The 2014 Pentecost weekend storms in Europe were a series of intense supercells and MCSs affecting western and central Europe, which followed a heatwave in early June 2014, resulting from a Spanish plumesynoptic weather pattern.[2][3] The weekend saw repeated convective storm development across an arc from southwest France towards Paris and on towards Belgium and northwest Germany, where warm air masses interacted with cooler air and the frontal zone of a trough moving towards the continent from the Atlantic. Outbreaks of severe weather associated with this system spanned over 5 days from June 6 to June 11, with the worst damage occurring in the German state of North Rhine-Westphalia on 9 June,[4] where the storm was described as one of the most violent in decades by the German Weather Service (Deutscher Wetterdienst).[5] The responsible low pressure system is also referred to as storm "Ela" in some German media.
On June 4, a small low pressure system formed just south of Greenland and raced southeast the following day.[6] It deepened and expanded into a large trough and became almost stationary just off the coast of western Europe, roughly at the same latitude as France. Between the trough and a high pressure system over central Europe, a hot and moist airmass originating from northern Africa and the Mediterranean Sea made its way into western Europe.[7][8] These synoptic conditions are also referred to as a Spanish plume or as described in German as an "antizyklonale Südlage" (by the Free University of Berlin).[9][10] This airmass from the Mediterranean as well as Morocco and Sahara,[11] saw temperatures reach up to 38°C[12] and cause very high instability with Mixed Layer CAPE values exceeding 3000 J/kg. A strong jet over western Europe had also developed along the southeastern flank of the trough, creating strong windshear necessary for organization of thunderstorms into supercells and squall-lines. The broad nature of the trough with multiple centres and a wave pattern along the edges, as well as thermic surface lows caused areas of convergence which penetrated the already unstable atmosphere and enabled the formation of multiple rounds of severe thunderstorms.[7]
Only on June 10 and 11, the area of low pressure began moving again in a northeastward direction, before completely dissipating early on June 12.[13]
Heatwave
Europe temperature anomaly June 8–14, 2014
Over the weekend before Pentecost temperatures reached a new level for the first ten days of June and monthly records were broken in some areas of eastern France and southwestern Germany.
France
Across France the temperature widely exceeded 30°C, reaching over 35°C in the areas of the Massif Central and the south and east of the country.[14] The warmest regions were predicted to occur in the area from Lyon to Alsace.[15] With the French regions from the Pyrenees to the Paris Basin and on to Belgium seeing high temperatures, while warm air moved into the east of France and into Germany from the south.[16]Marisol Touraine, the French Minister of Social Affairs and Health activated the public information system in response to the heatwave.[17]
NOAA 48-hour airmass trajectory for Zurich 8 June 12.00 UTC at 3000 meters.
Switzerland
Switzerland saw high temperatures though not extreme or record breaking, temperatures were 30-34°C in the Rhine valley and Valais. Pilatus mountain above Lucerne witnessed a concentration in Saharan dust carried over in the air mass.[11] 9 June equalled the maximum recorded temperature in Sion at 36.2°C, the Swiss lowlands saw a high temperature of 35.5°C recorded in Basel.[18]
Germany
The warm airmass approached Germany from south-east along the Rhône valley and through the Belfort Gap, first in to the Upper Rhine Graben which saw especially warm temperatures. Another area of heat was focused in the Lower Franconian "heat island", where also temperatures of more than 37 degrees Celsius were measured.[19]
First severe activity started in southwestern France on June 6, where some straight-line wind damage occurred in association with thunderstorms.[20]
June 7
June 7 also remained relatively quiet except for a few storms in Belgium and in France which produced hail and once again damaging winds. A weak thunderstorm also produced a damaging F1 tornado in Ribeira, Spain.[20]
June 8
Storm activity ramped up significantly on June 8, when multiple strong supercells developed over northern France, Belgium and Germany. Severe winds and damaging hail occurred in these storms; hailstones up to 7.5cm fell in Lokeren, Belgium, and another supercell produced 9cm hail north of Paris. A wind gust of 105km/h (65mph) was measured in Magnanville.[20]
June 9
Lightning over western Europe 9 June 2014
June 9 saw the highest activity of the entire outbreak. The supercells over northern France from the previous day moved into the BeNeLux states during the overnight hours, continuing to produce large hail and strong winds. In Zeeland, Netherlands a 83km/h (51mph) gust was measured at the Tholen measuring station.[21] They would eventually reach northwestern Germany in the early morning, and merge into an MCS.
