A Mediterranean Nocturnal Heavy Rainfall and Tornadic Event. Part I: Overview, Damage Survey and Radar Analysis

ATMOS-02354; No of Pages 17 Atmospheric Research xxx (2011) xxx–xxx

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A Mediterranean nocturnal heavy rainfall and tornadic event. Part I: Overview, damage survey and radar analysis

Joan Bech a,⁎, Nicolau Pineda a, Tomeu Rigo a, Montserrat Aran a, Jéssica Amaro a, Miquel Gayà b, Joan Arús c, Joan Montanyà d, Oscar van der Velde d a Meteorological Service of Catalonia, Berlín 38, Barcelona E-08029, Spain b AEMET, DT Balears, Palma de Mallorca, Spain c AEMET, DT Catalunya, Barcelona, Spain d Electrical Engineering Dep., Universitat Politècnica de Catalunya, Terrassa, Spain article info abstract

Article history: This study presents an analysis of a severe weather case that took place during the early Received 16 February 2010 morning of the 2nd of November 2008, when intense convective activity associated with a Received in revised form 5 November 2010 rapidly evolving low pressure system affected the southern coast of Catalonia (NE Spain). The Accepted 14 December 2010 synoptic framework was dominated by an upper level trough and an associated cold front Available online xxxx extending from Gibraltar along the Mediterranean coast of the Iberian Peninsula to SE France, which moved north-eastward. South easterly winds in the north of the Balearic Islands and the Keywords: coast of Catalonia favoured high values of 0–3 km storm relative helicity which combined with Tornado moderate MLCAPE values and high shear favoured the conditions for organized convection. A Downburst Catalonia number of multicell storms and others exhibiting supercell features, as indicated by Doppler Heavy rainfall radar observations, clustered later in a mesoscale convective system, and moved north- Doppler radar eastwards across Catalonia. They produced ground-level strong damaging wind gusts, an F2 tornado, hail and heavy rainfall. Total lightning activity (intra-cloud and cloud to ground flashes) was also relevant, exhibiting several classical features such as a sudden increased rate before ground level severe damage, as discussed in a companion study. Remarkable surface observations of this event include 24 h precipitation accumulations exceeding 100 mm in four different observatories and 30 minute rainfall amounts up to 40 mm which caused local flash floods. As the convective system evolved northward later that day it also affected SE France causing large hail, ground level damaging wind gusts and heavy rainfall. © 2010 Elsevier B.V. All rights reserved.

1. Introduction They demonstrated a clear link between cyclone centres located between the Balearic Islands, and the coast of The particular coastline shape and orographic configura- Catalonia (NE Iberian Peninsula), and concurrent high-impact tion surrounding the Mediterranean basin favours the weather effects over Catalonia. Strong maritime easterly concentration of cyclone activity —often associated with winds associated with deep low-pressure systems affecting hazardous weather— on some specific areas, such as the Gulf Catalonia were already examined during the first decades of of Genoa in the Western Mediterranean northern coast the twentieth century by the pioneer work of Fontserè (1929). (Alpert et al., 1990; Trigo et al., 1999). Jansà et al. (2001) On the other hand, other specific studies evaluated the and Campins et al. (2007) studied the relationship between conditions associated with local severe storms, including Mediterranean cyclones and heavy rainfall and strong wind. tornadic thunderstorms, covering the Western Mediterranean area (Romero et al., 2007; Tudurí and Ramis, 1997). According ⁎ Corresponding author. Tel.: +34 93 5676090. to the tornado and waterspout climatologies in Spain reported E-mail address: [email protected] (J. Bech). by Gayà (2005, 2009), the Balearic Islands and, particularly,

