To quantify the behaviour of Mediterranean cyclones, we use a model chain from global to regional scales. The global model delivers the initial and boundary conditions for the regional model. The Community Earth System Model CESM version 1.2.2; serves as global model. used this model to perform a late Holocene simulation, spanning 3600 years from 1500 BCE until 2100 CE (using the representative concentration pathway RCP8.5 scenario from 2012 to 2100). The output of this simulation has a temporal resolution of 6 h and a spatial resolution of 1.9° (latitude) × 2.5° (longitude) in the atmosphere and over land, and a nominal 1.0° × 1.0° resolution for the ocean and sea ice. The CESM simulation contains 30 vertical levels. In this study, we focus on the period from 1821 CE to 2100 CE (280 years) to capture both the pre-industrial and the future climate.

As RCM, we use the Weather Research and Forecasting (WRF) model version 4.3 for dynamical downscaling. WRF is a mesoscale model that is based on the non-hydrostatic equations and a set of parameterizations to represent sub-grid-scale processes. We used the set of parameterization schemes listed in Table . For the Noah-MP land surface model, the phase change of glaciers is turned off, since this option causes numerical instabilities in our simulation.

The 280 years of the CESM simulation are dynamically downscaled to a horizontal resolution of 20 km and 49 vertical levels. A fixed time step of 120 s is used, and the data is stored with an hourly temporal resolution. To save time, we split up the 280 years in roughly 35 year chunks that always overlap for 2 years in time. The 2-year overlap is used as spin-up time for each chunk. Note that the land and atmosphere usually reach equilibrium after 6 to 12 months . We use a single-domain setup covering the Euro-Atlantic area (Fig. ). Nudging to the large scale circulation of the CESM simulation is switched off, as the main cyclogenesis regions for Mediterranean cyclones are within this domain, and cyclones forming within this domain could develop their own dynamics independent of CESM input data. Although a horizontal resolution of 20 km is insufficient to numerically resolve convective processes, it is sufficient to accurately represent cloud-diabatic processes in fronts and conveyor belts that are crucial features in extratropical cyclones .

Extratropical cyclones are tracked with the cyclone tracking algorithm developed by , which is extended by and . It has been shown that this algorithm can represent cyclones realistically .

The algorithm tracks minima in the geopotential height field, and we apply it to the hourly 850 hPa geopotential height (Z850) field in WRF. Since tracking cyclones in the lower atmosphere at higher resolution is difficult, due to the complex Mediterranean topography, we regrid the Z850 field of the WRF simulation to 1° × 1° resolution (roughly 100 km). The regridding excludes weak and unphysical lows. Additionally, we apply a linear smoothing of all grid cells within 2° of one grid cell. With this, we prevent cyclone tracks from being split into multiple tracks. To further limit the number cyclones, the following criteria of identified local minima must be met:

A minimum mean gradient of at least 20 geopotential meters (gpm) per 1000 km.

Since the cyclones are tracked on the 1° × 1° Z850 field, the location of the cyclones often does not match the actual Z850 minimum in the higher 20 km resolution data. Therefore, for every point within the cyclone track, we search for the actual Z850 minimum in the higher resolution Z850 field within a 100 km radius of the original cyclone track point. Next, we assume a cyclone radius of 500 km which corresponds to the average radius found for Mediterranean cyclones . We use this cyclone radius to exclude wind speed and precipitation that are not cyclone-related.

To compute how extreme each cyclone track is, we perform the following procedure for the WMED and EMED respectively:

To select the most intense wind speed EXCs, we only consider the 95th-percentile 850 hPa wind speed (WS850) of all grid cells within the predefined 500 km cyclone radius. This is only done at the time the cyclone reaches its minimal sea level pressure. The time of minimum core pressure, defined as tslp, is a solid indication of when a cyclone reaches its highest wind speed .

To highlight the climatological differences within the Mediterranean, we split up the Mediterranean into two regions (two red boxes in Fig. ), namely the western Mediterranean (“WMED”, between 0–17.5° E and 30–47° N), and the eastern Mediterranean (“EMED”, between 17.5–40° E and 28–42° N). All analyses are performed for each region separately.

To assess the effect of climate change on Mediterranean cyclones, we use two 60-year periods. The first period is defined as all winter half-years (ONDJFM) starting in October 1821 until March 1881 and roughly representing the pre-industrial climate. The second period is defined as all winter half-years from October 2039 until March 2099 representing the future climate under the RCP8.5 scenario. These periods and the EXCs within these periods will be referred to as past and future, respectively.

