Award: OCE-1760381

Texas A&M University was awarded a RAPID grant to invesigate the impact of rainfall from Hurricane Harvey. As a rapid response, we proposed two cruises on the RV Pelican to carry out an investigation of the effects and potential impacts of the freshwater run-off from Hurricane Harvey. The first cruise was completed 22nd Sept. to 1st Oct. and the second was completed 15th-20th Nov. In addition to the two cruises, a suite of oceanographic physio-chemical measurements were made. This included the use of a Liquid Robotics SV3 Wave Glider to follow the freshwater plume, a Teledyne-Webb buoyancy glider to determine the depth and characteristics of the freshwater intrusion and its evolution between cruises, and data from two cruises in June and August 2017 prior to Hurricane Harvey. The data from the two cruises was compared to data collected in June 2017 and August 2017 prior to Hurricane Harvey?s landfall in late August 2017. Hurricane Harvey 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. Hurricanes rely on heat extracted from the upper ocean as their energy source. When the ocean is warm conditions are more favorable and hurricanes are often stronger. Hurricanes also mix the ocean which brings cold water from greater depth and can lead to intensity reduction. Tropical cyclone heat potential is a measure of heat in the upper ocean which is available as an energy source for hurricanes. In shallow water tropical cyclone heat potential is typically low because there is not as much water to store heat; therefore, hurricanes are not expected to intensify over shallow water. we show that hurricane Harvey did intensify over the shallow water off the Texas coast despite having low heat potential. Using ocean measurements, we found that the reason was because the ocean was very warm from the surface to the seabed. Therefore, when Harvey mixed the ocean very little cold water was brought up from below and the surface remained warm which allowed Harvey to continue to strengthen. Results suggest that tropical cyclone heat potential is ineffective for estimating hurricane strength in shallow water and demonstrates the importance of knowing subsurface temperatures if we want to improve hurricane forecasts. The two cruises provided opportunities for a considerable number of graduate and undergraduate students to experience research at sea. The September cruise provided space for 15 MS and PhD students, 7 undergraduates, and 3 post-docs on the three legs. The November cruise had only one leg, and accommodated 4 graduates and 4 undergraduates. A graduate student was co-chief scientist during leg 1 of the September cruise, with junior faculty acting as chief and co-chief scientists during legs 2 and 3. The chief scientist for the November cruise was a junior research scientist. Several graduate students collected samples for their own research during each cruise, while undergraduates acted as watch keepers and learned how to sample for multiple parameters under the supervision of experienced seagoing researchers. These RAPID Awards by NSF provide incredible opportunites to conduct science when a disaster strikes. Science benefits greatly from this program. Last Modified: 04/13/2019 Submitted by: Anthony H Knap