Meanwhile, new storms had fired over northern France and quickly grew upscale into a second MCS. By 8 am, two large clusters were active, one in northern France and one in northern Germany,[22] however, these systems would begin to weaken from that point in time, while moving northeast. New thunderstorms were already in progress directly behind the northern France MCS, some of which developed into discrete, intense supercells. One supercell in particular would pass directly over Paris while producing very large hail up to 10cm in diameter, causing significant damage in the city.[23] By 1 pm, the northern France MCS had already reached the Netherlands, and its outflow boundary caused new hail-producing supercells to form in Northrhine-Westfalia.[20] The MCS restrengthened again as well, causing severe winds, mainly in the Netherlands.
As time approached evening, the former discrete supercells over France had reached Belgium, where they grew upscale into a strong line of severe thunderstorms roughly 170km (105mi) long. This MCS crossed the border into western Germany at around 8 pm and began to develop a large bowing segment.[24] By 9 pm, the MCS had developed into a violent bow echo and moved across the Rhine-Ruhrmetropolitan region with hurricane-force winds affecting roughly 10 million people. Large scale chaos and damage was the result, and the storm was later determined to be the most damaging weather event in this area in decades.[5] All 6 fatalities from this outbreak were a result of the intense bow echo, and the cost of damage was estimated at 650 million euros, just from this single event.[25] Peak winds of 144km/h (89mph) were measured in Düsseldorf at the airport, however based on the extent of damage, it is believed that windspeeds may have reached around 150km/h (93mph).[26] The city of Neuss saw a top windspeed of 133km/h (83mph) and in the Ruhr city of Castrop-Rauxel a wind of 124km/h (77mph) was reported during the passage of the storm.[27] In the area around 40 liters of rainfall per square meter fell.[28]
Meanwhile, new severe thunderstorms, some of them supercells, had developed again in the western half of France, producing intense winds and very large hail. The town of Ardon was hit by a supercell at around 9:30 pm, which produced hail up to 11cm in diameter.[20] A 130km/h (81mph) windgust was recorded in Cognac, Charente. This was the fourth highest gust since 1981 and the highest since the passage of Cyclone Lothar and Martin in December 1999, when a 158km/h (98mph) gust was measured.[29] At Melle, Deux-Sèvres in western France, winds up to 120km/h (75mph) were recorded, which is the second highest gust recorded since the opening of the station, after that observed during the passage of Cyclone Lothar and Martin in December 1999.[29]
In Germany, the bow echo began to weaken drastically after 11 pm as it moved east into central Germany. However it would continue to produce strong and partly severe winds until crossing the border into Poland the following morning, where it finally dissipated.
June 10
Damage to a forest in Recklinghausen, Germany, after the intense bow echo
Upon reaching the Paris area around midnight, the supercells from the previous evening merged into an MCS once again. While being significantly weaker, this system would produce some more damage as it moved over the previous bow echo's path, before dissipating in northern Germany at around 9 am.
