JTWC 5-Day Operational Tropical Cyclone Wind Radii Forecasting - First Year in Review

JTWC operationalized five-day forecasts of tropical cyclone (TC) wind structure (four-quadrant 34, 50 and 64 knot wind radii) in November 2016. This change was made possible largely as a result of recently developed analysis and forecast TC structure guidance. In the year since, JTWC has observed an improvement in overall structure forecast error and biases, consistent with results from pre-implementation testing and evaluation. Additionally, forecast and best-track TC growth now exhibits greatly smoothed profiles throughout the storm lifecycle, including during the period of extra-tropical transition. DOD customers have benefited from more realistic depictions of the area of potential 34-knot winds (i.e., the U.S. Navy ship avoidance swath) and improved specification of 50-knot winds used in setting Tropical Cyclone Conditions of Readiness (TCCORs). Furthermore, improvements in structure forecasts also have impacts in the generation on downstream applications (e.g., wind probabilities and WaveWatch III runs based on official forecasts). This talk will discuss some impacts and lessons learned during the first year of 5-day wind radii forecasting, post-storm re-analysis of tropical cyclone structure data at JTWC, and caveats for use of these data in studies.