AbstractHarvey entered the Gulf of Mexico as a tropical depression on 23 August 2017; two days later it had strengthened to a category 1 hurricane. Over the following 30 hr Harvey rapidly intensified, reaching the Texas Bight as a category 3 storm. This intensification continued while Harvey crossed the shelf, making landfall as a category 4 storm 60 km east of Corpus Christi, TX on 26 August. A hydrographic survey two weeks prior to landfall shows that the tropical cyclone heat potential across the Texas Bight was approximately 35 kJ/cm2, which is 55 kJ/cm2 less than the amount of upper ocean heat normally associated with intensification. Combined with buoy, float, and satellite data, we use hydrographic surveys to study the conditions of the Texas Bight that contributed to Harvey's rapid intensification. We find that, at the time of landfall, the Texas Bight was well mixed with very warm water extending from the surface to bottom. As a consequence, mixing induced by Harvey had a small impact on surface temperatures which remained high and supported continued intensification. The results show that tropical cyclone heat potential is not an effective metric for hurricane intensity prediction in shallow water, and illustrate the need for continuous subsurface monitoring in order to improve hurricane forecasts.