VOLUME 143 MONTHLY WEATHER REVIEW MARCH 2015

Tornadoes in Romania

BOGDAN ANTONESCU Centre for Atmospheric Science, School of Earth, Atmospheric and Environmental Sciences, University of Manchester, Manchester, United Kingdom

AURORA BELL Bureau of Meteorology, Melbourne, Victoria, Australia

(Manuscript received 2 June 2014, in final form 23 September 2014)

ABSTRACT

The first tornado climatology for Romania is presented based on datasets attained from three periods between 1822 and 2013. The historical period (1822–1944) contains 33 tornado reports originating from historical newspaper archives and publications of the Romanian Meteorological Institute. Evidence of tor- nado observations in Romania before the nineteenth century is found in the representation of tornadoes in the Romania folk mythology. The socialist period (1945–89) contains only seven tornado reports, likely be- cause during this period it was believed that tornadoes did not occur in Romania. The recent period (1990– 2013) contains 89 tornado reports that came from mass-media sources and eyewitness reports. Of the 129 tornadoes from the Romanian tornado database, 98 were reported between May and July with a peak in May (36 reports). Most of the tornadoes (28 reports) occurred during the afternoon hours 1500–1659 local time. Tornadoes were more frequently reported over eastern Romania compared with other regions of the country, 2 2 with a maximum over southeastern Romania [0.37–0.45 (105 km2) 1 yr 1].

1. Introduction the average annual number of tornadoes and waterspouts 2 in Europe is 483, representing 4.8 (105 km2) 1.Bycom- Tornado climatologies are important for understanding parison, the average annual number of tornadoes (no the formation and characteristics of severe convective waterspouts) in the United States between 2006 and 2013 storms, and also for better quantifying the risks that tor- 2 was 1228, representing 12.5 (105 km2) 1, based on the nadoes pose. The reported frequencies of tornadoes are, in National Oceanic and Atmospheric Administration pub- general, lower in Europe compared to the United States. In lication Storm Data (e.g., Smith et al. 2012; Thompson his study on tornadoes and waterspouts in Europe, Alfred et al. 2012). Although the threat is apparently smaller in Wegener estimated that at least 100 tornadoes occur each Europe compared with the United States, the true mag- year in Europe (Wegener 1917). More recently, Dotzek nitude of the tornado threat in Europe is not known be- (2003) estimated that 329 tornadoes and waterspouts are cause of the lack of assembled datasets. Despite their observed each year in Europe, based on a survey among importance, it was only recently that some of the Euro- the participants of the Second European Conference on pean countries started a systematic documentation of Severe Storms. Groenemeijer and Kühne (2014) showed, tornado events and developed tornado climatologies. based on the data from the European Severe Weather Tornado climatologies have been published for 14 (32%) Database (Dotzek et al. 2009) between 2006 and 2013, that of the 44 countries that have their capital city within Eu- rope, covering approximately 2 958 988 km2 (30%) of the

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Publisher’s Note: This article was revised on 25 August 2015 to Corresponding author address: Dr. Bogdan Antonescu, Centre include the CCBY license that was missing when originally published. for Atmospheric Science, School of Earth, Atmospheric and En- vironmental Sciences, University of Manchester, Simon Building, Oxford Road, Manchester M13 9PL, United Kingdom. This article is licensed under a Creative Commons E-mail: [email protected] Attribution 4.0 license.

DOI: 10.1175/MWR-D-14-00181.1

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FIG. 1. The spatial distribution of tornado climatologies in Europe. The countries for which tornado climatologies have been published (Table 1) are represented in green, and the climatologies for eastern Europe are labeled. Romania is represented in orange.

