Dear Authors:
Thank you for revising your manuscript following comments from two reviewers. I recognize that you carefully responded to several of their comments. However, after inspecting your responses and the revised manuscript I find that further revisions can significantly improve the quality and readability of your paper. See my more detailed comments below.
Zoltan Toth

Editor's comments
1) Presentation of the material. I share Rev. 1's recommendation in her/his 3rd general comment. I understand you consider the data assimilation part of your paper as your main contribution. The sequence in which you present the material, however, should be driven by the natural flow or chain of thoughts, not what you wish to emphasize most. As Rev. 1 noted, the current layout unnecessarily hinders readers efforts to understand your arguments and experiments. There can be other ways you can put emphasis on the DA part. A few related suggestions:
a) Clearly separate the presentation of your model and DA methods. In the revised manuscript, you have to discuss model related questions in the DA section, just because you placed it prior to the modeling section.
b) Switch sections 2 & 3. By introducing your model first you will give the context for your DA discussion. Without understanding the model, one cannot understand or appreciate your DA innovation.

2) Choice of benchmark. In her/his first comment, Rev. 2 asks about a benchmark more appropriate than climatology. While I am not sure I understand her/his specific suggestion, I fully agree that a more proper benchmark for your new DA approach is needed to convince the readers of the value of your methodology. In the manuscript you point ou how you go beyond past methods (e.g., l. 602). Lacking your methodology, how can people initialize an SP model? Can you demonstrate what benefits switching to your new method would bring? A comparison to climatology or observations will not provide that information.

3) Abstract and Conclusions. After addressing the comments above, you may be in a better position to clarify, at a general / conceptual level, what innovations your method provides to the field, and within that, to SP initialization. It may be helpful if you could be more specific in the Conclusions as to how the technique could be applied in real forecast situations. That would nicely complement your summary.

Dear Authors,
Thank you for the careful revision of your manuscript which became much improved. We received feedback from two reviewers, both suggest minor changes. Please consider their comments and introduce any changes necessary in your manuscript. I will take a quick look at your revised manuscript prior to final acceptance for publication. With regards
Zoltan Toth

Dear Authors,
Thank you for your response to the second round of reviews, and especially for the addition of section 4.1. With all the revisions your paper is much improved and is ready for publication in NPG. Congratulations and thank you for choosing NPG for the publication of your research results.
Zoltan Toth