Hurricane-like storm causes flooding in the mediterranean, october 2021
In the leadup to the COP26 climate conference, northern Africa and southern Italy have been experiencing first-hand the impacts of the changing climate, providing a glimpse of what may be to come.
From 24-25 October 2021 a tropical-like cyclone, named ‘Medicane Apollo’, formed in the Mediterranean and caused significant flooding in Sicily, southern Italy, Algeria, Tunisia, and Libya (1, EUMETSAT, 2021).
Medicane Apollo was responsible for at least 10 reported fatalities due to the flash floods caused by intense rainfall, which produced up to 440.2mm of rainfall in 24 hours in Fabrizia, Calabria (2, Severe Weather, 2021).
Figure 1: Video showing daily rainfall (in mm) between 24 October and 2 November 2021 over the Mediterranean along with the estimated tracking of Medicane Apollo. (Data source: NASA PPM, 2021; medicane track from (2), Severe Weather, 2021; video produced by JBA Risk Management Limited).
What is a medicane?
‘Medicane’ is a portmanteau of ‘Mediterranean’ and ‘hurricane’, a quasi-official term to represent cyclonic storms formed in the Mediterranean that have hurricane-like characteristics (3, González‐Alemán et al, 2019). They mostly form in the Ionian and Balearic seas (2, Severe Weather, 2021; 4, Columbia Climate School, 2017), as shown in Figure 2.
Figure 2: (a) Map of typical tropical cyclone locations and different geographical naming conventions; (b) focused map of the Mediterranean, with locations of typical medicane formation depicted by the orange symbols.
While tropical storms like hurricanes require a minimum sea surface temperature of 26°C for their development, medicanes can form over sea surfaces with temperatures below this threshold. Medicanes are most likely to form during the autumn and winter months, when strong temperature gradients exist and atmospheric instability is driven by cold air flowing across relatively milder seas.
Similar to tropical storms, the fuel for a medicane is provided by enormous quantities of moisture evaporating from the warm sea surface. The temperature difference between the air and the water creates unstable conditions that result in the formation of a low-pressure system.
The rising moist air produces deep convective clouds (cumulonimbus clouds) that generates thunderstorms and heavy rainfall. Surrounding air rushes in to replace the air ‘lost’ near the surface which continuously feeds the weather system. If the wind direction with height remains uniform the system can grow and develop into a large storm.
As this process continues, convective activity releases large quantities of heat that transforms the phenomenon into a warm core system (5, WMO, 2020; 6, Network Meteorology, 2021). For more information on hurricane formation, watch NOAA’s video.
Medicanes can be identified from satellite imagery using criteria based on their structure, size and lifetime; they can also be spotted by their vast cloud cover and symmetric shape around a clearly visible cyclone eye (7, Nastos et al., 2015).
Based on these criteria, 65 medicanes occurred between 1947 and 2014 (7, Nastos et al., 2015). Medicanes most commonly form between September and January as waters are relatively warmer during these months, favouring the development of low-pressure systems.
Maximum sustained wind speeds of historical medicanes range between 47 and 180 km/h (29-112 mph) (7, Nastos et al., 2015), which demonstrates that the most powerful medicanes can reach the equivalent of a category 3 hurricane on the Saffir-Simpson scale (see Table 1).
Table 1: Saffir-Simpson hurricane wind scale showing maximum sustained wind speed per category.
Medicane Apollo has gained historical significance as it is the first medicane event officially recognized by regional meteorological institutions, who have collectively come up with a “storm naming” project consisting of a list of names that can be used until 31 August 2022 (26, Meteo Aeronautica, 2021), similar to the North Atlantic hurricane naming system.
The “storm naming” project has helped to raise awareness of the importance of recognising such catastrophic storm events as abnormal and destructive, both regionally and globally.
Impacts of Medicane Apollo
Figure 3 shows the highest recorded rainfall (mm) within a 24-hour period during the event in the central Mediterranean.
Figure 3: Map showing highest recorded rainfall (in mm) in a 24-hour period during the event at various locations across Sicily, Catania and Tunisia. The shaded areas show the spatial distribution of rainfall over a 24-hour period between 24/10/2021 (02:32) and 25/10/2021 (02:32).
Sicily
Emergency authorities issued a red alert warning for parts of Sicily and Calabria, southern Italy, as heavy rainfall from Medicane Apollo produced flash floods which inundated populated regions (2, Severe Weather, 2021).
