Storm Gloria: Sea State Evolution Based on in situ Measurements and Modeled Data and Its Impact on Extreme Values

Abstract

Storm Gloria, generated on January 17th, 2020 in the Eastern North Atlantic, crossed the Iberian Peninsula and impacted the Western Mediterranean during the following days. The event produced relevant damages on the coast and the infrastructures at the Catalan-Balearic Sea, due to extraordinary wind and wave fields, concomitant with anomalously intense rain and ocean currents. Puertos del Estado (the Spanish holding of harbors) has developed and operates a complex monitoring and forecasting system (PORTUS System), in collaboration with the Spanish Met Office (AEMET). The present work shows how Gloria was correctly forecasted by this system, alerts were properly issued (with special focus to the ports), and the buoys were able to monitor the sea state conditions during the event, measuring several new records of significant wave height and exceptional high mean wave periods. The paper describes, in detail, the dynamic evolution of the atmospheric conditions, and the sea state during the storm. It is by means of the study of both in situ and modeled PORTUS data, in combination with the AEMET weather forecast system results. The analysis also serves to place this storm in a historical context, showing the exceptional nature of the event, and to identify the specific reasons why its impact was particularly severe. The work also demonstrates the relevance of the PORTUS System to warn, in advance, the main Spanish Ports. It prevents accidents that could result in fatal casualties. To do so, the wave forecast warning performance is analyzed, making special focus on the skill score for the different horizons. Furthermore, it is demonstrated how a storm of this nature results in the need of changes on the extreme wave analysis for the area. It impacts all sorts of design activities at the coastline. The paper studies both how this storm fits into existing extreme analysis and how these should be modified in the light of this particular single event. This work is the first of a series of papers to be published on this issue. They analyze, in detail, other aspects of the event, including evolution of sea level and description of coastal damages.

Understanding Sea Level Processes During Western Mediterranean Storm Gloria

“…While coastal damages were reported all along the WM coasts, sea levels measured by tide gauges (TGs hereafter) were only particularly extreme at the region of Valencia (Gandía, Sagunto, and Valencia TGs), followed by the South of Catalonia (Tarragona TG). This contrasts with the record-breaking measured wave heights (see De Alfonso et al, 2021), that seems to make waves the main driver of coastal problems during this event. Still, a detailed analysis of different timescales of sea level variability as provided by TGs, and their spatial variation, has helped to understand its role during the storm Gloria.…”

“…Note that these local waves will depend strongly on the tide gauge location inside the harbor. Tarragona, Sagunto and Valencia are the ones most exposed to the open ocean wave conditions, particularly extreme during this storm (De Alfonso et al, 2021).…”

“…Orange or yellow level notices were issued for the rest of the Mediterranean coastlines. Several buoys beat their record of significant wave height, that reached 8.44 m at Valencia buoy (see AEMET Report, 2020;De Alfonso et al, 2021, for a detailed meteorological and wave description of the storm). A mostly wind-driven storm surge was observed along the coastline of Spanish mainland, combined with a significant wave setup contribution at specific spots (Ebro Delta, between Valencia and Denia), according to Amores et al (2020).…”

“…The paper is one of a series of studies that assess the performance of the PORTUS system and Copernicus Marine Service (CMEMS) products for different variables and aspects of the storm Gloria: record wave heights from buoys and wave models (De Alfonso et al, 2021); validation of currents, temperature and salinity of the CMEMS regional model for the Iberia Atlantic coast (IBI) (Sotillo et al, 2021); and performance of HF-radar measurements (Lorente et al, 2021).…”

Evaluation of the Operational CMEMS and Coastal Downstream Ocean Forecasting Services During the Storm Gloria (January 2020)

“…The authors emphasize that this work is only addressing the analysis of oceanographic dynamics, because it is part of a series of studies analyzing several specific aspects related to the Gloria event, including monitoring and modeling of waves, sea level evolution, and the description of coastal damages and impacts. Thus, for a more detailed description of Storm Gloria (put in context with other historical exceptional events that occurred in the region: such as the San Esteban 2008 or the November 2001 storms - Sánchez-Arcilla et al, 2008;Bolaños et al, 2009;Gràcia et al, 2013;Sánchez-Arcilla et al, 2014) or for analyses focused on the storm's associated surge and wave states, the reader can consult Pérez-Gómez et al (2021, unpublished data) andDe Alfonso et al (2021). With respect to the remarkably diverse coastal impacts, and especially on the severely affected Ebro Delta region (with the delta almost disappeared due to the low-lying flooding) Lorente et al (2021) provide a specific analysis on such topic.…”