European surface area (9 930 054 km2). The European and 16 tornadoes were reported for each century up to tornado climatologies mainly focused on northern, south- 1800. A maximum in the number of tornado reports was ern, and western Europe and, to a lesser extent, on eastern observed between 1931 and 1940 (44 tornado reports) and Europe (e.g., Szilárd 2007; Brázdil et al. 2012; Simeonov another maximum in 2001–10 (56 tornado reports). The et al. 2013)(Fig. 1 and Table 1). recent increase in the number of tornado reports was at- For Hungary, Szilárd (2007) developed a synoptic tributed to the ‘‘availability of relevant sources as well as climatology of damaging tornadoes (defined as torna- increased social awareness and advances in communica- does producing any type of damage) reported between tion technology’’ (Brázdil et al. 2012, p. 193). 1990 and 2001. Before 1990, damaging tornadoes were Simeonov et al. (2013) analyzed the tornado reports estimated to occur less than once in a decade. Between for Bulgaria and showed that 57 tornadoes occurred in 1990 and 2001, 36 tornadoes were reported, of which 18 51 days between 1956 and 2010. The majority of torna- were damaging tornadoes. The increase in the number does were reported after 1990 (45 reports). For a period of tornado reports after 1990 was attributed to an in- of 35 yr between 1956 and 1990, only 12 tornadoes were crease of vulnerability of society and industry, an in- reported in Bulgaria. During this period ‘‘most people in crease in the public awareness and also to a ‘‘possible Bulgaria thought that tornadoes were exotic and not intensification of convective activity (among [those] typical events for [the] country’’ (Simeonov et al. 2013, years were record hot summers)’’ (Szilárd 2007, p. 264). p. 62). The increase in the number of tornadoes after Brázdil et al. (2012) analyzed the spatial and temporal 1990 was attributed to the development of communi- distribution of tornadoes in Czech land (recent Czech cations and the Internet, which made available the tor- Republic) from 1119 to 2010. During this, period 307 tor- nado reports collected by amateurs. nadoes occurred in 264 tornado days (defined as the days The aim of this article is contribute to the climatology in which a least one tornado was reported). Before 1500 A. of tornadoes in Europe by presenting the first tornado D., a total of four tornadoes were reported, and between 11 climatology for Romania, a country with a long history

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TABLE 1. Climatologies of tornadoes for European regions. The European regions are based on the definition from the United Nations Statistics Division (available online at http://unstats.un.org/unsd/methods/m49/m49regin.htm). The tornado climatology for Turkey was also included since Turkey is a contiguous transcontinental country, located in western Asia and southeastern Europe.

Region Country Study Study period Northern Europe Finland Rauhala et al. (2012) 1796–2007 Sweden Peterson (2000) 1725–1996 Lithuania Marcinoniene (2003) 1950–2002 Estonia Tooming (2002) 1795–2001 Ireland Tyrrell (2003) 1950–2001 United Kingdom Holden and Wright (2004) 1091–1999 Western Europe Germany Dotzek (2001) 1587–1999 Austria Holzer (2001) 1910–99 France Paul (2001) 1680–1999 Southern Europe Italy Peterson (1998) 1456–1992 Giaiotti et al. (2007) 1991–99 Spain Gayà (2011) 1825–2009 Portugal Leitão (2003) 1936–2002 Greece Matsangouras et al. (2014) 1709–2012 Turkey Kahraman and Markowski (2014) 1818–2013 Eastern Europe Czech Republic Setvák et al. (2003) 1119–2002 Brázdil et al. (2012) 1119–2010 Hungary Szilárd (2007) 1996–2001 Bulgaria Simeonov et al. (2013) 1956–2010 of meteorological observations in eastern Europe (the historical database, starts in 1822 and ends in 1944 when Romanian Meteorological Institute was founded in 1884) Romania became a socialist country (section 2a). The (Fig. 1). This article is structured as follows. Section 2 second period contains only seven tornado reports for describes the Romanian tornado database. The spatial an interval of 55 yr between 1945 and 1989. The third distribution of tornado reports is described in section 3. period contains the tornado reports between 1990 and The monthly and diurnal distributions of tornado reports 2013, the period during which the RNMA has been are discussed in sections 4 and 5, respectively. Finally, collecting and analyzing tornadoes reports in Romania section 6 summarizes the results of this paper. (section 2c). a. Historical tornado reports 2. Data The first tornado report in Romania is from the be- The definition of a tornado used in this article has been ginning of the nineteenth century, but tornadoes have adopted from the Glossary of Meteorology (Glickman been observed before, as is shown by the Romanian folk 2000). Thus, a tornado is defined as ‘‘a violently rotating mythology related to the figure of the ‘‘dragon’’ (balaur column of air, in contact with the ground, either pendant in Romanian) and the ‘‘sorcerer’’ (solomonar in Ro- from a cumuliform cloud or underneath a cumuliform manian). For the folk mentality, the dragon is the cloud, and often (but not always) visible as a funnel cloud’’ Principal of Disorder, which disturbs the order of nature (Glickman 2000, p. 781). In this article, the definition was and human communities by bringing thunderstorms and extended by considering all the waterspouts that hit the hail. The ‘‘solomonar,’’1 the Principle of Order, is land as tornadoes, consistent with the tornado definitions a sorcerer that has the power to control the weather used in other European countries (e.g., Rauhala elements and to subdue the dragon (Ois¸teanu 2013). In et al. 2012). This definition of a tornado was used by the the folklore of other countries, high winds and severe Romanian National Meteorological Administration storms also had supernatural representations or were (RNMA) since 2005. The intensity of all tornadoes in the interpreted as divine judgment [e.g., Jankovic (2000), for Romanian tornado database was assessed following the United Kingdom]. We conjecture that tornadoes have approach of Rauhala et al. (2012), based on (i) the Fujita been represented in the Romanian folk mythology as scale [F scale; Fujita (1981)] and (ii) guidance for as- signing tornado damage to buildings [Table 4 in Minor et al. (1977); appendix C in Bunting and Smith (1993)]. 1 The term is quite recent and is documented approximately The climatology of tornadoes in Romania was divided between 1650 and 1750 in Transylvania, central Romania into three periods. The first period, comprising the (Ois¸teanu 2013).