Catalonia are the areas where these phenomena occur more often. Based on a 15-year average over a 30,000 km2 area, typically one tornado per year not exceeding F2 damage in the Fujita scale (Fujita, 1981), is likely to occur in central or southern coast of Catalonia. This is in reasonable agreement with previous general observations and estimates such as those reported in Dotzek (2003). A few tornadic case studies in Catalonia have been reported by Ramis et al. (1997), Bech et al. (2007), Aran et al. (2009), and Mateo et al. (2009). The objective of this work is to describe, document and discuss the event that took place on the first hours of the 2nd of November 2008 when two severe storms associated with an intense low-pressure system affected the southern coast of Catalonia. The thunderstorms produced local flash floods and damaging surface winds, with maximum damage estimated up to F2 in the Fujita scale, in a general context of intense regional wind caused by the synoptic conditions. The study is broken into two companion papers. This is the first one, which gives an overview, a description of the damage, and radar analysis of the event. In the second part (Pineda et al., this issue) a detailed analysis of total lightning observations along the thunderstorms life cycle is performed. The organization of this paper is as follows. In Section 2 a description of the synoptic and mesoscale framework of the event is given, using Numerical Weather Prediction (NWP) analysis and forecasts, radiosonde, Meteosat Second Gener- ation (MSG) satellite and radar and lightning observations. Section 3 describes the damage survey of the affected areas and details the thunderstorm analysis with Doppler radar observations. Section 4 provides a general discussion and Section 5 presents a summary and concluding remarks.

2. Synoptic and mesoscale framework

2.1. General setting

This description is based on 0.5° resolution Global Forecast System (GFS) model output provided by the US NOAA Environmental Modeling Center (EMC, 2003). From these data a suite of specific maps to support storm convective forecasts over Europe are routinely produced in the framework of the European Storm Forecast Experiment (ESTOFEX, http://estofex.org). Daily updated maps are publicly available at http://www.lightningwizard.com/maps; see van der Velde (2007) for a detailed description. A customized version of those maps is used here. The synoptic framework on SW Europe on the 2nd of November 2008 was dominated by a highly baroclinic situation, with an extended upper level trough and an associated surface frontal system extending from Southern Spain along the Mediterranean coast of the Iberian Peninsula to SE France, which moved north-eastward. A low pressure area in the eastern coast of the Iberian Peninsula intensified from 00 to 06 UTC. Some instability in the form of Mixed Layer Convective Fig. 1. GFS analysis and forecasts valid at 2 November 2008 00, 03, and 06 – UTC (a, b, and c respectively) showing mean sea level pressure contours Available Energy (MLCAPE) of 200–500 J kg 1 was present over (black lines, hPa), 500 hPa geopotential heights (coloured contours, gpdam), the sea after 00Z (Fig. 1). The mixed layer considered in and mixed-layer convective available energy, MLCAPE (see shaded colours the MLCAPE field of Fig. 1 is the lowest 1000 m above ground legend, in J kg–1. The position of Catalonia (NE Spain) is highlighted with a level. dashed-line red rectangle in panel b. (For interpretation of the references to fi Since the winds were rather strong and from easterly colour in this gure legend, the reader is referred to the web version of this article.) directions at the surface and southerly directions in mid

Fig. 2. GFS model sequence valid at 00, 03, and 06 UTC 2nd November 2008. Left column (panels a, b and c) shows 0–3 km storm-relative helicity (shaded colours, legend in m2 s− 2), supercell composite parameters (Thompson et al., 2004) contour lines with values 0.1, 0.25, 0.5, 1 and 2, and internal dynamics storm motion vectors (Bunkers et al., 2000). Right column (panels d, e and f) shows 0–1 km wet-bulb potential temperature (contour lines, in Celsius) and 10 m wind streamlines and convergence (shown as streamline colours, with different colours for values −7 −6 −5 −4 −3 −2 −11234567,in10− 5 s− 1; red colours indicate values above 6×10− 5 s− 1). (For interpretation of the references to colour in this ﬁgure legend, the reader is referred to the web version of this article.)

