This paper offers an interesting analysis of flash droughts in a region that is often underseen in this context. The text is well-written and presents relevant insights about the emergence and trends of flash droughts in the UK, analysing their relationship with atmospheric and oceanic conditions such as the North Atlantic Oscillation. The authors also present a relevant methodology for identifying the influence of evaporation on the onset of flash droughts. In addition, the authors robustly expose methodological limitations and suggest possible directions for future research based on their findings. However, some justifications and explanations need further clarification.

General comments:

Firstly, the methodology for identifying flash droughts is not sufficiently clear, especially with regard to the application of the SPEI thresholds at the one-month and weekly scales, as well as the maximum duration that a drought event can have to still be considered a flash drought (Lines 193 to 203). I suggest the authors to provide more details on these aspects rather than indicating a citation where these details can be found (Lines 206 to 207).

Another methodological aspect that I believe is not clear enough and that I have some questions about is the evaluation of the influence of AED on triggering flash droughts. The authors propose comparing the SPEI calculated using conventional time series of precipitation and AED with the SPEI calculated using a fixed AED based on the weekly average. Was it the average weekly AED of the month analysed, the average weekly AED of the year analysed within the period 1969 to 2021, or the weekly average of all the years between 1969 and 2021? (Lines 223 to 236). I wonder if using this methodology, which relies on a SPEI calculated only with a weekly average compared to the conventional SPEI, is sufficiently appropriate to achieve the stated objective. If the AED time series is highly variable, could using averages lead to the emergence of a more influential pattern during periods of more anomalous AED? This could potentially explain, for example, why a clear contribution to the emergence of flash droughts was observed basically only in spring (e.g., Lines 375 to 377, 490 to 491, and 522 to 524). The authors could clarify how this weekly average was used and provide more details about the seasonal variability of the AED time series. Would it be possible to identify the influence of AED on the emergence of flash drought by comparing the SPEI and SPI, both calculated on the same time scale and with the same statistical distribution? Since the SPEI identifies more flash drought events or greater intensities when compared to the SPI, this would be evidence of the AED contribution to the emergence of this type of drought. This approach seems more straightforward and intuitive to me. Could you comment on this?

Would it be possible to compare the flash drought identification results shown in Figures 1 and 2 with historical records of this type of drought? This could work as a way to validate the methodology used. The UKCEH provides a range of information on droughts in the UK on its website (https://www.ceh.ac.uk/our-science/projects/drought-inventory), with data dating back to 1890. For example, within the presented methodology, were more flash droughts identified during years characterized by major drought events in the study area (e.g., 1975-1976, 2004-2006, or 2010-2012)? Could these events be the result of a succession of flash droughts? Or are flash droughts associated with longer drought periods? In this context, it would be interesting if the authors could add a result showing the intra-annual variation in the number of flash drought events.

The authors highlight that in some parts of the UK a positive trend in the number of flash drought events has been identified. What percentage of the area showed a significant trend? From Figure 4 it appears to be a fairly small and dispersed area compared to the rest of the UK. Could this be related to some bias in the creation of the precipitation and AED products used?

Minor comments:

Is AED exactly the same thing as PET? It's not clear (Lines 170 and 171).

I consider it too strong a statement to say that the influence of AED on triggering flash droughts has been assessed in relation to the global warming process, especially since no analyses of climate change projections or model outputs of this kind have been used (Lines 634 to 635).

This manuscript focuses on flash droughts in the UK. It explains the characteristics and changes of flash droughts from the perspectives of precipitation, atmospheric evaporation demand and circulation conditions. Overall, the structure is clear and the topic is interesting.

There may be issues mainly in the following aspects: 1. The introduction is a bit lengthy and does not seem to clearly outline the research progress of flash droughts (instead of providing a broader overview of drought research in general). 2. The description of the definition of flash droughts is rather brief. I believe the definition of flash droughts might be crucial since there is currently no consistent definition. 3. All the results are qualitative. Although there is extensive discussion, some quantitative results could be incorporated. My specific comments are as follows:

Abstract

L23: This paper has divided the regions into three zones (North-West, Transition, and South-East). It's best to avoid using other directional terms (e.g., central and northern regions), at least in the Abstract.

L27-29: When I read this sentence, I thought this paper was about the relative importance of various factors to flash droughts (e.g., "responds primarily to precipitation variability; AED is important as a secondary driver"). However, the later sections only analyze precipitation and AED.

L31-33: The conclusions can be reconsidered. Does "this relevance" refer to the contribution of AED to flash droughts? I didn't see a correlation analysis. The later sections also don't provide an analysis of how atmospheric and oceanic conditions impact precipitation and evapotranspiration anomalies, only the situation during the onset of flash droughts.

Introduction

The overall structure seems a bit confusing. For example, the second paragraph is lengthy and vaguely introduces current research progress, mentioning the "gap" and then "This study focuses on...," but then expands into several more paragraphs of other research progress.

Secondly, most of the progress discussed is about drought rather than flash drought. For instance, the fourth and fifth paragraphs (starting from L100). There are many articles on the impact of precipitation and evapotranspiration on flash droughts and how flash droughts change under climate warming, which may need further review and revision.

Thirdly, the statement "no studies previously analysed specifically the occurrence of flash droughts in the UK" is not quite accurate because global or European studies also cover the UK. The review of related progress is lacking.

Data and Methods

L196-198: I couldn't understand this definition until I read the reference by Noguera et al. (2020). A more detailed description and a diagram might be needed to clarify this definition.

L198-L200: Using a four-week window to determine ΔSPEI<-2 only describes the onset of a flash drought. If the onset is very rapid (e.g., within two weeks), it might also "expect some impact." The impact of a flash drought is more related to the entire duration rather than just the onset time (e.g., vegetation might not show negative responses if the flash drought recovers quickly). The description might need to be checked.

L229-L231: I'm not sure if this underestimates the contribution of AED to flash droughts because if precipitation anomalies are sufficient to cause a flash drought, the further exacerbation by AED might be unnoticed.

L249-L250: It seems flash droughts are identified on individual grid points. How are the top-10 flash droughts selected based on the largest affected area (e.g., number of contiguous grid points)? Also, I'm curious about how seasonal distinctions are made since there could be cross-seasonal flash droughts. How are these divided?

Results

L394-398: I don't quite understand how the changes in precipitation and AED explain the increased contribution of AED to flash drought. The trends of these variables don't seem to match. This might be because flash drought trends are influenced not just by changes in mean precipitation but by variability? I suggest examining how flash droughts change when considering only precipitation (SPEI_PRE in your method)—whether they increase, decrease, or remain unchanged. Then, analyze how they change when considering AED, to explain the relative contribution.

Discussion

L519-520: Please add figure citations (e.g., Figure 1) to the relevant conclusions.

####Line Edits####

L20: affected -> have affected (consistent tense)

L31: evidenced -> evidence

L91: delete " ; "

L165: The full name of PET is potential evapotranspiration

L369: No need to define the abbreviation again

L408: Change to "is only"

L435: develop -> development, ocurred -> occurred