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FIG. 2. The topography of Romania and the spatial distribution of the folklore sources in which the tornadoes are mentioned as balauri (yellow circles). The major cities in Romania (with populations greater than 280 000) are represented by the black circles. Other cities referenced in this article are represented by white circles.

‘‘balauri’’ [‘‘ale,’’ or ‘‘hale’’ in southern Romania; southeastern Romania, no folklore sources could be Has¸deu (1887)]. The description of the dragons varies identified in which tornadoes are represented as dragons,2 from one region to another, but with some common despite the fact that a large number of the tornadoes in the characteristics. Thus, the dragon has a long tail ‘‘swinging recent period are reported in this region. when it is up into the cloud’’ (representing the funnel The first historical report of a tornado in Romania is cloud) and ‘‘slapping with a loud noise when it is touching from 4 June 1822 and occurred in Banat (near Timis¸oara the ground’’ (representing the tornado itself); the in Fig. 2). The severe storm, described as a whirlwind, hit dragon’s head is either the head of a crocodile or the head several villages and destroyed houses and churches and of a horse (representing the anvil of the cumulonimbus uprooted or snapped large trees, the damages being cloud); the dragon’s breath ‘‘is so cold that [it] is freezing evaluated at approximately 90,0000 florins [approxi- the water in the clouds’’ thus producing large hail mately $1 million (U.S. dollars) in 2014] (Dudas¸ 2006, (sometimes associated with tornadic events); the dragon p. 45). Most of the historical tornado reports came from is also able to ‘‘lift people up into the clouds’’ (Marian newspaper archives. To find these reports, newspapers 1878a,b; Pamfile 1915, 1916; Gherman 1928; Rezus¸ 1972). between 18293 and 1944 were studied using archives Sometimes the dragon takes the form of a winged white from the Digital Library of Bucharest (http://www. horse, which the solomonar rides through the clouds dacoromanica.ro) and the Digital Library of the (Ionitxa 1982). These winged horses ridden by sorcerers with meteorological powers are also mentioned in Serbo- Croatian mythology [‘‘graboncijas dijak’’; Jagic(1877)]. 2 ‘‘Volbura’’ is another term used to described whirlwind events Thus, tornadoes were not unknown events in Romania over southeastern Romania (Gherman 1928), but this term is used in the folklore sources to describe dust whirls (i.e., dust devils) and before the nineteenth century, as shown by the geo- not tornadoes. graphical distribution of the folklore sources in which 3 The first Romanian newspapers, Albina Romaneasc^ a and the tornadoes are mentioned as balauri (Fig. 2). For Curierul Romanesc,^ were first published in 1829.