Fig. 3. GFS model sequence at 00, 03, and 06 UTC 2nd November 2008. First row (panels a, b, and c) shows 0–6 km shear (black contour lines, in m s− 1), and 0– 1 km shear (shaded colours, m s− 1). Second row (panels d, e, and f) shows lifting condensation level (shaded colours, in m) and vectors qualitatively indicating the difference between LFC and LCL: smaller means less capping according to LFC–LCL values: short arrows (b500 m), thick arrows (N1500 m), and red arrows (b−300 m). Third row (panels g, h, and i) shows 0–2 km mean wind deep convergence (red contours, plotted at 2, 6, 12, 20, 20, 30 and 42, in 10− 5 s− 1), and Parcel Layer Depth (shaded colours, m). Bottom row (panels j, k, and l) shows 0–2 km moisture transport stream lines (humidity times wind, in gkg–1 ms− 1, red colour indicates high values, above 160 gkg–1 ·m s− 1), 1000–600 hPa minimum relative humidity (shaded colours, %) and moisture upslope ﬂux (in gkg–1 ms− 1, contours ranging from light orange to dark pink are plotted at 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1 1.4 1.7). (For interpretation of the references to colour in this ﬁgure legend, the reader is referred to the web version of this article.)

2.2. MSG, radiosonde, radar and surface observations

MSG satellite images from the Meteorological Service of Fig. 4. a) 2nd November 2008 00 UTC MSG satellite water vapour image Catalonia (SMC) show an area of vigorous convective cloud (6.2 μm) showing the convective development area in the eastern part of the development in the eastern coast of Spain, favoured by the Iberian Peninsula. Features indicated are: vorticity centres (encircled red surface low pressure development, the upper level trough crosses), 300 hPa jets (blue arrows, named J1, J2 and J3), 500 hPa–25 °C area and the presence of associated series of jets: J1, J2, and J3 (as (red dashed line closed contour), 500 hPa trough axis (red dashed depicted in Fig. 4). J1 was about 120 kts, and J2 about 105 kts segments), and 500 hPa ridge axis (swirling red line). Radiosonde stations of Barcelona and Palma de Mallorca are also shown with black crosses. b) 2nd while J3 was 60 kts. J2 triggered convection via potential November 2008 03 UTC MSG satellite infra-red (HRIT) 10.8 μm image with instability at mid and high levels and was related to the false colour brightness temperatures. (For interpretation of the references to cyclogenesis shown in Fig. 1. The analysis of satellite loops colour in this ﬁgure legend, the reader is referred to the web version of this indicates the presence of several vorticity centres (marked as article.) red encircled Xs in Fig. 4). One of them moved along J2 over the coast of Catalonia, where the severe weather took place. – Fig. 4 also shows the 500 hPa −25 °C isotherm indicating the mean surface-layer or most-unstable layer (33 and 80 Jkg 1 presence of a cold core which corresponds to the upper level respectively). Accordingly, most instability indices related to low shown in Fig. 1 (note that the 552 gpdam geopotential buoyancy did not indicate strong thunderstorm potential. curve in Fig. 1 matches approximately the −25 °C isotherm in However, as seen in Fig. 5, the wind shear was remarkable. Fig. 4). Radiosonde-derived storm relative helicity (SREH) values − − Radiosonde data from Barcelona and Palma de Mallorca over Barcelona were 284 m2 s 2 and 145 m2 s 2 for 0–3km are shown in Fig. 5. The cold core at 500 hPa was about and 0–1 km SREH, respectively. Two previous tornadic cases −25 °C at 00 UTC (−17 °C over Barcelona, according to the took place with similar radiosonde proﬁles, particularly at − SMC radiosonde data). CAPE values were null (assuming low levels, and SREH 0–1 km values about 150 m2 s 2 (Aran parcel ascent from the surface) and low if calculated from et al., 2009; Mateo et al., 2009).

Fig. 5. Radiosonde data from Palma de Mallorca (red) and Barcelona (blue) at 00 UTC 2nd November 2008. The hodograph shown is from the Barcelona radiosonde data. (For interpretation of the references to colour in this ﬁgure legend, the reader is referred to the web version of this article.)

