3C.1
MPI, shear and rapid intensification of hurricanes
Jay S. Hobgood, Ohio State University, Columbus, OH
Most major hurricanes undergo a period of rapid intensification. The ability to forecast the timing and magnitude of rapid intensification represents a major challenge. Although the process of rapid intensification is not well understood, analysis of satellite imagery and other data seems to indicate that tropical cyclones need to achieve a certain level of organization before rapid intensification can occur. This required level of organization might imply the existence of thresholds that represent necessary conditions for rapid intensification. Identification of the existence of these thresholds would improve the ability to predict rapid intensification.
This study presents the results of a study of hurricanes that exhibited a period of rapid intensification over the Atlantic Ocean from 1988-2001. In this study a tropical cyclone is assumed to have undergone a period of rapid intensification when the minimum sea level pressure in the best track data decreased by at least 24 hPa in a period of 24 hours. Examinations of storms that underwent a period of rapid intensification showed that most systems were category 1 hurricanes at the onset of rapid intensification. Analysis of sea surace temperatures (SSTs) confirms that rapid intensification occurred when SSTs were warm enough to support the development and intensification of tropical cyclones. Data from the NCEP/NCAR reanalysis was used to compute the Maximum Potential Intensity (MPI) and vertical wind shear prior to the onset of rapid intensification. Some storms approached their MPI by the end of the period of rapid intensification. Analysis of the wind shear indicated little wind shear prior to the onset of rapid intensification in some cases. The results of this study suggest that it may be difficult to identify absolute thresholds that would provide useful indications to forecasters prior to rapid intensification. However, it may be possible to develop relative thresholds that combine the state of the tropical cyclone and the conditions in the surrounding environment.
Session 3C, Tropical Cyclone Intensity Change II (Parallel with Sessions 3A, 3B, & 3D)
Monday, 29 April 2002, 4:00 PM-5:30 PM
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