A large branch fell onto a car in Neuss, Germany
The trough responsible for the outbreak was forced to move northward on June 10 due to a new low pressure system pushing in from the Atlantic. By 5 pm, the centre was located over the northern British Isles, while its frontal zone had advanced eastward. As a result, the jet with the strongest windshear was no longer overlapping with the highest instability, and the environment was overall less favourable for severe weather compared to the previous two days. The risk area had also shifted eastward and now stretched from eastern France into southern and central Germany. Still, severe thunderstorms and supercells developed. 5cm hail was recorded near Kassel, and a 90km/h (56mph) wind gust was measured in Chargey-lès-Gray.[20]
June 11
On June 11, Iberia and the western half of France came under the influence of a new high pressure system. Meanwhile, the frontal zone of the trough had almost reached the Alps, effectively cutting off the flow of hot and moist air into western and central Europe. Still, a large pocket of instability remained over eastern Germany, western Poland and parts of Czechia, where thunderstorm activity would focus on the last day of the outbreak.[30] Thunderstorms from the previous day in France had moved into central Germany after weakening overnight, but were able to gradually restrengthen again after sunrise. They grew upscale into an MCS around noon and reached northeastern Germany. A strong vortex embedded in this MCS spawned at least three tornadoes in southern Mecklenburg-Vorpommern, with the first one touching down at 1:37 pm. This tornado received an F1 rating after causing significant vegetation damage in a forest along a 2.2km long path. At 1:40 pm, a second tornado touched down just to the north of the first tornado, and devastated a forest along a 3.7km long track. This tornado was given an F2 rating. It is believed that both tornadoes coexisted for some time while being less than 2km away from each other. The third tornado occurred at 1:58 pm and hit the village of Blumenhagen, damaging roofs and snapping trees. A pavilion was reportedly lifted 150 m into the air and thrown. The maximum damage along the 2.1km long path was determined to be F1.[31] The storm cluster also produced large hail and severe winds, before moving off into Poland and dissipating later that evening. A windspeed of 113km/h (70mph) was recorded in Kyritz, Brandenburg, and 6cm large hail was observed in Kodersdorf, Saxony.[20]
Between Saturday 7 and Tuesday 10 June morning, there fell in total 55mm of rain Saint-Sauveur-Marville Marville (Eure-et-Loir), which corresponds to 5–6 weeks worth of rainfall during an average June in Paris.
The total number of lightning discharges on 9 June was more than 64,000 in the Netherlands, such a number is on average only seen once per summer season.[21] The bow echo produced an estimated 113,708 lightning strikes across Germany between 2pm 9 June and 8am 10 June.[32]
A thunderstorm, also known as an electrical storm or a lightning storm, is a storm characterized by the presence of lightning and its acoustic effect on the Earth's atmosphere, known as thunder. Relatively weak thunderstorms are sometimes called thundershowers. Thunderstorms occur in a type of cloud known as a cumulonimbus. They are usually accompanied by strong winds and often produce heavy rain and sometimes snow, sleet, or hail, but some thunderstorms produce little precipitation or no precipitation at all. Thunderstorms may line up in a series or become a rainband, known as a squall line. Strong or severe thunderstorms include some of the most dangerous weather phenomena, including large hail, strong winds, and tornadoes. Some of the most persistent severe thunderstorms, known as supercells, rotate as do cyclones. While most thunderstorms move with the mean wind flow through the layer of the troposphere that they occupy, vertical wind shear sometimes causes a deviation in their course at a right angle to the wind shear direction.
A supercell is a thunderstorm characterized by the presence of a mesocyclone, a deep, persistently rotating updraft. Due to this, these storms are sometimes referred to as rotating thunderstorms. Of the four classifications of thunderstorms, supercells are the overall least common and have the potential to be the most severe. Supercells are often isolated from other thunderstorms, and can dominate the local weather up to 32 kilometres (20 mi) away. They tend to last 2–4 hours.
A severe thunderstorm watch is a statement issued by weather forecasting agencies to advise the public that atmospheric conditions in a given region may lead to the development of severe thunderstorms within the region over several hours. The criteria for issuing a watch varies from country to country and may also include torrential rainfall and tornadoes. A watch may also be issued several hours ahead of the arrival of a mature and organized complex of storms, such as a mesoscale convective system.