Between 00 and 06 UTC sea level pressure dropped about Total rainfall amounts were remarkable during this event, 7 hPa in the southern part of Catalonia and even more in the exceeding 100 mm in 24 h in 4 stations of the SMC network, 2 west of Catalonia, reaching 11.7 hPa (Raimat station), which of them located above 2500 m, in the Western Pyrenees of is a value associated with rapid cyclogenesis development Catalonia. Fig. 7a shows a 24 h precipitation analysis and according to Carlson (1991). Moreover, other typical char- several areas exceeding 90 mm, one of them where the strong acteristics of these systems present in this case are: a) the damaging surface winds took place. Four stations on that area appearance of the low pressure system at the polar sector of a recorded 30′ amounts exceeding 20 mm, and one reached jet (in this case over Morocco pointing towards the Balearic 40 mm; as a consequence, several towns of that area suffered Islands at 00 UTC); and b) a strong thermal boundary, which local flash floods. Comparison of precipitation amounts with was clearly appreciated in the analysis performed using the radar reflectivity loops indicates that high rainfall rates in SMC LAPS system (Albers et al., 1996) over Catalonia (not relatively short time intervals were associated with the shown here). individual thunderstorms that caused damaging winds; Fig. 6 gives an overview of precipitation distribution over however the largest rainfall quantities were due either to Catalonia showing 1-km CAPPI radar reflectivity factor the succession of different intense storms over the same area composites from the SMC Doppler radar network (Bech (along the convergence area shown in Fig. 7b) or by mostly et al., 2004). The sequence covers from 1:30Z to 4:00Z, when multicell systems in high terrain areas in the Western the most intense convective activity, in terms of heavy Pyrenees of Catalonia (Fig. 7a). rainfall, lightning and surface wind gusts, took place. Black The radar hail diagnostic product operational at SMC arrows at 3:00Z and 3:30Z panels, respectively, point (Aran et al., 2007), based on comparing the freezing level approximately to the two main areas of damage at the time with height of radar reflectivity cores exceeding 45 dBZ of maximum surface wind damage. During that period (Waldvogel et al., 1979), indicated moderate to high thunderstorms, mostly organized as single or multicell probability of hail in the thunderstorms responsible for storms, moved NW, coming from the sea. Afterwards (not damaging winds. Hail with diameter b2 cm was confirmed shown in Fig. 6), approximately at 4:30Z, they merged into a on two stations in the vicinity of the damaged areas. larger linear MCS system, moving to the NE. As the system Fig. 7b shows the 10-m hourly averaged surface winds at 3 evolved northward later that day it also affected SE France UTC. A clear convergence line (plotted as a yellow dashed causing large hail (diameter exceeding 2 cm), ground level line) is approximately oriented along one of the maximum damaging wind gusts and heavy rainfall. precipitation areas. As discussed later, the most active

Fig. 6. Radar reﬂectivity factor 1-km CAPPI composite from the SMC radar network on 2nd November 2008. Black arrows at 3:00Z and 3:30Z point approximately to the two main areas of damage at the time of maximum surface wind gusts.

event a damage survey was performed by trained personnel over these two zones to collect damage data and witness reports. Because of the time of the day the event took place no pictures or direct visual observation of the thunderstorm (funnel, etc.) was possible.

3.1. Zone 1: Salou–Reus

According to local reports, the coastal city of Salou was affected by strong winds about 03 UTC, only for a few minutes; somewhat later Reus was also affected with less intensity. Structural damage, rated as F0 to F1 in the Fujita scale, was observed in several buildings, with many windows, balconies and shades broken (see Fig. 9a). Some small areas were also affected by flash floods. A camping area near Salou was particularly damaged with many blown tents and a tossed caravan (Fig. 9). A local sports centre was partially destroyed and many trees fell, some of them on a number of cars. In total, 5 people were injured in Zone 1. Only in Salou there were 137 insurance claims (5 caused by flooding and 132 by wind) reaching 2 million euros. The power supply was cut and railway transport was stopped for about 4 h, mainly because of fallen trees. The analysis of the damage patterns seems to indicate they were originated either by straight line winds or by one or several microbursts (in this case would be wet microbursts) — no evidence of tornadic origin was found.

