Drifting buoy deployments into Hurricane Dean, 2007

An array of 12 drifting buoys was successfully deployed into the path of Hurricane Dean by the 53rd Weather Reconnaissance Squadron from a WC-130J aircraft on August 19, 2007 as Dean traversed the Caribbean Sea. The array consisted of 8 ADOS drifters equipped with a thermistor chain carrying temperature sensors every 10 m to a depth of 150m and 4 Minimet buoys with pressure, sea surface temperature and wind observations. The Minimets were equipped with a hydrophone to measure ambient noise from which wind speed was derived and a vane/compass from which wind director was derived. On august 20, Dean passed directly over the array with all buoys reporting data, having survived not only the airborne buoy deployment, but the hurricane maximum winds in excess of 130 kt as well. Two buoys ceased functioning the following day, with the remainder transmitting data for the next several months. Data were transmitted in real time via Service Argos and the Global Telecommunications Network to the world, to the Environmental Modeling Center for model data ingest and to forecasters at the National Hurricane Center who were able to view the data within 1-3 hours of acquisition on their N-AWIPS display where observations were superimposed on GOES satellite images. It is intended that data sets such as this will be able to provide simultaneous inputs to the atmosphere and ocean components of the coupled HWRF modeling system, to Navy COAMPS and other models, and help improve tropical cyclone (TC) track and intensity forecasts in the future. The Dean deployment served as a test for ocean and surface data acquisition, real-time transmittal of data to forecasters for near-term warnings and to modeling centers for data ingest and as a template for future experimental and operational efforts to augment inner-core tropical cyclone observations in TC regions of the world.

The Dean buoy trajectories provided observations of mixed layer mean flow, illustrating near-inertial response patterns, cooling at the surface just right of track of 1.5C and warming by almost 2.0C to the right of the surface cold pool at a depth of 100 m. Wind speeds were measured to 50 kt, failing above that due to algorithm deficiencies, an issue to be addressed in future research. A complete record of surface pressure was obtained, helping to map surface conditions at the air-sea interface at the same time as the complex and changing ocean conditions in a region characterized by deep initial mixed layers.