Anticipatory Action Drought Trigger Development & Forecast Evaluation

Central American Dry Corridor | 2026 Season Update

Overview

This book documents the forecast evaluation and trigger design process for drought anticipatory action in the Central American Dry Corridor (Guatemala, Honduras, El Salvador) for the 2026 season.

Part I: Forecast Skill Evaluations

These analyses were conducted based on the framework as it stood at the time of writing, with a primary focus on Guatemala (Chiquimula) and the central question of which seasonal forecast system — ECMWF SEAS5 or INSIVUMEH — to use for drought prediction. The evaluation spans binary and continuous metrics, multiple observation sources, temporal stability, and internal consistency diagnostics.

Part II: 2026 Trigger Design & Tuning

Building on the forecast evaluation findings, this section presents a more detailed analysis to refine the operational trigger configurations for 2026. A common methodology was developed — systematic exploration of areas of interest, leadtime selection, and threshold optimization, grounded in both historical rainfall skill (ERA5) and humanitarian impact records (EM-DAT, CERF) — and applied consistently across all three countries. This process led to updated AOI definitions and forecast skill benchmarks that differ from the initial framework assumptions. Country-specific trigger configurations are recommended for Honduras, El Salvador, and Guatemala. For Guatemala, a parallel analysis was conducted for the StartNetwork programme, covering distinct AOIs and exploring multiple trigger variants to accommodate different operational scenarios and partner priorities.