A severe thunderstorm warning is a type of public warning for severe weather that is issued by weather forecasting agencies worldwide when one or more severe thunderstorms have been detected by Doppler weather radar, observed by weather spotters, or reported by an emergency management agency, law enforcement, or the general public. Unlike a watch, a warning is issued to areas in the direct path of active severe thunderstorms, that are expecting a direct impact typically within an hour. Severe thunderstorms can cause property damage and injury due to large hail, high winds, and flooding due to torrential rainfall. The exact criteria to issue a warning varies from country to country.
A squall line, or more accurately a quasi-linear convective system (QLCS), is a line of thunderstorms, often forming along or ahead of a cold front. In the early 20th century, the term was used as a synonym for cold front. Linear thunderstorm structures often contain heavy precipitation, hail, frequent lightning, strong straight-line winds, and occasionally tornadoes or waterspouts. Particularly strong straight-line winds can occur where the linear structure forms into the shape of a bow echo. Tornadoes can occur along waves within a line echo wave pattern (LEWP), where mesoscale low-pressure areas are present. Some bow echoes can grow to become derechos as they move swiftly across a large area. On the back edge of the rainband associated with mature squall lines, a wake low can be present, on very rare occasions associated with a heat burst.
The Late-May 1998 tornado outbreak and derecho was a historic tornado outbreak and derecho that began on the afternoon of May 30 and extended throughout May 31, 1998, across a large portion of the northern half of the United States and southern Ontario from southeastern Montana east and southeastward to the Atlantic Ocean. The initial tornado outbreak, including the devastating Spencer tornado, hit southeast South Dakota on the evening of May 30. The Spencer tornado was the most destructive and the second-deadliest tornado in South Dakota history. A total of 13 people were killed; 7 by tornadoes and 6 by the derecho. Over two million people lost electrical power, some for up to 10 days.
A bow echo is the characteristic radar return from a mesoscale convective system that is shaped like an archer's bow. These systems can produce severe straight-line winds and occasionally tornadoes, causing major damage. They can also become derechos or form Line echo wave pattern (LEWP).
Severe storms in Australia refers to the storms, including cyclones, which have caused severe damage in Australia. For comparison, a comprehensive list of all damaging storms can be found on the Australian Bureau of Meteorology website.
This article describes severe weather terminology used by the Meteorological Service of Canada, a branch within Environment and Climate Change Canada. The article primarily describes various weather warnings, and their criteria. Related weather scales and general weather terms are also addressed in this article. Some terms are specific to certain regions.
The Corn Belt derecho was a progressive derecho which affected a large area of the central United States on June 29, 1998. In the morning, thunderstorms, including a supercell, developed over South Dakota and tracked into central Iowa. As the thunderstorms reached central Iowa, a strong rear-inflow jet developed which caused the thunderstorm to take on a different characteristic, becoming a derecho. It traveled more than 600 miles in about ten hours, causing more than $125 million worth of widespread damage destruction, especially to crops, and was responsible for power outages to nearly a half a million people.
On February 10–11, 2009, a broad-scale damaging wind event and small tornado outbreak affected the Central and Eastern United States. During the two-day period, 14 tornadoes touched down in seven states. Oklahoma was struck by six tornadoes, the most of any state. The six tornadoes in Oklahoma also tied the record for the most tornadoes ever recorded in the state during the month of February, which would later be broken in 2023. The first day of the outbreak produced the most tornadoes; the second brought mainly high wind damage and rain or snow in most of the Northeast.
From May 3 to May 11, 2003, a prolonged and destructive series of tornado outbreaks affected much of the Great Plains and Eastern United States. Most of the severe activity was concentrated between May 4 and May 10, which saw more tornadoes than any other week-long span in recorded history; 335 tornadoes occurred during this period, concentrated in the Ozarks and central Mississippi River Valley. Additional tornadoes were produced by the same storm systems from May 3 to May 11, producing 363 tornadoes overall, of which 62 were significant. Six of the tornadoes were rated F4, and of these four occurred on May 4, the most prolific day of the tornado outbreak sequence; these were the outbreak's strongest tornadoes. Damage caused by the severe weather and associated flooding amounted to US$4.1 billion, making it the costliest U.S. tornado outbreak of the 2000s. A total of 50 deaths and 713 injuries were caused by the severe weather, with a majority caused by tornadoes; the deadliest tornado was an F4 that struck Madison and Henderson counties in Tennessee, killing 11. In 2023, tornado expert Thomas P. Grazulis created the Outbreak Intensity Score (OIS) as a way to rank various tornado outbreaks. The tornado outbreak sequence of May 2003 received an OIS of 232, making it the fourth worst tornado outbreak in recorded history.
