Development of Balloon Systems for Continuous Measurement of Hurricane Eye Properties

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The destructive potential of tropical cyclones increases nonlinearly with their maximum wind speed, yet direct measurements of tropical cyclone intensity are only made in some Atlantic storms and these are made only a few times per day. At the same time, it is well known that very substantial fluctuations in intensity occur on time scales at least as small as 12 hours in association with concentric eyewall cycles. In all areas of the world except the North Atlantic, satellite-based techniques are used for estimating tropical cyclone intensity. These techniques are based mostly on characteristics of cloud shapes and distributions from visible and infrared imagery, and on inferences about eye thermal structure from infrared imagery whose time continuity is limited by polar orbit restrictions. There is little in the way of "ground truth" for evaluating satellite-based estimates outside the Atlantic region, and no claim has been made that such techniques are capable of detecting short period intensity fluctuations. This research is the second step in a two-phase project to develop an air-deployable drogued balloon for continuous measurements in hurricane eyes. In the first phase, the balloon system was developed and tested in controlled environments, in numerical simulations and, to a limited extent, in the field. The Phase II effort will pursue extensive field testing and potentially the experimental deployment in actual hurricanes. The system will report continuous measurements of eye characteristics, including central surface pressure, which is a strong indicator of storm intensity, and sea surface temperature, which has a strong influence on storm intensity change. The system will be deployed on an opportunistic basis from U.S. Air Force C-130 reconnaissance aircraft that routinely survey Atlantic hurricanes. Data acquired from the balloon system will provide for the first time a nearly continuous record of storm intensity, helping researchers and forecasters understand and predict short period variations in hurricane intensity. Such records can also be compared to the nearly continuous records of storm characteristics available from geostationary satellites, so that potentially the latter can be used in the future to detect short period changes in hurricane intensity. The ultimate goal of this project is to provide a manned aircraft- and UAV-deployable balloon system for continuous monitoring of tropical cyclones worldwide. If successful, this project will lead to the first continuous measurement of hurricane eye properties. This will provide forecasters with detailed information about the intensity of hurricanes in between aircraft reconnaissance missions, thereby helping them to provide more accurate warnings. It will also help researchers characterize and understand short-period fluctuations in hurricane intensity.