We apply a Kolmogorov–Smirnov (KS) test in the analyses to test statistical significnace at the 5 % level. For the location, we use KS test to see if the median latitude and longitude of the future EXC changes. For the seasonality, we use the KS test to examine whether future EXCs occur at different times. This is done by analysing the median day-of-year of each EXC type changed for each region and time period.

Finally, a cyclone-centred composite analysis is performed on the 50 most extreme EXCs found in the WMED and EMED, respectively. We identify roughly 1000 cyclones per period and region. For the composite analysis, we select the 50 most extreme cyclones, defined with respect to the 95th percentile of precipitation, wind speed, and wind-precipitation compound EXCs. The analysis is performed for cyclones associated with cyclone-related precipitation, wind, and compound extremes, separately.

For each cyclone track, we set the reference at time tslp for wind EXCs and tprecip for precipitation EXCs. Every track timestep after tslp or tprecip receives a positive index, and the track timesteps before tslp or tprecip a negative index.

We perform the above analysis for the WS850, precip_6 h, and the 200 hPa wind speed (WS200) field. Note that some EXC tracks may initialize later than 12 h before tslp or tprecip, and may also disappear earlier than 12 h after tslp or tprecip. Hence, the composites shown at 12 h before and after tprecip or tslp consists of slightly less than 50 EXCs. To compute whether the differences in spatial means for past and future cyclones are statistically significant we apply a Welch's t-test to the spatial composite.

Furthermore, we compute vertical cross-sections for the 50 most extreme precipitation EXCs along an east–west plane through the cyclone core spanning 1600 km in total. For these vertical cross-sections, we compute PV anomalies, potential temperature (θ) and equivalent potential temperature (θe) for 21 pressure levels up to 100 hPa (50 hPa intervals from 100 to 900 hPa and 25 hPa intervals from 900 to 1000 hPa). PV anomalies are computed by subtracting the daily PV climatology, calculated separately for the past and future period, from the instantaneous PV fields. The climatology is derived by averaging PV for each calendar day and applying a centred 31 d running mean.

We also compare some analyses in WRF to ERA5 reanalysis data for the period October 1981 to March 2011 to capture 30 winter half years. Like in WRF, we track cyclones on 1° resolution in ERA5, but for the EXC composite analysis we use the highest available ERA5 resolution of 0.25°, and regrid the WRF data to the ERA5 resolution for a fair comparison.

First, we characterize the preferred regions of all cyclones in the Mediterranean. Therefore, we use the cyclone frequency, defined by how often a grid cell is located within the 500 km radius of a cyclone in the original WRF grid. The comparison of WRF with ERA5 for the time period 1981 to 2010 shows that WRF overestimates the number of cyclones for most of the domain (Fig. S1 in the Supplement). This is to some extent expected as WRF is higher resolved. Regionally, the main cyclone hotspots extend from Italy towards the Levant in WRF (Fig. S1a), whereas in ERA5 this is more confined to the region around Italy (Fig. S1b). Thus, biases in cyclone frequency are evident over the eastern Mediterranean and eastern Europe (Fig. S1c), whereas biases over the western Mediterranean are small.

Regions of high cyclone frequency exhibit the highest cyclone frequencies in both the past (up to 0.09 cyclones d⁻¹; Fig. a) and the future (up to 0.07 cyclones d⁻¹; Fig. b). Comparing the future with the past period, a decrease in cyclone frequency is evident (Fig. c). Apart from a few regions in northern Africa, all regions in the Mediterranean show a decline in mean cyclone frequency. This is particularly true for the hotspot over Italy and the Anatolian Plateau, which show the largest absolute decrease in cyclone frequency (up to 0.02 cyclones d⁻¹), which in relative terms indicates a decrease of roughly one-third.

Besides the mean cyclone frequency, also the spatial distribution of the 50 most extreme EXCs is analysed. In Fig.  the locations of past and future EXCs for each region and each category are shown. In the WMED (Fig. a–c), wind speed EXCs are distributed over the entire domain, whereas precipitation and compound EXCs cluster over the warm waters of the Tyrrhenian and Adriatic Sea, and over Northern Italy. Future precipitation EXCs in the WMED (Fig. b) occur less often over the Mediterranean and Ligurian Sea. In the EMED (Fig. d–f), all EXC types cluster in the Ionian and Aegean Sea, and over northern Greece and the Anatolian Plateau. Future precipitation and compound EXCs (Fig. e and f) shift south towards the Mediterranean Sea.