3.2. Zone 2: Miralcamp

The damage on Zone 2 was focused mainly in the small village of Miralcamp, and to a lesser extent, in surrounding areas. Several high voltage power line towers were knocked down (Fig. 10a) and many houses were badly damaged (Fig. 10b), approximately at 3:30Z. The survey indicated widespread F1 and also localised F2 damage, particularly in forest areas (Fig. 10c). A specific analysis over a 1 km2 of Fig. 7. Analysis of SMC surface observations: a) 2nd November 2008 24 h Miralcamp was performed to examine the damage path and precipitation analysis performed with 165 stations (values expressed in swath patterns. Location recorded with GPS, orientation of mm); the green dotted rectangle indicates the wind damaged area contain- fallen trees measured with compass, and damage intensity in ing Zone 1 and Zone 2 (see Fig. 8 for details). b) 2nd November 2008 3 UTC 10-m hourly averaged wind observations; the dashed line indicates terms of the Fujita scale from the survey were plotted in a approximately the position of a convergence area. (For interpretation of georeferenced map (Fig. 11). More damage surrounding this the references to colour in this figure legend, the reader is referred to the web area was found to the S and N/NE, indicating a damage version of this article.) path following approximately a S to N/NE direction. The Miralcamp plot indicates predominant convergence patterns thunderstorms of the event followed and evolved along that along the path, more intense damage (up to F2) to the right of line. On the other hand, during the event strong winds were the main track (consistent with a cyclonic rotating vortex recorded, particularly on the coastal area and in the Pyrenees moving northwards), and also clear damage gradients, as mountains. Three stations measured wind gusts exceeding shown in Fig. 10c. These elements are similar to those found 100 kmh–1. in previous damage surveys of tornadic events performed by some of the authors of this study as reported in Ramis et al. 3. Damage survey (1997) and Bech et al. (2007, 2009). Though the number of limited data in this case did not allow comparing in detail Two distinct zones, within the main area depicted in Fig. 8 observed damage with simulated path swaths on forests as in suffered structural damage. The first one (Zone 1), mainly Bech et al. (2009) or Beck and Dotzek (2010), the survey urban and periurban, is highly populated and includes the city analysis concluded that the most likely cause of the damage of Salou and Reus, near Tarragona. The second one (Zone 2), was tornadic. The damage path was about 8km long, with mostly rural, includes el Pla de Santa Maria, Cabra del Camp maximum width about 400 m and maximum F2 damage. and Sarral — between these two the small village of These characteristics are consistent with statistical studies Miralcamp is located (not shown in Fig. 8). Miralcamp was relating tornado damage path, length and intensity (Brooks, particularly affected by surface damaging winds. After the 2004).

Fig. 8. Map showing the two zones affected by surface damaging winds: Zone 1 (Salou–Reus, Z1), and Zone 2 (Miralcamp, Sarral, Z2). This map corresponds approximately to the green dotted rectangle shown in Fig. 7a. (For interpretation of the references to colour in this ﬁgure legend, the reader is referred to the web version of this article.)

