 325: "maximum vertical development" using what metric?

Lines 340-342: Are there any more recent lightning studies that corroborate this argument?

Discussion of ensembles, beginning at line 454: Could the cyan ellipses be associated with later storms? It is not clear based on these figures if each ensemble member generates only one storm around that area or more than one.

Lines 460-462: Was this the first time that any rotation was evident?

Lines 538-540: Are you certain these are simulated supercells if they are moving with the mean wind?

Lines 639-640: Given a sample size of just one case, I would be a little more tenuous with your argument regarding the LINET data.

Suggested wording/grammar changes:

Line 40: Replace "for its severity" with "of its potential severity".

Lines 53-54: "The supercells produce lightning which characteristics are the subject of many studies." is an awkward sentence. I suggest revising.

Line 69: Place "a" before "lightning jump"

Line 72: Place "However," before "Lang et al."

Line 93: Replace "driving larger scales" with "larger scales"

Line 208: Place apostrophe at the end of "CAMs"... CAMs'

Line 220: Rather than a hyphen, use a colon after "damage".

Line 253: Erroneous space after "studies"

Line 257: "convectively" should read "convective"

Line 358: "number positive" should be "number of positive"

Line 359: Erroneous space in "positive strokes"

Line 400: "2015" should be "2018"

Line 459: "favorable" should read "favorably"

Line 505: Erroneous space before period

Line 611: Replace "the earlier convection initiation" with "timing of convection initiation"

Line 645: Replace "disagreement the" with "disagreement with the"

Author Response

We would like to thank the reviewer for helpful comments and suggestions which improved significantly the manuscript. The replies to reviewer’s comments are in the pdf.

Author Response File: Author Response.pdf

Reviewer 3 Report

 

Title: Analysis of a case of supercellular convection over Bulgaria: observations and numerical simulations

Authors: Chipilski et al.

RECOMMENDATION: Minor Revisions

 

This paper deals with the analysis of a supercell that affected Bulgaria on May 2018, using both observations and numerical simulations. The focus of the paper is in particular on the predictability of the case study, both from a long term (global model) and short term (regional model) perspective.

 

The paper is well organized and written, and it is appropriate for publication in Atmosphere after some comments of moderate relevance are properly addressed.

 

Major points:

 

-The main problem I see in this paper is the quality of the Figures. Many of these are not at publishable level, so I recommend the Authors to take care of this problem already at this stage. In particular:

Figures 3-6: the characters in the figures cannot be read; please improve the resolution or, as an extreme solution, remove the characters from the figures;

Figures 11, 13, 14, 16, 17: the country border can be detected hardly in radar images, so that comparison can be performed very hardly;

 

-I think the results of the present paper should be better connected with the international framework this study belongs to. For this reason, I suggest to further comment the results of your paper in the Discussion, in comparison with other relevant papers on the predictability of supercells; a few are reported hereafter:

 

D. J. Stensrud, J.-W. Bao, and T. T. Warner, 2000: Using initial condition and model physics perturbations in short-range ensemble simulations of mesoscale convective systems, Monthly Weather Review, vol. 128, no. 7 I, pp. 2077–2107. 

Mansell, E. R., 2008: EnKF analysis and forecast predictability of a tornadic supercell storm. Preprints, 24th Conf. on Severe Local Storms, Savannah, GA, Amer. Meteor. Soc., P5.2. 

A. Aksoy, D. C. Dowell, and C. Snyder, 2010: A multicase comparative assessment of the ensemble Kalman filter for assimilation of radar observations. Part II: short-range ensemble forecasts, Monthly Weather Review, vol. 138, no. 4, pp. 1273–1292.

C. S. Schwartz, J. S. Kain, S. J. Weiss et al., 2010: Toward improved convection-allowing ensembles: model physics sensitivities and optimizing probabilistic guidance with small ensemble membership, Weather and Forecasting, vol. 25, no. 1, pp. 263–280. 

D. J. Stensrud and J. Gao, Importance of horizontally inhomogeneous environmental initial conditions to ensemble storm-scale radar data assimilation and very short-range forecasts, Monthly Weather Review, vol. 138, no. 4, pp. 1250–1272, 2010. 

R. M. Cintineo and D. J. Stensrud, On the predictability of supercell thunderstorm evolution, Journal of Atmospheric Science, vol. 70, pp. 1993–2011, 2013. 

Wapler, K., and P. James, 2015: Thunderstorm occurrence and characteristics in Central Europe under different synoptic conditions. Atmos. Res., 158–159, 231–244.

Miglietta M.M., Manzato A., and Rotunno R., Characteristics and Predictability of a Supercell during HyMeX SOP1, Q. J. Roy. Meteor. Soc., 142, 2839-2853, 2016.