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Central University Library of Cluj-Napoca (http:// dspace.bcucluj.ro/). National (e.g., Adevarul , Albina Romaneasc^ a, Curierul Romanesc^ , Epoca, Scanteia)^ and local (e.g., Albina Carpatxilor, Clujul, Gazeta de Tran- silvania) newspapers were studied using keyword searches for ‘‘tromba’’ (from the French trombe or the Italian tromba word for tornado) [e.g., Hepites (1887) used the term ‘‘tromba’’ to describe the 9 June 1886 Bucharest tornado], ‘‘uragan/orcan’’ (from the French ouragan or the German orkan for strong windstorms) [e.g., Hepites (1904) used the term uragan to describe the 29 June 1904 Moscow tornado], ‘‘tornada’’ (tor- nado), and ‘‘vartej’’^ (whirlwind). This keyword search resulted in approximately 2690 archive entries, which were then analyzed individually to identify tornado events based on the information from the newspaper FIG. 3. The distribution of tornado reports per decade between 1822 and 2013. The first decade includes 1822–29 and the last de- article (e.g., description of an event and its damage, cade includes 2010–13. eyewitness reports, location, and time of occurrence). Thus, 16 tornado reports (48.5%) of the 33 reports from the historical dataset are from newspaper articles particular, local newspapers) published between 1822 and (Fig. 3). The most significant tornadic event retrieved 1944 were available for analysis. Compared with a tor- from the newspaper archives is a tornado ranked as nado damage surveys, a tornado report retrieved from a category 3 (F3) event on the Fujita scale that oc- a newspaper contains a limited description of the event. curred on 13 May 1912. The tornado killed six people Thiscouldresultinlocationandtimeerrors.Also,tor- and injured more than 50 others, and caused extensive nado reports were collected by the Meteorological In- damage to five villages near Dej, central Romania stitute between 1884 and 1915. In 1916, Romania declared (Fig. 2). war on Austria–Hungary, thus formally entering World Tornado reports were also collected from Annals of War I, and the Meteorological Institute ceased all activi- the Romanian Meteorological Institute (14 reports), ties due to shortage of staff. The activity of the Meteo- marginalia [2 reports; Dudas¸ (2006)], and memoirs rological Institute was fully restored in 1920, but without [1 report; Michelet (1916)]. The Annals, published be- any official publications until the 1950s. tween 1886 and 1915, contained monthly summaries of b. Tornado reports during socialist period meteorological data and descriptions, as well as case studies of significant weather events. The first case study For the socialist period (1945–89), only seven tornado of a tornado in Romania, describing the 9 June 1886 reports were included in the database (Fig. 3). Two re- tornado that hit Bucharest, was published in the second ports came from the monthly meteorological bulletin issue of the Annals (Hepites 1887). The tornado oc- published by the Meteorological Institute. In the 1960s, curred close to the Meteorological Institute, thus al- two tornadoes were documented in the meteorological lowing detailed observations. At least three houses were observers notebooks, but because they were considered completely destroyed, and one person was killed by the erroneous observations, they were not included in the tornado that occurred between 1700 and 1800 LT (1500– official reports. The keyword search in the digital 1600 UTC). At the Meteorological Institute, situated newspaper archives between 1945 and 1989, using the approximately 9 km from the area most affected by the same methodology as for the historical period, resulted tornado, the wind changed from easterly to northeast- in only two tornado reports. The lack of tornado reports 2 erly and reached a maximum speed of 15 m s 1 during during the socialist period can be a result of the fact that the passage of the storm, which also produced hail with in the 1970s and 1980s, the word tornado was forbidden in a diameter of 2 cm. A damage survey was conducted by the official meteorological reports and in the mass media S¸ tefan Hepites, the first director of the Meteorological reports, despite the previous observations of tornadoes in Institute, wherein the damages were estimated at Romania. During this period, the senior meteorologists 200,000 francs [approximately $800,000 (U.S. dollars) in considered that tornadoes do not occur in Romania be- 2014]. cause the country is situated too far north (approximately There are a series of limitations with the historical 458N), and ‘‘thus the Coriolis effect will not allow the tornado dataset. Thus, not all the newspapers (in formation of tornadoes,’’ which are ‘‘confined to the