4. Thunderstorm analyses A first analysis of the two thunderstorms that caused the damage indicates that both were originated from a very In this section a radar analysis of the two thunderstorms intense parent-thunderstorm (hereafter denoted as Cell 1; that caused the damage in Zone 1 and Zone 2 is presented subsequent systems are Cell 2 —affecting Salou— and Cell 3 — using data from the SMC. Pineda et al. (this issue) complement affecting Miralcamp). Thunderstorm splitting is a rather this study with a second part with further lightning data and frequent mechanism of supercell formation in this region of processing. Radar and lightning data from the SMC were the Mediterranean Sea in autumn according to a 4 year combined in a thunderstorm tracking system to allow analysis of supercell thunderstorms in Spain by Quirantes characterization of precipitating convective structures (Rigo Calvo (2007), and could be responsible for the generation of et al., 2008, 2010). Within this system, radar data from Cell 2 and Cell 3. Fig. 12 shows the evolution of selected volumetric scans, such as 12 dBZ echo-tops, vertically inte- parameters of those cells and also the timing of the maximum grated liquid or maximum radar reflectivity factor observed, ground damaging winds observed as well as (bottom left) a and total lightning (cloud-to-ground and intra-cloud flashes) summary of the thunderstorms motion. Between 00:30 and rates are processed. Single radar PPI observations from the 1:30 UTC, Cell 1 and 2 directions differed approximately by LMI radar, located at 0.86 °E 41.09 °N and 910 masl are also 45°. Then apparently Cell 1 died and Cell 3 appeared following shown and discussed in this section. a nearly parallel direction to Cell 2, finally converging. This

Fig. 9. Damage observed in Zone 1. Pictures correspond to Salou, including a) damaged buildings; b) camping with tossed caravan, c) sports centre destroyed, and d) cars affected by fallen trees.

Fig. 10. Damage observed in Zone 2 (Miralcamp area), including a) power line towers knocked down, b) houses badly damaged and, c) wide forest areas with downed trees; the dashed line indicates a sharp gradient of damage.

Fig. 11. Depiction of the damage survey performed over the Miralcamp village, affected by F2 damage. Four towers of high voltage power lines (NW of the picture) — see Fig. 10a— were knocked down during the event.

predominant direction (SE to NW) was followed by most from Salou — though the radar site was on a mountain at storms (not only the two severe thunderstorms) and is the 910 masl. A strong reflectivity core (about 48 dBZ) crossed over one indicated by the Bunkers et al. (2000) storm motion Salou and the Doppler pattern showed clear signs of strong vector (rightmover) in Fig. 2. A possible explanation of the radial shear (see black arrow in Fig. 14). Over a horizontal plane, limited difference between the severe thunderstorms and the the shear pattern would correspond to a strong convergence other storm directions was that the background wind was signature. This could be compatible with the mid-level already high so deviations might have been relatively small. convergence and low-level divergence (typically below 1 km) A remarkable feature was the increase in the total associated with microbursts as described by Wilson et al. lightning rate before the onset of ground damage. Cell 1 (1984); the low-level divergence would not be seen by a radar presented high values of maximum radar reflectivity located on a 900 m mountain as in this case. An alternative (N50 dBZ), with a maximum of about 1 UTC (Fig. 12). At explanation of that shear pattern could be associated with a that time the echo morphology of Cell 1 suggested the mesocyclone rear flank downdraft. The convergence was presence of an inflow notch radar signature, while the located nearest to the concave-shaped sharp reflectivity infrared cloud top image exhibited a clearly expanding anvil gradient of the core in a way that may be typical of a convergent (Fig. 13), indicating a strong updraft as the colder cloud tops base to a mesocyclone, or at least a deep convergent signature extend downwind from the thunderstorm core. Note that fine along the interface of a steep gust front (e.g., Lemon and Parker, detail of the radar echo morphology was hampered by the 1996). The presence of an echo overhang in Fig. 18,andits distance to the LMI radar (about 100 km). persistent nature over 15 min suggests that this convergent Additional radar observations corresponding to the time of signature might have extended upward from the surface and maximum ground damage caused by Cell 2 were further that it may have been a mesocyclone base. examined with the aid of reflectivity and radial velocity PPI Figs. 16 and 17 show a similar sequence covering the scans from the LMI radar displaying base level (0.6°) (Fig. 14) 3:30Z maximum ground damage observed at Miralcamp. In and 3.0° scans (Fig. 15). Note that LMI was only about 20 km this case the thunderstorm of interest (Cell 3) is about 50 km