Additionally, we show histograms of the longitudes and latitudes (Fig. ) to investigate whether the median location of EXCs changes as a result in the future. The southward shift of precipitation and compound EXCs in the EMED in the future is statistically significant at the 5 % level. We also find a significant eastward shift of compound EXCs in the WMED in the future (Fig. c), and of wind EXCs in the EMED (Fig. d). The latter is caused by the cluster appearing in the Levant in the future.

Besides the spatial changes, we also investigate changes in the seasonality of EXCs during the extended winter season. In Fig. , we show the number of EXCs that occur every month of the winter half-year for the WMED (Fig. a) and EMED (Fig. b) in the past and the future. Wind and compounding EXCs occur evenly over the entire winter half-year in both regions. Yet, wind EXCs occur more frequently in the second and colder part of the winter half year, whereas compounding EXCs are more frequent during the beginning of the winter half-year. The occurrence of precipitation EXCs (blue bars) peaks in autumn when the Mediterranean Sea is still warm and able to provide moisture to the atmosphere. In the second half of the winter half year precipitation EXCs become rare in both regions. The decrease in precipitation EXCs is very abrupt in the WMED, and more gradual in the EMED. Comparing the past with the future EXC distribution, we do not find a statistically significant change in the median time of occurrence of any EXC type in any region. Thus, the seasonality of extreme cyclones remains unchanged under future RCP8.5 conditions.

In this section, we assess the life cycle of precipitation EXCs using a composite analysis. In Fig. , the 50 most extreme precipitation EXCs are shown for the WMED and EMED, assessing past and future EXCs before, at and after their most intense precipitation phase tprecip. In all composites, we see the structure of a cyclone with a clear minimum in sea level pressure and precipitation bands north and southeast of the EXC centre.

First, we analyse the life cycle of past precipitation EXCs (Fig. a–c and j–l). 12 h before tprecip (left column), the highest precipitation is located north of the EXC centre in both regions, with the highest precip_6 h values located very close to the EXC centre (Fig. a, j). This is in agreement with ERA5 as the comparison for the period 1981–2010 shows, although WRF overestimates precip_6 h 12 h before tprecip (Fig. S2). In the EMED, a precipitation band southeast of the EXC centre is present, which indicates the development of frontal structures (Fig. j). At tprecip (Fig. b, k), precipitation further intensifies and the development of frontal structures southeast of the cyclone core is evident. Highest precip_6 h values are still located north of the EXC centre, with precip_6 h values up to and exceeding 25 mm 6 h⁻¹ for past (Fig. b) and future (Fig. e) EXCs in the WMED, respectively. Again WRF agrees with ERA5, but overestimates precip_6 h at tprecip (Fig. S2). In the composites 12 h after tprecip, precip_6 h significantly decreases in both regions (Fig. c, l). Close to the EXC centre, precip_6 h has fallen by 10 to 15 mm 6 h⁻¹. Nevertheless, frontal structures are still apparent in both regions. The decay process is well simulated as the comparison to ERA5 shows (Fig. S2). The life cycle of precipitation follows a general intensification of the pressure field. The core pressure of precipitation EXCs falls by 5 hPa between 12 h before tprecip and tprecip. 12 h after tprecip, the core pressure is still low, which is due to the fact that precipitation peaks before core pressure reaches its minimum.

The life cycle of future precipitation EXCs shows a similar intensification process for precip_6 h and core pressure for both regions (Fig. d–f and m–o). To illustrate the climate change signal in the life cycle, we focus on the difference between past and future EXCs in both regions (Fig. g–i and p–r). First, we consider the composites 12 h before tprecip. A future decrease of precip_6 h around the EXC centre in both regions appears. In the WMED, this decrease is rather minor, and not significant (Fig. g). In the EMED (Fig. p), precip_6 h decreases up to 8 mm 6 h⁻¹, i.e., a decrease of almost half. Notably, precipitation increases significantly further away from the EXC centre in the EMED. The reduction in precipitation is less at tprecip. For precipitation EXCs in the WMED (Fig. h), a dipole pattern forms with a significant increase in precip_6 h just north of the EXC centre and within the frontal zones southeast of the EXC centre. A significant decrease in precipitation just south of the EXC centre appears. The areas where precip_6 h increases also overlap with the areas where precip_6 h is highest already (Fig. b and e), thus indicating an increase in the impact of future precipitation EXCs at tprecip in the WMED. In the EMED, a decrease in precip_6 h is still apparent around the EXC centre at tprecip (Fig. q), although the magnitude of the decrease is smaller and the signal is not statistical significance. Thus, the results suggest that at tprecip, precip_6 h increases in precipitation EXCs in the WMED and stays roughly the same in the EMED. The difference between the regions remains in the composites 12 h after tprecip. In the WMED, we find a significant precip_6 h increase of roughly 5 mm 6 h⁻¹ north of the EXC centre (Fig. i). This is a doubling compared to past precipitation EXCs (Fig. c).