Unauthenticated | Downloaded 10/03/21 08:57 PM UTC 694 MONTHLY WEATHER REVIEW VOLUME 143 tropics’’ (Lemon et al. 2003).4 All the tornadic events reports). The eyewitness reports were submitted by pro- during this period were described as high-wind events, fessional meteorologists (two reports, 2.2% of all recent thus not recognizing the threat of tornadoes. This situa- reports) and severe weather spotters (two reports, 2.2% tion is what Doswell (2003) described as a self-fulfilling of all recent reports). Radar and satellite data were an- prophecy: denying the existence of tornadoes in Romania alyzed for all the tornado reports after 2002 to confirm resulted in no record keeping for such events, and when that the radar imagery showed radar echoes or the sat- tornadoes were observed, they were not reported. A ellite imagery showed cloudiness during or after the time similar situation was described by Setvák et al. (2003) for of the event. Even with a verification system in place, the Czech Republic. Another source of tornado reports there are limitations to the correctness of the tornado for this period is the eyewitness reports received at the reporting. Thus, not all the recent tornado reports were Meteorological Institute after 2002. Thus, one report was well correlated with the cell locations from the radar data. included in the database based on the interview with the These differences were associated with locations errors eyewitness. (e.g., location of the nearest village was provided instead of the actual location of the tornado) and time errors c. Recent tornado reports (e.g., only an estimate of the actual time of the tornado After the fall of the Iron Curtain and the Romanian was provided). Revolution in 1989, there was no formal recognition that Altogether, 129 tornadoes that occurred on 112 days tornadoes can occur in Romania. This situation changed have been reported in Romania between 1822 and 2013. in August 2002 when an F31 long-track tornado cross- The majority of the tornadoes occurred over land (121 ing through southeastern Romania was responsible for reports) and eight tornadoes occurred first over water at least three fatalities and the destruction of 33 houses and then hit the land. Certainly, this dataset is in- mainly in the village of Fac aeni (Lemon et al. 2003). complete, as shown for example by the low number of Although this was not the first F3 tornado documented tornado reports during the socialist period. The Roma- in Romania, it was the first F31 tornado whose parent nian tornado dataset is clearly dominated by recent storm circulation was observed with the new Romanian events, with an increase in the number of reports after Doppler radar network installed in 2002. The radar net- the year 2000 (Fig. 3). This increase in the number of work comprised five Weather Surveillance Radar-1998 tornado reports was observed in other European coun- Doppler (WSR-98D) S-band radars and three existing tries, too. For example, for Finland, Rauhala et al. C-band radars (Ioana et al. 2004). The data provided by the (2012) showed an increase from 50 tornado reports be- Romanian radar network and the radar-data algorithms tween 1990 and 1999, to 130 reports between 2000 and for mesocyclones (Mitchell et al. 1998) and tornado 2007. For Romania, the recent increase in the number of detection (Stumpf et al. 1998) were successfully used in tornado reports can be attributed to 2005 to issue the first tornado warning in Romania 1) increased public awareness after the Fac aeni F31 (Teittinen and Schultz 2008). After 2005, a systematic tornado in 2002; documentation and analysis of tornado reports was 2) implementation of the WSR-98D radar network in started at the RNMA with the aim of developing a tor- 2002 (Ioana et al. 2004) helped in defining tornado nado database for Romania. locations considerably, especially in underpopu- Of the 89 tornadoes reported between 1990 and 2013, lated areas, by detecting the larger circulation 85 reports were obtained from mass-media sources and pattern in which the tornado was embedded (i.e., 4 reports were eyewitness reports submitted to the the mesocyclone); RNMA. A mass-media report was confirmed if (i) 3) a rapid increase in cellular telephone subscriptions a photo or a video of the tornado was available (40 re- per 100 inhabitants from 11.2 in 2000 to 105.0 in 2012, ports, 45.0% of all recent reports), (ii) a photo or a video along with a rapid increase in the percentage of showing typically tornado damage and interviews with individuals using the Internet from 3.7 in 2000 to 50.0 the credible eyewitnesses were available (26 reports, in 2012;5 29.2%), or (iii) a damage survey or a cases study was 4) volunteer severe weather spotters, some of them conducted by the RNMA (19 reports, 21.3% of all recent trained by the RNMA (e.g., the Association for

4 This explanation can also result from the confusion between the 5 Source is the World Telecommunication/Information and word ‘‘uragan’’ used to describe tornadoes in the historical data- Communication Technologies Indicators Database (2013) (avail- base and the use of the word in modern Romanian to describe able online at http://www.itu.int/en/ITU-D/Statistics/Pages/stat/ tropical cyclones. default.aspx).