Fig. 12. Evolution of selected radar and lightning-derived parameters of (thunderstorms) Cells 1, 2 and 3. See inset, bottom left, to locate the Cells (C#). The arrows in Cell 2 and Cell 3 indicate the ground damage. Magnitudes shown in the time-series are: maximum heights of 12 dBZ radar reflectivity echoes (TOP-12, in km), vertically integrated liquid (VIL, in mm), total lightning flash rate (TL/min, in min− 1) and maximum radar reflectivity (Zmax, in dBZ). from the radar. An increase in reflectivity is observed, in rotated with regard to lower levels and looks much more as a agreement with the increase in maximum reflectivity shown typical cyclonic velocity couplet (i.e. with azimuthal shear, in the Cell evolution earlier. In this thunderstorm the Doppler typical of mesocyclone circulations). radial velocity patterns are not as clear as before, though In Fig. 18 cross sections of Cells 2 and 3 are presented at strong shear is also present. At 3:18Z Cell 2 is shielding the the time of maximum surface wind speed at Zones 1 and 2, vision of Cell 3 (same line of sight from the radar) and given respectively. The tilting of the intense cores, and morphology that LMI operates on C-band, attenuation could be an issue — of cells resembles to some classical supercell features such as note that this also would contribute to increased uncertainty the weak echo region or the forward overhang (Browning, in radial velocity measurements. Cell 2 still presents a well 1964; Doswell and Burgess, 1993), suggesting the presence of defined shear pattern; in fact for several higher elevation intense updrafts, in addition to the shear mentioned above scans (including the 3° scan shown) the pattern is slightly indicating organized rotation at midlevels.

Fig. 13. Left: Zmax LMI radar reﬂectivity at 1:00 UTC; the arrow points to Cell 1. Right: infrared MSG satellite image. Cell 1 cloud top exhibits an expanding anvil, indicating strong updraft.

5. Summary and final remarks flash floods. The second part of the study, devoted specifically to total lightning analysis is presented in a companion paper This study has presented the first part of an analysis of the (Pineda et al., this issue). The synoptic and mesoscale 2nd November 2008 severe weather event that took place on environment of the event was characterized by a relatively the southern coastal part of Catalonia, including surface low CAPE but moderately high shear environment, as some damaging winds, hail, and also heavy rainfall and subsequent previous cases in Catalonia and also typical of other severe

Fig. 14. Base level (0.6°) PPI scans from the LMI radar showing radar reﬂectivity (dBZ) (top row) and radial velocity (m s− 1) (bottom row) at the time of maximum ground damage over Zone 1 (black arrow). Range circles are plotted at 20 km intervals. The 2:54Z radar reﬂectivity panel indicates the direction and range of the corresponding cross section shown in Fig. 18.

Fig. 15. As Fig. 14 but for 3.0° PPI scans (note that there is approximately a 2 minute lag between base level and 3.0° scans). weather events described in the cold-season in the UK model, including supercell composite parameter or upslope (Clarks, 2009); additional insight has been obtained from moisture ﬂux which provided good guidance about the examining a number of derived ﬁelds from the GFS NWP location and timing of severe weather and heavy rainfall

Fig. 16. Base level (0.6°) PPI scans from the LMI radar showing radar reﬂectivity (dBZ) (top row) and radial velocity (m s− 1) (bottom row) at the time of maximum ground damage over Zone 2 (black arrow). Range circles are plotted at 20 km intervals. The 3:24Z radar reﬂectivity panel indicates the direction and range of the corresponding cross section shown in Fig. 18.

Fig. 17. As Fig. 16 but for 3.0° PPI scans (note that there is approximately a 2 minute lag between base level and 3.0° scans).

Fig. 18. Radar cross-sections of reﬂectivity (dBZ) for Cell 2 (top panel, azimuth 90°, 40 km range) and Cell 3 (bottom panel, azimuth 56°, range 72 km) at the time of maximum ground damage at Zones 1 and 2, respectively. Directions of each cross section over the horizontal plane are indicated in Figs. 16 and 14. Horizontal and vertical axis units are in km.

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