At 12 h before tprecip, future extreme precipitation EXCs are slightly less deep in terms of core pressure compared to past precipitation EXCs in both the WMED and the EMED. This suggests that future precipitation EXCs are less intense with respect to pressure before their mature stage, providing a partial answer to why future precip_6 h decreases compared to the past in both regions. At tprecip, precipitation EXCs are equally deep for the past and future in the WMED where future precipitation EXCs deepen more quickly in 12 h (Fig. a–b vs. Fig. d–e). In the meantime, the higher core pressure for future precipitation EXCs persists in the EMED (Fig. k vs. Fig. n). This could explain why precip_6 h in the WMED increases, in contrast to the EMED. Also 12 h after tprecip, the difference in core pressure between the WMED and EMED persists.

To further explain why future precipitation WMED EXCs are stronger in their mature phase, we show vertical cross-sections of PV anomalies, potential temperature (θ) and equivalent potential temperature (θe) within the composites of Fig. . We focus on 6, 9 and 12 h after tprecip, as differences in PV between past and future EXCs only emerge in the mature phase of the cyclone.

In all sub-panels of Fig. , we find higher θ and θe values in the right half of the vertical cross-sections and lower values in the left half, highlighting the warm and cold sector of the EXCs, respectively. In the warm sector, θ and θe differ more than in the cold sector, indicating the greater moisture content of the warm sector . Besides, the negative vertical gradients in θe in the lower part of the troposphere (e.g. in the right-hand side of Fig. e) points to convective instability, which can contribute to precip_6 h that we observe in Fig. . Both θ and θe increase for future EXCs (Fig. a–c) vs. Fig. d–f), but θe in the warm sector increases up to 9 °C, showing a combined increase in temperature and moisture in the atmosphere in the future, which further explains the increase in precipitation of EXCs in WMED.

Looking at PV anomalies, we also find future changes in the vertical structure of PV (Fig. ). In all composites around 300 hPa, we identify high PV air in excess of 2 PVU (indicated by the yellow line) indicating the stratospheric air masses. The high PV anomalies above the yellow line indicate a lowering of the tropopause in the vicinity of precipitation EXC. This is in contrast to the upper atmosphere east of the cyclone centre, which is dominated by negative PV anomalies indicating a higher than usual tropopause. Additionally, so-called PV towers extend though the entire troposphere are present in the cyclone centre (Fig. ). These PV towers consist of high-PV stratospheric air intruding into the top of the PV tower, and diabatically produced PV in the lower troposphere. The lower part of the PV towers exhibit sufficiently large PV values such that the 2 PVU line appears in all composites. Overall, we see the same structures also for precipitation EXCs in the EMED (Fig. S6a–f).

Considering the future differences in Fig. g–i, we see a decrease of PV near the tropopause in the warm sector, indicating the lifting of the tropopause. In the cold sector, PV increases near the tropopause, which indicates stronger PV advection from the stratosphere and is also indicative of a more intense baroclinic cyclone. Interpretations should be taken with care, though, as the changes observed near the tropopause are at most marginally statistically significant (at the 5 % level). Still, this enhanced advection of high PV air for precipitation EXCs is not found in the EMED (Fig. S6g–i). The PV values within the lower part of the PV tower increase for future precipitation EXCs (Fig. g–i). This is particularly apparent at 9 h and to a lesser extent at 12 h after tprecip (Fig. h and i) with increases up to 1 PVU. Although the increase is marginally significant, this still indicates an increase of up to 50 % in instantaneous PV in Fig. h. This is most likely due to an increase in diabatically produced low-level PV as a result of more moisture and hence higher latent heat realease in future WMED precipitation EXCs. This may enhance the cyclonic circulation and provide a mechanism of why future WMED precipitation EXCs exhibit a stronger intensification and stay more intense in their mature phase. We also see an increase of PV in the PV towers associated with future precipitation EXCs in the EMED, but this increase is clearly less robust (Fig. S6g–i).