Eastern Sicily experienced the highest levels of rainfall, with a total of 520mm reported at Linguaglossa, Catania, from 24–26 October (2, Severe Weather, 2021). On 24 October, heavy downpours produced more than 300 mm of rain near Catania, which is nearly half the average annual rainfall for the island (8, FloodList, 2021; 9, Nature Italy, 2021).
Two fatalities were reported in Catania as vehicles were swept away by the flood water (10, BBC, 2021).
Over 300mm of rainfall was reported in Syracuse (11, Migliore, 2021), with 279.8mm recorded at Lentini on 25 October (8, FloodList, 2021). Part of the hospital was flooded in Avola city, in the province of Syracuse (11, Migliore, 2021).
Calabria, southern Italy
In Calabria, a reported 440.2mm of rainfall was reported in Fabrizia, which is more than 4 times the monthly average for October (2, Korosec, 2021; 12, World Weather Online 2021). Rainfall totals exceeding 300mm were also reported at Mongiana, Seguono Chiaravalle Centrale and Antonimina Canolo Nuovo in the Calabria region.
Algiers, Algeria
More than 100 properties were flooded in Algeria, following heavy rains which started on 23 October (8, FloodList, 2021). Algiers, Boumerdes, Chlef and Tizi Ouzou were some of the worst hit provinces.
Algiers city received more than 140mm of rain in 24 hours from 23–24 October (8, FloodList, 2021). In Ain Benian, 246mm of rain was reported, which is more than five times the average rainfall for October (13, MKWeather, 2021).
Two fatalities were reported in south-west Algiers, where dozens of people were rescued following heavy rains (14, The Mahgreb Times, 2021).
Tunisia
Heavy rainfall in Tunisia from 23–24 October produced a reported 168mm in Ras Jebel and 136mm in Sidi Thabet in the north of the country (8, FloodList, 2021). Three fatalities were recorded in Tunisia. In Thala, northwest Tunisia, two fatalities were reported, whilst another fatality was reported in Borj Chakir, near the capital Tunis (15, SOTT, 2021).
Libya
Flash floods associated with heavy rainfall from Medicane Apollo also affected hundreds of people in east Libya, with Benghazi and Marj districts the worst hit (16, OCHA Libya, 2021).
Notable historical events
Research by Bakkensen (17, Bakkensen, 2017) estimates historical medicane losses across the entire Mediterranean region and concludes that Italy is the country with the highest chance of a medicane making landfall (0.92 landfalls per year) as well as the largest expected average annual losses (USD $33 million).
These significant modelled annual losses are driven in part by the high frequency of historical events, as well as high value property and assets.
In contrast, Bakkensen’s research estimates that typical damages from medicanes making landfall in Africa are expected to be around five times lower than those in Europe, mostly due to the smaller average capital and socioeconomic differences.
Table 2: Historical events and reported losses for medicane events in the Mediterranean.
Future medicanes and a warming climate
Medicane Apollo’s formation in the run up to the COP climate summit provides a timely reminder.
Climate model projections suggest a decrease in the frequency of medicanes, but an increase in their intensity (27, Cavicchia et al., 2021; 28, Romera et al., 2017; 29, Walsh et al., 2013). Future medicanes are predicted to last longer and produce more intense precipitation, which poses a significant flood hazard to populated regions around the Mediterranean coast (3, González-Alemán et al., 2021).
As sea surface temperatures increase in the Mediterranean under a warming climate, this amplifies the potential intensity of medicanes. In turn, future medicanes will also have the potential to generate higher and more prolonged surges on Mediterranean coastlines (30, Scicchitano et al., 2021).
The impacts of climate warming are becoming more prevalent in the Mediterranean region. In Italy, the number of extreme weather events have increased from 380 in 2010 to 1,499 in 2020 (9, Nature Italy, 2021). In August 2021, the highest European temperature of 48.8°C was recorded in Syracuse, Sicily (31, The Guardian, 2021), whilst severe rainfall in Genoa, north-west Italy, broke the European 12-hour rainfall record when 742mm of rainfall was recorded in 12 hours on 4 October 2021 in Rossiglione (32, CNN, 2021).
Prior to the formation of Medicane Apollo, sea surface temperatures in the Aegean and Ionian Seas were 3°C and 2°C higher than average respectively (31, The Guardian, 2021).
