Application of the Dvorak technique at JTWC for estimating tropical cyclone intensity

In the decades since its inception in the 1970’s, the Dvorak technique has been used operationally across the globe to subjectively derive tropical cyclone intensity, including at the Joint Typhoon Warning Center (JTWC). JTWC is responsible for tracking and forecasting tropical cyclones for the U.S. Department of Defense and other government agencies operating from the east coast of Africa to the dateline in the northern hemisphere and across the south Indian and Pacific oceans. Altogether, this area of responsibility comprises 65-million square miles of oceans, accounting for nearly three-quarters of global tropical cyclone activity annually. JTWC’s Satellite Operations (SATOPS) department contributes to this mission by providing detailed analyses of storm position, structure, and intensity through the employment of the Dvorak technique on imagery from the Meteosat-9, EWS-G1, Himawari-9, GK-2A, and GOES-18 satellites. Conducting an average of 10,000 fixes annually, SATOPS plays an especially critical role because routine aerial reconnaissance is largely unavailable. These fixes help to establish the parameters with which models are initialized. Some agencies have adapted a more purist approach to the technique, while others have made regional modifications. JTWC applies Vernon Dvorak’s 1984 revision with several important adjustments, which will be presented in this talk. We will also highlight ways that technological advancements have played in improving both subjective and objective Dvorak estimates, as well as some significant challenges that remain. Finally, we will look at a few noteworthy examples.