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Monitoring Severe Weather Phenomena was founded in 2010); and 5) the ‘‘Twister effect’’ hypothesized by Rauhala et al. (2012) in which the movie Twister (released in 1996) and documentary reality television series about tornadoes (e.g., Storm Chasers that premiered in 2007) resulted in an increased awareness among the public about tornadoes.

3. Spatial distribution

The spatial distribution of tornadoes reports in Romania is shown in Fig. 4. The distribution of tornado reports during the historical period reflects the avail- ability of documentary sources rather than the true distribution. Thus, the majority of tornadoes (29 reports representing 87.9% of all historical reports) were re- ported over southern and eastern Romania, a region that between 1881 and 1913 was the Romanian King- dom. The region of Romania bounded to the east and south by the Carpathian Mountain Range was a part of the Austro–Hungarian Empire before 1918, and no of- ficial reports for this region were available before 1920 (Fig. 4a). Figure 5 shows the distribution of all tornado reports between 1822 and 2013 by F scale, in which the F-scale estimate is the minimum that can be retrieved from the description of the event. From the 23 historical reports for which an estimation on the F scale was possible, 11 reports were for weak tornadoes [F0 or F1; Hales (1988)] and 12 reports were for significant tornadoes (F2 or F3). The large percentage of significant tornadoes during the historical period compared with the other periods is be- cause strong tornadoes have a large impact on society and are therefore more likely to be reported than weak tor- nadoes (Brooks and Doswell 2001; Verbout et al. 2006). During the socialist period, the annual average number 2 2 of tornado reports decreased from 0.44 (105 km2) 1 (yr) 1 2 2 between 1879 and 1913 to 0.06 (105 km2) 1 (yr) 1 be- tween 1945 and 1989. All the tornadoes reported during the socialist period, with one exception (the 12 June 1961 tornado from Cluj), occurred over eastern and southern Romania (Fig. 4b). The lack of tornado reports is an artifact of the socialist period and not the result of cli- matological factors. For example, Iliescu (1989) showed, based on cloud-to-ground (CG) lightning data between

1966 and 1980, gathered using CG lightning counters, FIG. 4. Spatial distribution of (a) historical tornado reports (33 that the annual average number of thunderstorm days reports between 1822 and 1944), (b) tornado reports during the (days in which at least 15 CG lightning flashes were socialist period (7 reports between 1945 and 1989), and (c) recent detected) varies from 35 to 40 thunderstorm days over tornado reports (89 reports between 1990 and 2013) in Romania. most parts of Romania to 25–30 days over southeastern Tornadoes were classified according to their intensity on the F scale for weak tornadoes (F0 or F1) (yellow) and significant tornadoes Romania [Fig. 21 in Iliescu (1989), p. 87]. Geicu and (F2 and F3) (red). Tornadoes for which an estimation of the in- Candea^ (2008), using data from the Romanian surface tensity was not possible are represented in blue.

