DESPITE GLOBAL WARMING, COLD SPELLS SUCH AS WITNESSED IN THE 1980’s IN WESTERN EUROPE ARE STILL POSSIBLE
Extreme cold spells are still possible today in Western Europe, even with current warming trends.
The atmospheric circulation patterns that drive extreme low temperatures, e.g. as in January 1985, remain possible in current winters.
Under such conditions we anticipate that with current regional warming trends, temperatures would only be about 1.4°C warmer than in 1985, with potential impacts on the electricity grid, and health.
As an example, a circulation-induced 1985-like cold spell in today’s climate would likely stand at around -9°C over France for minimum temperatures, which would still be amongst the 5-10 coldest cold spells observed in the past five decades.
Medicanes are Mediterranean cyclones whose characteristics resemble those of tropical cyclones. They are often associated with hurricane-force winds and heavy precipitation. With a frequency of 1-2 per year, it is a challenge to determine whether their frequency should increase or decrease in a warmer world. Their intensity is however projected to increase due to the warming projections for the Mediterranean sea, the main source of energy for medicanes.
Located in Sorbonne University, Paris France, the XAIDA’s First General Assembly will take place from 12 to 14 October 2022, in an hybride format.
In the second part of November 2002, the synoptic situation over the Mediterranean was characterized by a sequence of perturbations entering the area from the North Atlantic. In particular, the persistence of an upper-level North-Atlantic trough between the 23th and 27th of the month, set the conditions for very heavy precipitation over North Italy with high ground impact over some areas and floods (i.e. Milan, Pordenone). The impact at ground was possibly amplified by the ground wet saturation for precipitations that occurred in the previous period. The evolution of the perturbation entering the Mediterranean basin on Nov. the 24th was very slow due to a steady North Africa high pressure blocking the central-east basin side.
This event affected the South of France during September 8th-9th, 2002, and it was characterized by the formation and evolution of a major mesoscale convective system (MCS). The event caused one of the most important flood recorded in the Cevennes-Vivarais region, with 24 people killed and economic loss estimated at 1.2 billion euros (Huet et al., 2003). The MCS was driven by a deep low pressure extending from Scotland to the western Mediterranean with an associated surface cold front. The prefrontal flow induced relatively warm and humid air into the South of France, feeding the convective system. The combination of cold temperature at mid-levels (850 hPa) and humidity at low-to-mid levels were the perfect ingredients for convection to form during the event. A further injection of wet air due to the circulation around the Southern Alps contributed to intensify the event. The maximum values of precipitation exceeded 600 mm in the region of Anduze and Alès (Delrieu et al., 2005).
Hurricane Irma was a Cape Verde-type hurricane, the most intense hurricane observed in the Atlantic Ocean since Hurricane Dean in 2007. It was also the most powerful Atlantic hurricane to hit the U.S. since Katrina in 2005 and the first major hurricane (Category 3 or higher on the Saffir-Simpson scale) to make landfall in Florida since Hurricane Wilma in 2005. Irma was the ninth named tropical storm, the fourth hurricane, and the second major hurricane of the 2017 season.
Winter cold spells in Europe can be accompanied by anomalously weak winds. Usually, the reason is a so-called “blocked” atmospheric circulation, leading to advection of cold air downstream and a weaker than normal warming westerly flow. This creates a situation where energy demand is high, but power production from renewables is low, leading to higher risk of energy shortfall (Figure 1). With the transition towards more renewable energies in Europe, the energy sector will also become more weather-dependent, making it necessary to understand potential changes in the frequency and intensity of combined cold/wind drought winters.
The spring of 2021 showed anomalously low temperatures across large areas of Europe (see Figure 1). These extreme temperatures likely contributed to impacts in different sectors (energy, health, agriculture). In particular, several frost nights in early April in France caused damage to the regional wine industry as the cold temperatures occurred after anomalously warm temperatures in March, thus, right in the sensitive phase after bud-burst.
During the last days of July 2021 a region in the Northwestern US and southwestern Canada experienced temperatures that have never been previously observed in this region, with records broken in many places by several degrees (Philip et al. 2021). A new all-time Canadian temperature record of 49.6°C was set in the town of Lytton, British Columbia. The same town was strongly affected and partly destroyed by one of the severe wildfires that occurred during and after the heatwave. The Pacific Northwest heatwave further contributed to a sharp increase in heat-related excess mortality. The Pacific Northwest heat wave is one of a series of record-shattering heat extremes that, based on the previous observational record, may have been deemed impossible.
Medicane Apollo (named by a consortium of European meteorological services) formed on October 28th in the Jonian sea, offshore Sicily, from a low pressure disturbance which was very active in the days previous the formation of the Medicane. This low pressure system was isolated near the Balearic islands around 22nd of October and then moved on the Central Mediterranean sea producing self-regenerating thunderstorms in the area of Catania on the 24th of October.