THE IMPACT OF OMEGA-DROPWINDSONDES ON OPERATIONAL HURRICANE TRACK FORECAST MODELS

Since 1982, the Hurricane Research Division (HRD) has conducted a seri es of experiments with research aircraft to enhance the number of obse rvations in the environment and the core of hurricanes threatening the United States. During these experiments, the National Oceanic and Atm ospheric Administration WP 3D aircraft crews release Omega dropwindson des (ODWs) at 15-20-min intervals along the flight track to obtain pro files of wind, temperature, and humidity between flight level and the sea surface. Data from the ODWs are transmitted back to the aircraft a nd then sent via satellite to the Tropical Prediction Center and the N ational Centers for Environmental Prediction (NCEP), where the observa tions become part of the operational database. This paper tests the hy pothesis that additional observations improve the objective track fore cast models that provide operational guidance to the hurricane forecas ters. The testing evaluates differences in forecast tracks from models run with and without the ODW data in a research mode at HRD, NCEP, an d the Geophysical Fluid Dynamics Laboratory. The middle- and lower-tro pospheric ODW data produce statistically significant reductions in 12- 60-h mean forecast errors. The error reductions, which range from 16% to 30%, are at least as large as the accumulated improvement in operat ional forecasts achieved over the last 20-25 years. This breakthrough provides strong experimental evidence that more comprehensive observat ions in the hurricane environment and core will lead to immediate impr ovements in operational forecast guidance.