March 9 Hawaii Kona Low System Case Study

This case study provides an examination of the Kona Low pressure system and its large-scale atmospheric environment that was conducive toward the development of a relatively rare, unprecedented severe weather event on 9 March 2012 over Hawaii. The data used in this study was retrieved from the Mauna Kea Weather Center data archives. The Kona Low for this event was characterized as a cold frontal cyclogenesis/ trade wind easterly case. This phenomenon is a cold core, cut-off, subtropical cyclone that initially develops along a cold frontal boundary and generally tracks from east of the islands to west over the span of three to five days. This type of set up commonly produces severe thunderstorms, hail, heavy rains, large surf and swell, and waterspouts. In this study, it was discovered that an interaction of this subtropical system with another surface boundary in the form of a stationary front provided sufficient forcing for vertical ascent into a moist, unstable environment. This enhancement allowed for the development of a rare tropical supercell thunderstorm that produced an EF-0 tornado, in addition to shattering the previous 1-inch hail record with 4.5-inch hail recorded. Overall, while climatological research on Kona Low formations indicates that the seasonal timing of this event was not unexpected, the meteorological outcomes were quite anomalous.