Miglietta M. M., Mazon J., Rotunno R., Numerical simulations of a tornadic supercell over the Mediterranean, Weather and Forecasting, 32, 1209-1226, 2017.

Flora, M.L., Potvin, C.K., Wicker, L.J., 2018: Practical predictability of supercells: exploring ensemble forecast sensitivity to initial condition spread. Mon. Weather Rev. 146(8), 2361–2379.

Miglietta M. M., Mazon J., Motola V., Pasini A., Effect of a positive Sea Surface Temperature anomaly on a Mediterranean tornadic supercell, Scientific Reports, 7, 12828, 1-8, 2017.

Pilguj, N., M. Taszarek, Ł. Pajurek, and M. Kryza, 2019: High-resolution simulation of an isolated tornadic supercell in Poland on 20 June 2016. Atmos. Res., 218, 145–159

 

Minor points:

- Lines 173-174: “It also accounts for forecast uncertainty by comparing the full CDFs of the ensemble forecast and M-climate.” Please, may you explain this point more in detail?

- Line 209: NEP should be explicitly defined;

- Table 1: did you also test simulations without convection parameterization in the external grid too? The inclusion of cumulus parameterization in the external grid may include an additional level of complexity to your simulations, since the cumulus parameterization is not consistent with both the ECMWF EPS parameterization scheme and with the WRF domain 2 and 3 explicit treatment of convection;

- Lines 213-227: the locations of the places mentioned in the text should be added in Fig. 1;

- Line 270: 17 km is really a high cloud top; may you add some comments on the occurrence of overshooting tops in the region?

- Figure 6: please, may you add circles to identify the presene of the V-notch in the panels?

- Lines 316-318: “These jumps in the flash rate are linked to abrupt increases in the heights of areas of the reflectivity factor of 15 dBZ and 45 dBZ”: I do not see this feature in Fig. 7: can you estimate the correlation of H15dBZ and H45dBZ with TFR? 

- Line 323: what do you mean with “The last TFR jump”? how is “a jump” defined?

- Lines 329-330: in my opinion, for most of the time there is a temporal shift between the two curves, i.e. the evolution of H60dBZ slightly anticipates that of TFR, especially in the second half: can you estimate the correlation in the period and check if there is any shift?

- Line 357: the definition of “multiplicity” is absent;

- Lines 372-379: please, may you add some comments on the interpretation of Fig. 10d?

- Lines 383-384: really, the parameters reach their highest values in south-western Romania: do you know of any reports of severe weather in that region? 

- Line 432-434: “The latter implies a loss of predictability as the numerical solutions of two forecasts initialized from different initial conditions begin to converge to the same value”: the sentence should be reformulated more clearly.

- Line 434-436: is it possible to conclude that the skill of WRF.14may12utc runs is comparable to that of the WRF.15may00utc runs, apart from an earlier evolution of the supercell in the former? considering that the value of NEP is still high at 14:15 UTC in Fig. 14b, it seems that the phase of strong intensity is even better reproduced in WRF.14may12utc than in WRF.15may00utc; please, add a discussion on this point;

- Line 490: please explain shortly the methodology of Clark et al.;

- Line 513: the sentence is not complete;

- Line 519-521: how did you calculate this probability?

- Lines 555-579: this part seems to me too philosophical and long, please reduce it;

- Line 604: “were forecast” instead of “occurred”

- Line 629: reference?

 

Author Response

We would like to thank the reviewer for the constructive questions and comments which we hope improved the revised version of the manuscript. The replies to reviewer’s comments are in the pdf attached.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

See attached file.

Comments for author File: Comments.pdf

Author Response

We would like to thank the reviewer for the constructive suggestions. We hope we managed to address all reviewer's comments in the attached file and in the revised manuscript.

Author Response File: Author Response.pdf

Reviewer 3 Report

The Authors have properly answered to all my requests, thus the paper is ready for publication from my point of view.

A few notes that the Authors may take into consideration to further improve the paper:

Figures 3-6: I cannot still read the characters in the panels, but I think this is also related to the degradation in the pdf file. Anyway, this is a problem more relevant for the editorial office; Figure 6: the circle denoting the V-notch is too large; possibly, you should indicate it with an arrow; The border between Serbia and Romania is missing in the radar images; you may include it in the relevant panels, although this is not necessary.

Author Response

We would like to thank the reviewer for the constructive suggestions which helped us improve the manuscript. The replies to the reviewer's comments can be found in the attached document.

Author Response File: Author Response.pdf

Round 3

Reviewer 1 Report

I'm satisfied with the revisions to this manuscript.

Author Response

Thank yoy very much for the positive feedback.