In this section, we investigate the life cycle of the wind EXCs, following a similar strategy as with precipitation EXCs. In Fig. , we find that the highest WS850 values are generally located just south or southeast of the EXC centre with WS850 values of up to 25 m s⁻¹. Minimum core pressure falls below 990 hPa in most composites, and core pressures are generally up to 10 hPa lower than for precipitation EXCs. Also, the isobar spacing is wider, indicating a weaker pressure gradient.

The life cycle of past wind EXCs and its associated wind field is shown in Fig. a–c and j–l. 12 h before tslp (left column), the wind EXCs is already substantially deep, and the wind field is strongest south and southeast of the core. The comparison with ERA5 for the period 1981–2010 shows that WRF represents this state but overestimates WS850 in wind speed EXCs (Fig. S3). EXCs in the WMED (Fig. a and d) are slightly deeper and more intense than wind EXCs in the EMED (Fig. j and m). At tslp (middle column), the wind EXCs has deepened around 4 hPa in all composites. The wind field has clearly intensified and expanded, especially in the EMED. Wind EXCs in the WMED are slightly deeper than in the EMED (roughly by 4 hPa), and achieve higher WS850 values in the EMED. A difference between the two regions is that wind EXCs in the EMED have a much more southwest-northeast orientation than in the WMED. WRF agrees with ERA5 but shows an even stronger overestimation of WS850 in wind speed EXCs by up to 6–8 m s⁻¹ than hours before tslp (Fig. S3). 12 h after tslp (right column), the core pressure of the EXC has increased, and the wind field has shrunk in size and intensity. We also see a general shift of the remaining wind field towards the east relative to the EXC centre compared to the composites 12 h before tslp, especially in the WMED. WS850 in the EMED (Fig. l and o), is slightly higher than in the WMED (Fig. c and f) by about 2–3 m s⁻¹ at tslp. Again the general decay behaviour of WRF is resembling ERA5 but the overestimation of WS850 in wind speed EXCs persists (Fig. S3).

The life cycle of future wind EXCs intensifies in a similar way as the one of past wind EXCs (Fig. ). To extract the future climate change signal, we show the difference between the past and the future (Fig. g–i and p–r). 12 h before tslp (left column), in the WMED (Fig. g) we find a complex pattern of WS850 changes near the EXC center, with opposing anomalies largely offsetting each other. 750 km east of the EXC center, the wind speed is signifcantly increased by up to 4 m s⁻¹ in the future. In the EMED, we also find a complex pattern in wind speed differences between the past and future (Fig. p) which is different to the WMED. The EMED wind cyclones show an increase in wind speed west and east of the cyclone core and a decrease south of the cyclone core. This is mainly due to differences in wind field orientation, as the analysis of the shape of past and future EXCs (Fig. j, m) suggests.

At tslp (middle column), we see a more axisymmetric pattern in wind speed differences. In the WMED, an increase in WS850 appears (Fig. h) that is consistent along the composite, with a significant increase in WS850 in the southeastern quadrant of the composite, which is also the quadrant with the highest WS850 overall. Only in the western half of the EXC do we observe a decrease in WS850, but this decrease is not statistically significant. Unlike the WMED, in the EMED we observe a statistically significant increase in wind speed in the western half of the EXC composite (Fig. q). Comparing the shape of the wind field between past and future EXCs (Fig. k, n), this increase is mainly induced by a small wind field just west of the core for future EXCs. Apart from that, the wind fields stay similar in size and intensity.

12 h after tslp (right column), the differences are similar to the ones at tslp. Again, we see a significant increase in WS850 in the southeastern quadrant in the WMED and a non-significant decrease in the western half of the composite in the WMED (Fig. i). In the EMED, we see a significant increase just south of the EXC centre (Fig. r). Note that the magnitude of these differences is equal to the ones at tslp (Fig.h and q) but occur at lower overall WS850 values, so the relative difference between past and future wind EXCs 12 h after tslp is greater compared to tslp.

