S2S-JEPA: Predicting the Predictable at Subseasonal-to-Seasonal Timescales

Chenyu Dong; Gianmarco Mengaldo

Home/Archive/arXiv

arXiv · 2610.03106

S2S-JEPA: Predicting the Predictable at Subseasonal-to-Seasonal Timescales

Chenyu Dong·Gianmarco Mengaldo

View original source ↗Read source document ↗Export metadata ↓

Abstract

The subseasonal-to-seasonal (S2S) timescale, roughly from two weeks to two months ahead, is a critical forecast window for sectors such as agriculture, energy, and water management. Yet, it is widely known as the `predictability desert'. Recent AI weather models excel up to two weeks ahead but deteriorate beyond, largely because they are trained to predict fine-scale details that are neither predictable nor essential at S2S timescales. We argue that a more physically grounded objective is to forecast only the slowly varying components that remain predictable. Computer vision reached the same conclusion with the Joint-Embedding Predictive Architecture (JEPA), which predicts in latent space, discarding unpredictable details. In this work, we introduce S2S-JEPA, which brings the JEPA paradigm to S2S forecasting. It is tailored to this task through design elements from state-of-the-art AI weather models. S2S-JEPA achieves comparable skill to the gold-standard ECMWF physics-based ensemble and surpasses it on multiple metrics at weeks 5 to 6.

Explore related subjects

physics.ao-ph cs.AI cs.LG

Keep this discovery

Explore connections, maps & timelines

BibTeX RIS

Chenyu Dong, Gianmarco Mengaldo. 2026-10-02. S2S-JEPA: Predicting the Predictable at Subseasonal-to-Seasonal Timescales. https://arxiv.org/abs/2610.03106

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related papers

arXiv2026

Baseline Climatology of Tornadoes and Waterspouts in the Philippine Archipelago

Tornadoes are documented on every inhabited continent, yet the environmental conditions used to anticipate them were developed and validated overwhelmingly on mid-latitude records, leaving tropical regimes largely unexamined. Here, we collected 1,186 combined tornado and waterspout reports in the Philippines spanning the early 1900s to 2025 and paired each with an ERA5 proximity sounding to construct the first baseline climatology and environmental characterization of these events in the archipelago. Activity concentrates in three corridors, mostly flanked by mountain ranges, one in each major island group, and is sharply phased within a May-October window that closely tracks the annual cycle of thunderstorm frequency, peaking in August and lagging into October for waterspouts alongside the tropical cyclone season. These events cluster in the mid-to-late afternoon, consistent with a daytime heating regime rather than nocturnal convection. The environments are thermodynamically permissive but kinematically shallow, with convective available potential energy (CAPE) exceeding typical Great Plains values, while the 0-6 km bulk wind difference (BWD; DLS) remains weak at $\sim$10-14 kt, departing from the mid-latitude covariance in which instability and shear increase together. Although streamwise vorticity is modest in magnitude, nearly all discriminating variance resides in the lowest kilometer, where 68-79% of near-surface horizontal vorticity is streamwise, reaching $>$0.005 s$^{-1}$ and 96% streamwiseness in the most organized profiles, and the hodographs retain low-level curvature. Consequently, composite indices remain low even as tornadoes and waterspouts recur. Mid-latitude-calibrated parameters can therefore misdiagnose tropical-maritime regimes, and recalibration toward shallow-layer, orientation-aware kinematic discriminators may recover the diagnostic signal.

physics.ao-ph↗

arXiv2026

Stochastic thermodynamics and predictability of Ornstein-Uhlenbeck processes: an application to the Madden-Julian Oscillation

Climate oscillations are intrinsically out-of-equilibrium phenomena, yet the connection between their predictability and nonequilibrium thermodynamic properties remains unexplored. We develop a coarse-grained stochastic thermodynamic framework for Ornstein-Uhlenbeck (OU) processes and apply this framework to climate data via linear inverse models (LIMs), linking predictability, entropy production, dynamical activity, and path action. Climate oscillations are often studied in a 2d phase space of climate indices, which are even under time-reversal, motivating our focus on 2d OU dynamics with even variables. We find that coordinate-invariant properties of 2d OU processes can be reduced to a minimal three-parameter description: two diffusivities and a phase-space rotation. We show that these quantities fundamentally characterize distinct aspects of the dynamics. We find that higher irreversibility and dynamical activity do not necessarily imply reduced predictability. Rather, it is the path action which is most closely connected to a commonly used measure of predictability, the anomaly correlation coefficient (ACC). As an illustrative example, we apply this framework to the Madden-Julian Oscillation (MJO) over the twentieth century. We find that the MJO has become simultaneously more predictable, as seen previously, while at the same time becoming more irreversible and more active. Predictability is driven predominantly by the reduced mean diffusion. Entropy production reflects the combined evolution of all three parameters. These results suggest that stochastic thermodynamics provides a powerful lens for studying nonequilibrium climate phenomena.

physics.ao-ph↗

arXiv2026

On the instability of some upward propagating, exact, nonlinear mountain waves

Using the short-wavelength instability method, we investigate the linear instability of an exact solution describing upward-propagating mountain waves, derived in A.~Constantin, \emph{J. Phys. A: Math. Theor.} (2023), for a dry and adiabatic compressible flow. Within this approach, the stability problem reduces to the analysis of a system of ordinary differential equations with periodic coefficients along the fluid trajectories, which we study by means of Floquet theory. We show that the Floquet multipliers are of the form $\{1,μ,μ^{-1}\}$, the multiplier $1$ being associated with the conservation of potential vorticity, so that stability is decided by a single discriminant, which coincides with that of a Hill equation. For neutral stratification the flow is unstable whenever the wave steepness exceeds the critical value $\frac{1}{3}$, while a weakly stable stratification lowers this threshold to $\frac{1}{3}-\frac{4}{9}ν^2+O(ν^4)$, $ν$ being the ratio between the Brunt--Väisälä frequency and the orbital frequency of the air parcels. The instability is a subharmonic parametric resonance. Since the solution is given in Lagrangian coordinates, these results identify an unstable region in the upper part of the laminar layer, beneath the tropopause, where the wave is steepest.

physics.ao-ph↗