Understanding the underexplored role of deeper ocean layers in hurricane dynamics is pivotal amidst escalating storm intensities and growing threats to coastal communities. While early forecasting approaches focused almost exclusively on near-surface variables (e.g. sea surface temperature) or upper-ocean layers (0â100 m), some follow-up efforts integrated subsurface information using ocean heat content analyses relative to the 26 °C isotherm, yielding modest enhancement for the most intense storms. By contrast, our convolutional neural networkârandom forest (RF) framework explicitly exploits the threeâdimensional structure of ocean anomalies from the surface down to 500 mâindirectly capturing heat redistribution, salinityâdriven stratification, and mixedâlayer dynamics across depths. We demonstrate that the layered information within 40â500 m accounts for 44.91 ± 0.24% of total variable importance in the RF model and supports 72-h leadâtime severeâhurricane forecasts with a precision of 73.04 ± 7.95%. This substantially extends ocean-heat-contentâonly approaches by: 1) avoiding a hard threshold, 2) providing the first quantification of layer-specific subsurface contributions to severity forecasting through a multi-depth anomaly analysis across multiple variables using an RF-based framework, and 3) leveraging fineâscale spatial patterns via convolutional-neural-networkâderived features. Subsurface variables down to 500 m are not merely ancillaryâthey are indispensable for capturing the ocean precursors of the strongest hurricanes, particularly when the 26 °C isotherm (typically shallower than 100 m) fails to represent the full heat reservoir. This deeper thermal structure may represent a key energy source that can supportâand potentially accelerateâsevere hurricane intensification. These findings highlight the untapped predictive value of deep-layer ocean information and its potential to enhance early-warning systems for high-impact storm events.