Scientific Results from the 2018 & 2019 North Atlantic Hurricane Glider Picket Lines

Collaborative partnerships between NOAA, Navy, academics and industry have now twice organized a glider picket line along the North Atlantic tropical cyclone pathway starting in the Caribbean and extending both westward into the Gulf of Mexico and northward along the U.S. east coast. During the 2018 hurricane season, a total of 62 gliders, some dedicated hurricane gliders, others gliders of opportunity, participated in the program by providing their real-time data to the U.S. IOOS Glider Data Assembly Center (DAC). From there, over 120,000 temperature and salinity profiles were harvested by NDBC and sent via GTS to operational modeling centers where they were available for assimilation. Here we review some of the scientific highlights of the U.S. hurricane glider program, how these results have influenced the program evolution, and how the program is expanding internationally.

Along the Caribbean’s Lesser Antilles islands, the importance of the flow through the passages and its impact on the distribution of heat and Amazon/Orinoco freshwater was noted in 2018, prompting the addition of Doppler profilers on gliders deployed to monitor flows through the passages starting with the British territories in 2019. In the Mid Atlantic, two classes of ocean response were identified depending on hurricane track and duration. The mixing response to fast moving nearshore storms results in significant shear-induced mixing of highly stratified coastal waters confirmed in Large Eddy Simulation models, resulting in rapid ocean surface cooling and storm weakening. The rapid advection of bottom cold water offshore during slow moving offshore storms leaves warm water behind, resulting in an ocean contribution towards intensification. These processes were investigated with a glider in similarly stratified Korean waters in 2018 where the rapid ocean cooling and weakening of Typhoon Soulik was observed. In response, the 2019 Mid Atlantic sampling plan includes 5 gliders deployed on adjacent triangular paths beneath a regional-scale HF Radar array used to spatially map the thermocline depth (see talk by Cliff Watkins) during the second half of hurricane season.