Recent modelling of medicane response under an intermediate RCP4.5 scenario suggests that these events may develop more robust hurricane-like structures and are likely to produce stronger winds (3, González-Alemán et al., 2021). More extreme warming under stronger emissions scenarios (RCP8.5) would increase the temperature of the Mediterranean Sea further and therefore augment the potential hazard of future medicanes.
Densely populated cities along the coast of southern Europe and north Africa and on Mediterranean islands are at the greatest risk of flooding associated with future medicanes. Vulnerability to flood risk may be exacerbated by poorly maintained infrastructure and by urban development, particularly in north Africa (15, SOTT, 2021).
It’s vital that organisations act now in response to flood risk. We offer flood mapping and probabilistic flood modelling worldwide, including for Italy, Algeria, Tunisia and Libya, which provides flood risk insights at any location globally. This can help re/insurers, financial organisations, and the International Development sector to better understand and manage flood risk.
To find out more about our flood data and how it can help you, get in touch with the team.
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References
(1) https://www.eumetsat.int/multiple-severe-rain-events-mediterranean-africa
(2) https://www.severe-weather.eu/europe-weather/medicane-tropical-cyclone-sicily-italy-malta-flooding-mediterranean-mk/.
(3) https://doi.org/10.1029/2018GL081253
(4) https://news.climate.columbia.edu/2017/11/21/what-we-know-about-medicanes-hurricane-like-storms-in-the-mediterranean/
(5) https://public.wmo.int/en/media/news/medicane-hits-greece
(6) https://www.meteorologiaenred.com/en/medicane.html
(7) https://cest2015.gnest.org/papers/cest2015_00407_oral_paper.pdf
(8) https://floodlist.com/africa/algeria-tunisia-italy-medicane-floods-october-2021
(9) https://doi.org/10.1038/d43978-021-00136-0 (10) https://www.bbc.co.uk/news/world-europe-59048809
(11) https://www.3bmeteo.com/giornale-meteo/meteo--uragano-apollo--medicane--si-abbatte-sulla-sicilia--maltempo-di-pioggia-e-vento--alluvione-e-citt--isolate--la-situazione-con-foto-e-video-532122
(12) https://www.worldweatheronline.com/fabrizia-weather-averages/calabria/it.aspx
(13) https://mkweather.com/7-dead-after-a-devastating-medicane-in-algeria-tunisia-and-italy-320-mm-of-rain-in-linguaglossa-sicily-246-mm-in-ain-benian-algeria-and-136-mm-in-kalaat-andalous-ariana-tunisia/
(14) https://themaghrebtimes.com/floods-in-algeria-the-toll-is-growing/
(15) https://www.sott.net/article/459914-Three-killed-in-Tunisia-flash-floods?utm_source=rss&utm_medium=MINT+Social&utm_campaign=RSS
(16) https://www.unocha.org/libya
(17) http://www.laurabakkensen.com/wp-content/uploads/2016/01/Medicanes_11516.pdf
(18) https://doi.org/10.1002/j.1477-8696.1970.tb04128.x
(19) https://dbpedia.org/page/Cyclone_Qendresa
(20) http://thoughtleadership.aon.com/Documents/20171207-ab-analytics-if-november-global-recap.pdf
(21) https://floodlist.com/europe/greece-medicane-zorba-september-2018
(22) http://thoughtleadership.aon.com/Documents/20181009-ab-analytics-if-sept-global-recap.pdf
(23) https://apnews.com/article/dfddd2fd48384414a4f66eba6fd94609
(24) https://www.wunderground.com/cat6/Tropical-Storm-Medicane-Hits-Greece
(25) http://geerassociation.org/administrator/components/com_geer_reports/geerfiles/Medicane%20Ianos%20GEER%20Report.pdf
(26) http://www.meteoam.it/news/storm-naming-laeronautica-militare-nomina-le-perturbazioni-cicloniche-piu-intense
(27) https://doi.org/10.1175/JCLI-D-14-00339.1
(28) https://doi.org/10.1016/j.gloplacha.2016.10.008
(29) https://doi.org/10.1007/s00382-013-1723-y
(30) https://doi.org/10.1016/j.margeo.2021.106556
(31) https://www.theguardian.com/world/2021/oct/27/southern-italy-braced-for-rare-mediterranean-hurricane
(32) https://edition.cnn.com/2021/10/06/weather/italy-flood-oman-climate-change/index.html