The 1995 Mayfest storm was a damaging hailstorm that struck parts of the Dallas–Fort Worth metroplex on May 5, 1995. It was the first singular thunderstorm with a damage toll exceeding $1 billion and at the time the costliest nontornadic thunderstorm in U.S. history. Hail up to 4.5 in (11.5 cm) in diameter fell across Parker and Tarrant counties, producing hail drifts as deep as 3 ft (0.91 m) and damaging numerous buildings. The storm also struck the Fort Worth Mayfest – a local outdoor festival – pelting the roughly 10,000 people in attendance with softball-sized hail and resulting in over 60 hospitalizations. Though there were no hail-related fatalities, the combination of the slow-moving supercell that produced the hail and a larger complex of storms led to deadly flash flooding that killed 17 people in the Dallas area. Overall, 20 people were killed by the storms.
The Spanish Plume is a weather pattern in which a plume of warm air moves from the Iberian plateau or the Sahara to northwestern Europe, causing thunderstorms. This meteorological pattern can lead to extreme high temperatures and intense rainfall during the summer months, with potential for flash flooding, damaging hail, and tornado formation. Some of these intense thunderstorms are formed from thermal lows, which are also known as heat lows. Thermal lows can be semipermanent features around some parts of Europe, particularly in the summer season. These thermal lows can be developed or created around Spain, Portugal, France etc., during the summer season because of the intense heat. Thermal low pressure can be located around the world, particularly in the summer or in tropical regions.
A significant and destructive tornado outbreak that affected parts of the Midwestern United States and lower Great Plains in mid-May 2013. This event occurred just days after a deadly outbreak struck Texas and surrounding southern states on May 15. On May 16, a slow moving trough crossed the Rockies and traversed the western Great Plains. Initially, activity was limited to scattered severe storms; however, by May 18, the threat for organized severe thunderstorms and tornadoes greatly increased. A few tornadoes touched down that day in Kansas and Nebraska, including an EF4 tornado near Rozel, Kansas. Maintaining its slow eastward movement, the system produced another round of severe weather nearby. Activity significantly increased on May 19, with tornadoes confirmed in Oklahoma, Kansas, Iowa, Missouri, and Illinois. In Oklahoma, two strong tornadoes, one rated EF4, caused significant damage in rural areas of the eastern Oklahoma City metropolitan area; two people lost their lives near Shawnee. The most dramatic events unfolded on May 20 as a large EF5 tornado devastated parts of Moore, Oklahoma, killing 24 people. Thousands of structures were destroyed, with many being completely flattened. Several other tornadoes occurred during the day in areas further eastward, though the majority were weak and caused little damage.
The following is a glossary of tornado terms. It includes scientific as well as selected informal terminology.
A deadly and destructive outbreak sequence of 23 tornadoes struck parts of the Great Plains and the Great Lakes in late-June 1957. At least seven significant tornadoes (F2+) touched down during the outbreak sequence. The most devastating storm was a large, violent, and catastrophic 500-yard-wide F5 tornado family that struck Fargo, North Dakota on Thursday, June 20, 1957, killing 10 people and becoming the deadliest tornado ever recorded in North Dakota. The outbreak caused 11 fatalities, 105 injuries, and $25.883 million in damage.
The 2022–23 European windstorm season was the deadliest and costliest European windstorm season on record, mainly because of the impact in Northern Libya of Storm Daniel, which became the deadliest and costliest medicane ever recorded as well as the deadliest tropical or subtropical system worldwide since 2008.
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