Tropical cyclogenesis

Team Leader: Robert Rogers (AOML/HRD)

Team members:
Michael Montgomery (Naval Postgraduate School, AOML/HRD)

Objective:
While forecasts of tropical cyclone track have shown significant improvements in recent years, corresponding improvements in forecasts of tropical cyclone intensity have been much slower. The lack of improvement in intensity forecasting is the result of deficiencies in the numerical models (e.g., resolution limitation and parameterization inadequacies), deficiencies in the observations, and deficiencies in our basic understanding of the physical processes involved. The problem becomes even more acute for forecasting tropical cyclogenesis. While global models have shown some skill in recent years in predicting tropical cyclogenesis, our understanding of the physical processes involved remains limited, largely because observing genesis events is a difficult task. However, a key aspect of the NOAA Intensity Forecasting Experiment (IFEX) is the collection of observations during all portions of a tropical cyclone's lifecycle, particularly on the early lifecycle stages. This emphasis on the early stages of the lifecycle will provide an opportunity to observe several genesis events and improve our understanding of this key process, leading to better predictions of tropical cyclogenesis, organization, and intensification.

Since both tropical cyclogenesis and tropical cyclone intensity change can be defined by changes in low- and mid-level vorticity, knowledge of the processes that play a significant role in genesis will also advance our understanding of intensity change. A better understanding of the processes that lead to an increase in low- and mid-level cyclonic vorticity will also allow NHC to better monitor and forecast tropical cyclogenesis and intensity change, improvements that would be especially valuable for those events that threaten coastal areas. Data obtained by aircraft investigating potential genesis events will positively impact operations and research in other ways as well. The collection of three-dimensional data at all stages in a tropical cyclone's lifecycle is one of the key requirements for NCEP as a part of the IFEX experiment. Such data will provide information that will guide the development of balance assumptions and error covariance matrices important in the development of data assimilation schemes for models (i.e., HWRF) that will be used in these environments. They will also provide important datasets for evaluating the performance of HWRF. In addition to improving the understanding and forecasting of tropical cyclogenesis and intensity change, the proposed experiment will yield useful insight into the structure, growth and ultimately the predictability of the systems responsible for almost all of the weather-related destruction in the tropical Atlantic and East Pacific. Investigation of systems that fail to complete the genesis process will also result in a better understanding and prediction of easterly disturbances in general so that distinction can be better made between developing and non-developing tropical disturbances.

Milestones

• Collect radar, dropsonde, flight-level, and SFMR data within and around a tropical disturbance undergoing genesis with near-continuous temporal coverage.

Last modified: 8/28/2007