# EVA 2025: EXALT Project Participation

In July 2025, EXALT researchers contributed to EVA 2025 with three invited talks and four PhD posters on probabilistic forecasting, multivariate extremes, and rare-event simulation.

Conference Talks

Tail Calibration of Probabilistic Forecasts

Prof. Johan Segers

Focused on a general notion of tail calibration for probabilistic forecasts, with diagnostic tools and a case study on European precipitation.

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Probabilistic forecasts describe uncertainty in future outcomes and support decision making. Standard verification tools are often weak for tail behavior, although extreme outcomes usually matter most for risk. This talk introduced a general framework for tail calibration, linked it to standard calibration notions, and discussed connections with peaks-over-threshold methods in extreme value theory.

X-vine Models for Multivariate Extremes

Prof. Anna Kiriliouk

Presented X-vines, a flexible construction for exponent measure densities in multivariate extremes using regular vine sequences.

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The talk showed how regular vine structures can decompose and construct high-dimensional extreme-value models through bivariate components. It covered simulation for X-vine multivariate Pareto models, parameter estimation, and model selection from threshold excesses, with applications and extensions toward quantile regression in extreme covariate regions.

Simulation of Extreme Events with Rare Event Algorithms

Prof. Francesco Ragone

Discussed how rare-event algorithms improve sampling efficiency for extreme events in complex numerical models.

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Robust extreme-event analysis in numerical models often needs very long simulations or very large ensembles. Rare-event algorithms reduce this burden using cloning and suppression strategies that oversample trajectories associated with target events. The presentation highlighted applications to temperature and sea-ice extremes, with perspectives for tipping points and early-warning validation.

PhD Poster Session