At 12 h before tslp, past and future EXCs in both regions have roughly the same core pressure. At tslp, future cyclones deepen more and core pressure for EXCs in both regions is lower than for past cyclones (roughly 4 hPa). This difference persists 12 h after tslp, where the differences in core pressure increase further. This provides a partial explanation of why wind speed EXCs are stronger in their mature phase.

For wind EXCs we do not find a significant increase in low-level PV that could explain the future intensification observed in Fig.  (not shown). To further understand why wind EXCs in the future are stronger in their most intense and mature phase, we investigate the jet stream as a potential driver. In Fig. , we apply the same composite analysis as in Fig. , but now to wind speed at 200 hPa (WS200) characterizing the strength and location of the jet stream relative to the wind EXCs. The analysis shows that WS200 values are the highest about 1000 km south of the EXC centre, indicating that wind EXCs are usually located on the northern edge of the jet. Furthermore, another branch of high WS200 values is present west of the EXC centre, especially 12 h before tslp and at tslp. This likely reflects the polar jet merging with the subtropical jet. Generally, WS200 is higher in the EMED (exceeding 60 m s⁻¹) compared to the WMED (up to 50 m s⁻¹). This is most likely caused by the more southern location of the EMED region (Fig. ) and thus EXCs tend to be located closer to the subtropical jet.

Considering all composites, a maximum in WS200 is located just south of the EXC centre, which has the typical shape a jet streak. 12 h before tslp, the EXC is located right above the jet streak maximum, where the jet streak neither aids nor inhibits EXC development at this stage. At tslp, the EXC moves towards the left exit of the jet streak, which is the region where upper air divergence leads to rising air motions and hence can provide favourable conditions for a cyclone. 12 h after tslp, the EXC has moved further east relative to the jet streak and is now clearly positioned in the left-exit region of the jet streak. This is especially evident for wind EXCs in the EMED (Fig. j–o).

In the future, we see an increase in WS200 for both regions at all time steps (Fig. g–i). Consequentially, for wind EXCs in the WMED the jet streak clearly appears at all time steps in the future (Fig. d–f) in contrast to the past (Fig. a–c). The jet streak maximum wind speed is up to 10 m s⁻¹ higher compared to past wind EXCs in the WMED and mostly statistically significant across all time steps (Fig. g–i). This eventually leads to future conditions where a wind EXC is located in the left exit of a stronger jet streak in its mature phase (Fig. e–f).

In the EMED, we also identify an increase in WS200 within the jet stream across all time steps in Fig. p–r of up to 10 m s⁻¹. In this region, we also see a significant increase in WS200 northwest of the EXC centre, indicating an increase in strength of the polar jet, especially at tslp (Fig. q). However, this increase is only significant at tslp (Fig. q). Nevertheless, we find future mature wind speed EXCs in the EMED in the left exit of a stronger jet streak. This means that future EXCs in the EMED would also benefit from a more favourable position in the jet streak.

Lastly, we investigate the life cycle of precipitation and wind speed in compounding EXCs. For precip_6 h within compounding EXCs (Fig. S4), we largely see the same patterns as for precipitation EXCs (Fig. ). precip_6 h increases as the cyclone intensifies and decreases strongly again in its mature stage. precip_6 h is slightly less intense than for precipitation EXCs and compounding EXCs have a lower core pressure (in the order of 4 hPa) consistent with higher wind speeds. Also, future precip_6 h changes for compound EXCs are very similar to precipitation EXCs. However, compound EXCs in the EMED get even drier than precipitation EXCs in the future (Fig. S4p–r).

Wind speeds in compounding EXCs (Fig. S5) are of similar intensity at tslp compared to wind speed EXCs in Fig. . The wind field is slightly smaller though. 12 h before tslp, WS850 of compounding EXCs is lower compared to wind speed EXCs in both regions (left column of Fig. S5). 12 h after tslp, WS850 is significantly lower than in EMED wind speed EXCs, but of similar intensity in the WMED (left column of Fig. S5). Compound EXC core pressure is very similar to wind speed EXCs at tslp and 12 h after tslp, but slightly higher 12 h before tslp. The increase in WS850 in future compound EXCs is less in the WMED compared to wind speed EXCs in the WMED (Fig. S5g–i). However, for compound EXCs in the EMED we see a large future decrease in wind speed (Fig. S5p–r), which is contrary to what we observe for future wind speed EXCs (Fig. p–r).