The 19 January 2013 windstorm over the North Atlantic: large-scale dynamics and impacts on Iberia

Abstract On 19 January 2013 Portugal was once again on an extreme meteorological risk warning state due to the landfall of a rapidly deepening low pressure system exactly on the period of its maximum explosive development. This storm, named Gong, had a central minimum pressure of 968 hPa, observed wind gusts of 140 km h−1 on some locations of the Portuguese coast and was responsible for the downfall of thousands of trees on some of the Portuguese national forests, the destruction of several hundred farms among other huge socioeconomic losses and fatalities. The large-scale synoptic conditions and dynamical characteristics of windstorm Gong, as well as the associated meteorological and socioeconomic adverse impacts are reviewed in this paper. For this purpose an objective lagrangean method, which identifies and follows individual lows, is applied for the assessment of the cyclone track and lifetime characteristics, which is complemented by the analysis of several thermohydrodynamical reanalysis fields during the lifetime of the cyclone. Results show that Gong underwent an explosive development with ‘bomb’ characteristics between the Azores and the Iberian Peninsula, with a deepening rate unusually high for these latitudes. The rapid deepening of Gong was supported by the southerly displacement of the polar jet stream; by a pronounced cyclonic potential vorticity streamer which approached Iberia from northwest; and by the presence of an atmospheric river over the western and central subtropical North Atlantic converging into Gong׳s genesis region and then crossing the Atlantic basin, moving along with the storm towards Iberia. Understanding the dynamics of these high impact extreme events may be of relevance in view of improving extreme forecasts as well as of public awareness, policy making and risk assessment and management of severe weather in Portugal.

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