Hurricane surgery in global model forecast fields

Abstract: Global analysis frequently produces two vortices for the same hurricane due to the position errors in the background (6 hour) forecast. One vortex is generated by the forecast field which is used as the first guess, another is generated by the synthetic data (or observation). The two close vortices can produce large errors in the hurricane forecast. In order to improve the global analysis, the hurricane model initialization scheme developed at GFDL was modified and used to split global model forecast field into environment field and hurricane component. The hurricane component is then relocated to the observational position from the forecast field which effectively reduce two vortices to one in the analysis field. We will show some positive results in the conference.