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shows that the average number of tornadoes is between 2 2 0.30 and 0.45 (105 km2) 1 (yr) 1 [approximately 1.5–2.25 2 (105 km2) 1 every 5 yr] over northeastern and south- 2 2 eastern Romania, and is lower than 0.22 (105 km2) 1 (yr) 1 (approximately 1.1 tornadoes every 5 yr) over most of Romania (Fig. 6a). The high number of tornadoes over northeastern Romania can be attributed to the population density across this region, with high population density resulting in more tornadoes being reported. Figure 6b shows, based on data from the Romania National Institute of Statistics, that the population density in 2003 over FIG. 5. Number of tornado reports during the historical period northeastern Romania was greater than 100 people per (1822–1944) (light gray, bar chart), the socialist period (1945–89) kilometer squared. The high number of tornadoes over (dark gray, bar chart), and the recent period (1990–2013) (solid line) based on estimated intensity on the F scale. southeastern Romania (maximum over Romania) can- not be entirely attributed to the population density. Compared with northeastern Romania, the population observation network collected between 1961 and 2000, density over southeastern Romania is lower (70–80 showed that the annual average number of thunder- people per kilometer squared) with fewer urban areas, storm days over Romania varies from 30 to 40 days. derived from the 2002–03 Moderate Resolution Imaging Thus, the annual average number of thunderstorm days Spectroradiometer (MODIS) data at 1-km grid spacing is not lower during the socialist period compared with (Schneider et al. 2003)(Fig. 6b). the average between 1961 and 2010. The high number of tornadoes over southeastern For the recent period, the annual average number of Romania can be attributed to the mesoscale environ- tornado reports increased compared with the previous ments over this region that are more favorable for tor- 2 2 periods to 1.55 (105 km2) 1 (yr) 1 between 1990 and nadoes compared with other regions. Brooks et al. 2013. The tornado reports are most frequent for the low (2003b) used the National Centers for Environmental elevations over southern and eastern Romania with Prediction–National Center for Atmospheric Research a maximum over southeastern Romania (Fig. 4c). From (NCEP–NCAR) global reanalysis dataset (Kalnay et al. the 41 recent reports for which an estimate of the F scale 1996) for the years between 1997 and 1999 to obtain was possible, 68.3% (28 reports) were for F0 tornadoes, vertical profiles that resemble radiosonde profiles (Lee 24.4% (10 reports) were for F1 tornadoes, and 7.3% 2002). The profiles were used as proximity soundings to (3 reports) for F2 or F3 (Fig. 5). The small percentage of develop relationships between the environmental vari- significant tornadoes during the recent period can be at- ables (e.g., CAPE, 0–6-km shear, 0–1-km shear, and 2–4-km tributed to a more efficient collection of tornado reports lapse rate) and severe convective storms in the United (particular those for weak tornadoes) and to an increased States. These relationships were then applied to make awareness among the public. Similarly, Rauhala et al. estimates of the distribution of favorable severe con- (2012) showed that the 29% of the tornado reports in vective storms and tornado environments over Europe. Finland between 1796 and 1996 were for significant tor- For Romania, the average number of days with favor- nadoes, and only 4% of the reports between 1997 and able tornado environments is between 4.5 and 6.0 over 2007 were for significant tornadoes. southeastern Romania and is lower than 3.0 days over Figure 6a shows the average number of tornadoes per most of Romania (Fig. 16 in Brooks et al. 2003b, p. 89). 105 kilometers squared per year based on the tornado Thus, the results from the present study are consistent reports between 1822 and 2013 using kernel density es- with the results obtained by Brooks et al. (2003b) for the timation (KDE). The KDE for a spatial point pattern distribution of favorable tornado environments over (i.e., tornado locations) assumes that the spatial pattern Romania. has densities at every location, rather than only at the locations where the events were reported (e.g., Dixon 4. Monthly distribution et al. 2011; Brooks et al. 2003a). In this article, a Gaussian kernel with a bandwidth of 50 km (compa- From the 126 tornadoes reported in Romania be- rable with the area for which the RNMA issues severe tween 1822 and 2013 containing information on the oc- weather warnings) was used. The 50-km KDE, calcu- currence month, 125 tornadoes were reported between lated on a 10-km output grid to produce a smooth map, March and September and one tornado was reported

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FIG. 6. (a) KDE analysis for the tornado reports in the recent dataset (1990–2013) showing 2 2 the annual average number of tornado reports [(105 km2) 1 yr 1, shaded according to the scale]. (b) Population density of Romanian counties (people per km2, shaded according to the scale) and the urban areas (blue) derived from the 2002–03 MODIS data at 1-km resolution (Schneider et al. 2003).

