DEVELOPMENT OF AN OBJECTIVE SCHEME TO ESTIMATE TROPICAL CYCLONE INTENSITY FROM DIGITAL GEOSTATIONARY SATELLITE INFRARED IMAGERY

The standard method for estimating the intensity of tropical cyclones is based on satellite observations (Dvorak technique) and is utilized operationally by tropical analysis centers around the world. The techn ique relies on image pattern recognition along with analyst interpreta tion of empirically based rules regarding the vigor and organization o f convection surrounding the storm center. While this method performs well enough in most cases to be employed operationally, there are situ ations when analyst judgment can lead to discrepancies between differe nt analysis centers estimating the same storm. In an attempt to elimin ate this subjectivity, a computer-based algorithm that operates object ively on digital infrared information has been developed. An original version of this algorithm (engineered primarily by the third author) h as been significantly modified and advanced to include selected ''Dvor ak rules,'' additional constraints, and a time-averaging scheme. This modified version, the Objective Dvorak Technique (ODT), is applicable to tropical cyclones that have attained tropical storm or hurricane st rength. The performance of the ODT is evaluated on cases from the 1995 and 1996 Atlantic hurricane seasons. Reconnaissance aircraft measurem ents of minimum surface pressure are used to validate the satellite-ba sed estimates. Statistical analysis indicates the technique to be comp etitive with, and in some cases superior to, the Dvorak-based intensit y estimates produced operationally by satellite analysts from tropical analysis centers. Further analysis reveals situations where the algor ithm needs improvement, and directions for future research and modific ations are suggested.