Sunday, 22 January 2012
Offshore Environmental Differences Between Tornadic and Non-Tornadic Tropical Cyclones
Hall E (New Orleans Convention Center )
This study documents the near-shore environments of landfalling tropical cyclones to determine those regions within the offshore TC environment that are favorable for miniature supercell and tornado development. To accomplish this high-resolution GPS dropwindsondes data, acquired from the NOAA's Hurricane Research Division, are used. The dataset spans 2001-2008, and after quality control checks, contains 53 flights, amounting to 1099 individual sounding profiles. The tornado occurrence data for all of the TCs sampled was collected from the National Climatic Data Center. The goal was to determine which current operational environmental forecast parameters are indicative of a favorable environment of miniature supercells and tornadoes, expanding upon the works of McCaul (1991), Bogner et al. (2000), and Baker et al. (2009) and determine any differences between the chosen stratifications. To that end a combination of composite maps, soundings, and statistical analyses were conducted on the entire dataset and two sets of stratifications: basin of occurrence and tornadic frequency. The results showed that there are significant differences between the stratifications primarily in the northeast/right-front quadrant where the largest amount of tornado reports were located. They also showed that the composite mid-latitude forecast parameters were the most skilled. However, the results also highlighted the need for a set of TC-specific thresholds and a TC-specific composite parameter in order to provide more accurate predictions. These new thresholds were selected primarily from the statistical analysis of the tornadic frequency section. The new composite parameter and its components were selected from the most skilled forecast parameters. This new parameter was then tested against the current mid-latitude parameters and produced favorable results even when using their new TC-specific criteria.