The forecasting of rapid changes in tropical cyclone intensity has been particularly difficult and was recently highlighted by the unexpected weakening of Hurricane Debby (2000) along the northern coast of Hispaniola on August 23, 2000. Debby moved across the northeast Caribbean Sea making landfall near Barbuda and later near St. Barthelmy in the British Virgin Islands with minimal damage. However, several operational GFDL runs pointed toward Debby moving over southeast Florida and becoming a significant threat to the gold coast. The increasing threat of a dangerous hurricane prompted authorities in the Florida Keys to initiate evacuations of all non-residents resulting in a significant loss of tourism for that area. Debby never struck the continental United States and dissipated harmlessly in the western Caribbean Sea. However, this case represents an overwhelming reminder of the limitations associated with tropical cyclone intensity forecasting. The purpose of this paper is to investigate the role of environmental factors involved in the sudden weakening of Hurricane Debby (2000) and possible reasons for the tendency of the operational GFDL model to consistently forecast intensification. Increasing southwest shear appears to be the primary catalyst for the sudden weakening of Debby. Accordingly, the GFDL forecast shear is compared with shear calculations from UW-CIMSS. Additionally, the forecast wind field from the model is compared/verified with a suite of data sources including satellite-derived winds, upper-air data, and dropwindsondes from a NOAA G-IV synoptic surveillance mission.