Abstract
<jats:p>This preprint provides a hydrological and hydrogeological interpretation of ECMWF SEAS5 monthly precipitation forecasts for Iraq from October 2026 through January 2027. The analysis uses the ECMWF System 51 ensemble mean initialized on 1 August 2026. The downloaded time-mean total precipitation rate was converted from metres per second to monthly precipitation depth in millimetres using the actual number of days in each valid month. The original 1° × 1° analytical grid was retained without spatial smoothing and clipped to the supplied national boundary of Iraq. Derived products include four-month precipitation accumulation, peak monthly rainfall, rainfall concentration, temporal variability, maximum month-to-month increase, a transparent precipitation-only screening index, relative screening classes, and three-dimensional visualizations. The forecast exhibits a strong north–northeast precipitation gradient. Representative four-month totals are 574.24 mm near Erbil, 483.87 mm near Sulaymaniyah, 348.92 mm near Kirkuk, and 294.13 mm near Duhok, compared with 140.34 mm near Baghdad and 113.31 mm near Basra. The strongest seasonal hydrological signal therefore occurs across northern and northeastern Iraq. Hydrogeologically, enhanced winter precipitation may increase diffuse and focused recharge in permeable alluvial, fractured, and karstic aquifers, but monthly rainfall alone cannot quantify recharge. Likewise, the rainfall-screening maps are preliminary regional prioritization products rather than physical flood-hazard or inundation maps because they do not include topography, drainage, soil, land cover, antecedent moisture, rainfall intensity, river capacity, or observed flood inventories. The products should therefore be used as a seasonal hydroclimatic outlook and as a first-stage prioritization layer for subsequent high-resolution hydrological, hydraulic, and hydrogeological modelling.</jats:p>