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FIG. 7. The percentage of the annual total of tornado reports (bar FIG. 8. The percentage of the daily total of tornado reports be- chart) and tornado days (solid line) occurring in each month be- tween 1822 and 2013 occurring in 2-h bins starting at the indicated tween 1822 and 2013. local time (e.g., 1500 LT indicates the period between 1500 and 1659 LT). during wintertime on 24 January 2006. The tornadoes occurred on 110 tornado days, defined as the days in Giaiotti et al. (2007) for Italy; Matsangouras et al. (2014) which at least one tornado was reported. The earliest for Greece]. start of the tornado season in Romania occurred on 29 ^ March 2006, when a tornado was reported over Targu- 5. Diurnal distribution Jiu (southern Romania; Fig. 2), and the latest end of the tornado season occurred on 23 September 1913, when The diurnal distribution of tornadoes in Romania into a tornado was reported over Tuzla (eastern Romania; 2-h bins in local time (LT 5 UTC 1 2 h), is shown in Fig. 2). The majority of tornadoes have been observed Fig. 8. The diurnal distribution is based on 95 tornado during May–July, when 98 tornadoes (77.8% of the re- reports (75.4% of all reports) between 1822 and 2013 ports containing information on the occurrence month) that contained information on the occurrence time. The were reported in 83 days (75.5% of the tornado days) majority of tornadoes (88 reports, 92.6% of all cases) (Fig. 7). The peak month for tornado reports is May, were reported between 0900 and 2059 LT, with a peak in with 36 reports representing 28.6% of the reports con- the afternoon between 1500 and 1659 LT (28 reports, taining information on the occurrence month. The large 29.4% of all cases). The reporting of only seven torna- number of tornado reports includes a tornado outbreak does between 2100 and 0859 LT may be because of the from 7 May 2005, when eight tornadoes were reported difficulties associated with spotting tornadoes at night over southeastern Romania. The peak month for tor- (sunset is approximately at 2100 LT during June– nado days is June with 31 days representing 28.2% of all August) or because they occur when the public tends to tornado days (Fig. 7). be asleep (Ashley et al. 2008). The diurnal distribution of As in Romania, tornadoes in the neighboring coun- tornado reports in Romania is similar to those observed tries occur most frequently between May and August, in the neighboring countries. For Bulgaria, Simeonov with a peak in late spring or early summer (May–June) et al. (2013) showed that tornadoes tend to occur be- [Szilárd (2007) for Hungary; Simeonov et al. (2013) for tween 1400 and 1800 LT (80% of all reports) with a peak Bulgaria]. The peak occurs later in the summer (July– around 1600 LT. Tornadoes in Hungary occur most August) over western Europe [Holzer (2001) for Aus- frequently between 1500 and 1900 LT (72% of all re- tria; Dotzek (2001) for Germany; Paul (2001) for ports) (Szilárd 2007). France] and northern Europe [Tooming (2002) for Es- tonia; Marcinoniene (2003) for Lithuania; Rauhala et al. 6. Conclusions (2012) for Finland; Peterson (2000) for Sweden; Holden and Wright (2004) for the United Kingdom; Tyrrell This study summarizes the tornado climatology of (2003) for Ireland]. For southern Europe, the peak oc- Romania between 1822 and 2013 based on a dataset curs in late summer and autumn (August–October) comprising 129 tornadoes reported on 112 days. The [Gayà (2011) for Spain; Leitão (2003) for Portugal; tornado climatology was divided into three periods:

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(i) the historical period (1822–1944) during which 33 improving the manuscript. This work was initiated when tornadoes were reported, (ii) the socialist period (1945– both authors were at the Romanian National Meteoro- 89) containing only 7 reports, and (iii) the recent period logical Administration, and we thank all our colleagues (1990–2013) with 89 tornado reports. The increase in the in the Laboratory of Nowcasting Techniques and Severe number of reports during the recent period can be at- Weather Forecasting for their contributions to the de- tributed to increased public awareness (e.g., after the velopment of the Romanian tornado database. We also Fac aeni F31 tornado from 2002, or due to movies and thank Editor Pam Heinselman and anonymous re- documentary reality television series on tornadoes), in- viewers for their comments that improved our article. creased access to information and communication Partial funding for BA comes from Grant NE/H008225/1 technology (e.g., mobile phones, Internet), and volun- from the U.K. Natural Environment Research Council teer severe weather spotters. The main conclusions of (NERC) to the Tropopause Folding, Stratospheric In- the study are as follow. trusions and Deep Convection (TROSIAD) project at the University of Manchester and from an AXA Re- 1) The spatial distribution of tornado reports shows that search Fund postdoctoral grant. tornadoes are more frequently reported over eastern Romania, with a maximum over southeastern Ro- 2 REFERENCES mania [approximately 1.5–2.25 (105 km2) 1 every 5 yr]. We speculate that the large number of torna- Ashley, W. S., A. J. Krmenec, and R. 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